CHAPTER XVI

GLACIAL FEATURES

THE SNOWLINE

South America is classical ground in the study of tropical snowlines. The African mountains that reach above the snowline in the equatorial belt--Ruwenzori, Kibo, and Kenia--have only been studied recently because they are remote from the sea and surrounded by bamboo jungle and heavy tropical forest. On the other hand, many of the tropical mountains of South America lie so near the west coast as to be visible from it and have been studied for over a hundred years. From the days of Humboldt (1800) and Boussingault (1825) down to the present, observations in the Andes have been made by an increasing number of scientific travelers. The result is a large body of data upon which comparative studies may now be profitably undertaken.

Like scattered geographic observations of many other kinds, the earlier studies on the snowline have increased in value with time, because the snowline is a function of climatic elements that are subject to periodic changes in intensity and cannot be understood by reference to a single observation. Since the discovery of physical proofs of climatic changes in short cycles, studies have been made to determine the direction and rate of change of the snowline the world over, with some very striking results.

It has been found[55] that the changes run in cycles of from thirty to thirty-five years in length and that the northern and southern hemispheres appear to be in opposite phase. For example, since 1885 the snowline in the southern hemisphere has been decreasing in elevation in nine out of twelve cases by the average amount of nine hundred feet. With but a single exception, the snowline in the northern hemisphere has been rising since 1890 with an average increase of five hundred feet in sixteen cases. To be sure, we must recognize that the observations upon which these conclusions rest have unequal value, due both to personal factors and to differences in instrumental methods, but that in spite of these tendencies toward inequality they should agree in establishing a general rise of the snowline in the northern hemisphere and an opposite effect in the southern is of the highest significance.

It must also be realized that snowline observations are altogether too meager and scattered in view of the abundant opportunities for making them, that they should be standardized, and that they must extend over a much longer period before they attain their full value in problems in climatic variations. Once the possible significance of snowline changes is appreciated the number and accuracy of observations on the elevation and local climatic relations of the snowline should rapidly increase.

In 1907 I made a number of observations on the height of the snowline in the Bolivian and Chilean Andes between latitudes 17° and 20° south, and in 1911 extended the work northward into the Peruvian Andes along the seventy-third meridian. It is proposed here to assemble these observations and, upon comparison with published data, to make a few interpretations.

From Central Lagunas, Chile, I went northeastward via Pica and the Huasco Basin to Llica, Bolivia, crossing the Sillilica Pass in May, 1907, at 15,750 feet (4,800 m.). Perpetual snow lay at an estimated height of 2,000-2,500 feet above the pass or 18,000 feet (5,490 m.) above the sea. Two weeks later the Huasco Basin, 14,050 feet (4,280 m.), was covered a half-foot deep with snow and a continuous snow mantle extended down to 13,000 feet. Light snows are reported from 12,000 feet, but they remain a few hours only and are restricted to the height of exceptionally severe winter seasons (June and early July). Three or four distant snow-capped peaks were observed and estimates made of the elevation of the snowline between the Cordillera Sillilica and Llica on the eastern border of the Maritime Cordillera. All observations agreed in giving an elevation much in excess of 17,000 feet. In general the values run from 18,000 to 19,000 feet (5,490 to 5,790 m.). Though the bases of these figures are estimates, it should be noted that a large part of the trail lies between 14,000 and 16,000 feet, passing mountains snow-free at least 2,000 to 3,000 feet higher, and that for general comparisons they have a distinct value.

In the Eastern Cordillera of Bolivia, snow was observed on the summit of the Tunari group of peaks northwest of Cochabamba. Steinmann, who visited the region in 1904, but did not reach the summit of the Tunari group of peaks, concludes that the limit of perpetual snow should be placed above the highest point, 17,300 (5,270 m.); but in July and August, 1907, I saw a rather extensive snow cover over at least the upper 1,000 feet, and what appeared to be a very small glacier. Certain it is that the Cochabamba Indians bring clear blue ice from the Tunari to the principal hotels, just as ice is brought to Cliza from the peaks above Arani. On these grounds I am inclined to place the snowline at 17,000 feet (5,180 m.) near the eastern border of the Eastern Cordillera, latitude 17° S. At 13,000 feet, in July, 1907, snow occurred in patches only on the pass called Abre de Malaga, northeast of Colomi, 13,000 feet, and fell thickly while we were descending the northern slopes toward Corral, so that in the early morning it extended to the cold timber line at 10,000 feet. In a few hours, however, it had vanished from all but the higher and the shadier situations.

In the Vilcanota knot above the divide between the Titicaca and Vilcanota hydrographic systems, the elevation of the snowline was 16,300+ feet (4,970 m.) in September, 1907. On the Cordillera Real of Bolivia it is 17,000 to 17,500 feet on the northeast, but falls to 16,000 feet on the southwest above La Paz. In the first week of July, 1911, snow fell on the streets of Cuzco (11,000 feet) and remained for over an hour. The heights north of San Geronimo (16,000 feet) miss the limit of perpetual snow and are snow-covered only a few months each year.

In taking observations on the snowline along the seventy-third meridian I was fortunate enough to have a topographer the heights of whose stations enabled me to correct the readings of my aneroid barometer whenever these were taken off the line of traverse. Furthermore, the greater height of the passes--15,000 to 17,600 feet--brought me more frequently above the snowline than had been the case in Bolivia and Chile. More detailed observations were made, therefore, not only upon the elevation of the snowline from range to range, but also upon the degree of canting of the snowline on a given range. Studies were also made on the effect of the outline of the valleys upon the extent of the glaciers, the influence on the position of the snowline of mass elevation, precipitation, and cloudiness.

Snow first appears at 14,500 feet (4,320 m.) on the eastern flanks of the Cordillera Vilcapampa, in 13° south latitude. East of this group of ridges and peaks as far as the extreme eastern border of the mountain belt, fifty miles distant, the elevations decrease rapidly to 10,000 feet and lower, with snow remaining on exceptionally high peaks from a few hours to a few months. In the winter season snow falls now and then as low as 11,500 feet, as in the valley below Vilcabamba pueblo in early September, 1911, though it vanishes like mist with the appearance of the sun or the warm up-valley winds from the forest. Storms gather daily about the mountain summits and replenish the perpetual snow above 15,000 feet. In the first pass above Puquiura we encountered heavy snow banks on the northeastern side a hundred feet below the pass (14,500 feet), but on the southwestern or leeward side it is five hundred feet lower. This distribution is explained by the lesser insolation on the southwestern side, the immediate drifting of the clouds from the windward to the leeward slopes, and to the mutual intensification of cause and effect by topographic changes such as the extension of collecting basins and the steeping of the slopes overlooking them with a corresponding increase in the duration of shade.

It is well known that with increase of elevation and therefore of the rarity of the air there is less absorption of the sun’s radiant energy, and a corresponding increase in the degree of insolation. It follows, therefore, that at high altitudes the contrasts between sun and shade temperatures will increase. Frankland[56] has shown that the increase may run as high as 500 per cent between 100 to 10,000 feet above the sea. I have noted a fall of temperature of 15° F. in six minutes, due to the obscuring of the sun by cloud at an elevation of 16,000 feet above Huichihua in the Central Ranges of Peru. Since the sun shines approximately half the time in the snow-covered portions of the mountains and since the tropical Andes are of necessity snow-covered only at lofty elevations, this contrast between shade and sun temperatures is by far the most powerful factor influencing differences in elevation of the snowline in Peru.

To the drifting of the fallen snow is commonly ascribed a large portion of this contrast. I have yet to see any evidence of its action near the snowline, though I have often observed it, especially under a high wind in the early morning hours at considerable elevations above the snowline, as at the summits of lofty peaks. It appears that the lower ranges bearing but a limited amount of snow are not subject to drifting because of the wetness of the snow, and the fact that it is compacted by occasional rains and hail storms. Only the drier snow at higher elevations and under stronger winds can be effectively dislodged.

The effect of unequal distribution of precipitation on the windward and leeward slopes of a mountain range is in general to depress the snowline on the windward slopes where the greater amount falls, but this may be offset in high altitudes by temperature contrasts as in the westward trending Cordillera Vilcapampa, where north and south slopes are in opposition. If the Cordillera Vilcapampa ran north and south we should have the windward and leeward slopes equally exposed to the sun and the snowline would lie at a lower elevation on the eastern side. Among all the ranges the slopes have decreasing precipitation to the leeward, that is, westerly. The second and third passes, between Arma and Choquetira, are snow-free (though their elevations equal those of the first pass) because they are to leeward of the border range, hence receive less precipitation. The depressive effect of increased precipitation on the snowline is represented by A-B, Fig. 184; in an individual range the effect of heavier precipitation may be offset by temperature contrasts between shady and sunny slopes, as shown by the line a-b in the same figure.

The degree of canting of the snowline on opposite slopes of the Cordillera Vilcapampa varies between 5° and 12°, the higher value being represented four hours southwest of Arma on the Choquetira trail, looking northeast. A general view of the Cordillera looking east at this point (Fig. 186), shows the appearance of the snowline as one looks along the flanks of the range. In detail the snowline is further complicated by topography and varying insolation, each spur having a snow-clad and snow-free aspect as shown in the last figure. The degree of difference on these minor slopes may even exceed the difference between opposite aspects of the range in which they occur.

To these diversifying influences must be added the effect of warm up-valley winds that precede the regular afternoon snow squalls and that melt the latest fall of snow to exceptionally high elevations on both the valley floor and the spurs against which they impinge. The influence of the warmer air current is notably confined to the heads of those master valleys that run down the wind, as in the valley heading at the first pass, Cordillera Vilcapampa, and at the heads of the many valleys terminating at the passes of the Maritime Cordillera. Elsewhere the winds are dissipated in complex systems of minor valleys and their effect is too well distributed to be recognized.

It is clear from the conditions of the problem as outlined on preceding pages that the amount of canting may be expressed in feet of difference of the snowline on opposite sides of a range or in degrees. The former method has, heretofore, been employed. It is proposed that this method should be abolished and degrees substituted, on the following grounds: Let _A_ and _B_, Fig. 190, represent two mountain masses of unequal area and unequal elevation. Let the opposite ends of the snowlines of both figures lie 1,000 feet apart as between the windward and leeward sides of a broad cordillera (A), or as between the relatively sunnier and relatively shadier slopes of individual mountains or narrow ranges in high latitudes or high altitudes (B). With increasing elevation there is increasing contrast between temperatures in sunshine and in shade, hence a greater degree of canting (B). Tending toward a still greater degree of contrast is the effect of the differences in the amounts of snowy precipitation, which are always more marked on an isolated and lofty mountain summit than upon a broad mountain mass (1) because in the former there is a very restricted area where snow may accumulate, and (2) because with increase of elevation there is a rapid and differential decrease in both the rate of adiabatic cooling and the amount of water vapor; hence the snow-producing forces are more quickly dissipated.

Furthermore, the leeward side of a lofty mountain not only receives much less snow proportionally than the leeward side of a lower mountain, but also loses it faster on account of the smaller extent of surface upon which it is disposed and the proportionally larger extent of counteractive, snow-free surface about it. Among the volcanoes of Ecuador are many that show differences of 500 feet in snowline elevation on windward and leeward (east) slopes and some, as for example Chimborazo, that exhibit differences of 1,000 feet. The latter figure also expresses the differences in the broad Cordillera Vilcapampa and in the Maritime Cordillera, though the _rate_ of canting as expressed in degrees is much greater in the case of the western mountains.

The advantages of the proposed method of indicating the degree of canting of the snowline lie in the possibility thus afforded of ultimately separating and expressing quantitatively the various factors that affect the position of the line. In the Cordillera Vilcapampa, for example, the dominant canting force is the difference between sun and shade temperatures, while in the volcanoes of Ecuador, where _symmetrical volcanoes, almost on the equator, have equal insolation on all aspects_ and the temperature contrasts are reduced to a minimum--the differences are owing chiefly to varying exposure to the winds. The elusive factors in the comparison are related to the differences in area and in elevation.

The value of arriving finally at close snowline analyses grows out of (1) the possibility of snowline changes in short cycles and (2) uncertainty of arriving by existing methods at the snowline of the glacial period, whose importance is fundamental in refined physiographic studies in glaciated regions with a complex topography. To show the application of the latter point we shall now attempt to determine the snowline of the glacial period in the belt of country along the route of the Expedition.

In the group of peaks shown in Fig. 188 between Lambrama and Antabamba, the elevation of the snowline varies from 16,000 to 17,000 feet (4,880-5,180 m.), depending on the topography and the exposure. The determination of the limit of perpetual snow was here, as elsewhere along the seventy-third meridian, based upon evidences of nivation. It will be observed in Fig. 191 that just under the snow banks to the left of the center are streams of rock waste which head in the snow. Their size is roughly proportional to the size of the snow banks, and, furthermore, they are not found on snow-free slopes. From these facts it is concluded that they represent the waste products of snow erosion or nivation, just as the hollows in which the snow lies represent the topographic products of nivation. On account of the seasonal and annual variation in precipitation and temperature--hence in the elevation of the snowline--it is often difficult to make a correct snowline observation based upon depth and _apparent_ permanence. Different observers report great changes in the snowline in short intervals, changes not explained by instrumental variations, since they are referred to topographic features. It appears to be impossible to rely upon present records for small changes possibly related to minor climatic cycles because of a lack of standardization of observations.

Nothing in the world seems simpler at first sight than an observation on the elevation of the snowline. Yet it can be demonstrated that large numbers of observers have merely noted the position of temporary snow. It is strongly urged that evidences of nivation serve henceforth as proof of permanent snow and that photographic records be kept for comparison. In this way measurements of changes in the level of the snowline may be accurately made and the snow cover used as a climatic gauge.

Farther west in the Maritime Cordillera, the snowline rises to 18,000 feet on the northern slopes of the mountains and to 17,000 feet on the southern slopes. The top of the pass above Cotahuasi, 17,600 feet (5,360 m.), was snow-free in October, 1911, but the snow extended 500 feet lower on the southern slope. The degree of canting is extraordinary at this point, single volcanoes only 1,500 to 2,000 feet above the general level and with bases but a few miles in circumference exhibit a thousand feet of difference in the snowline upon northern and southern aspects. This is to be attributed no less to the extreme elevation of the snow (and, therefore, stronger contrasts of shade and sun temperatures) than to the extreme aridity of the region and the high daytime temperatures. The aridity is a factor, since heavy snowfall means a lengthening of the period of precipitation in which a cloud cover shuts out the sun and a shortening of the period of insolation and melting.

Contrasts between shade and sun temperatures increase with altitude but their effects also increase in _time_. Of two volcanoes of equal size and both 20,000 feet above sea level, that one will show the greater degree of canting that is longer exposed to the sun. The high daytime temperature is a factor, since it tends to remove the thinnest snow, which also falls in this case on the side receiving the greatest amount of heat from the sun. The high daytime temperature is phenomenal in this region, and is owing to the great extent of snow-free land at high elevations and yet below the snowline, and to the general absence of clouds and the thinness of vegetation.

On approach to the western coast the snowline descends again to 17,500 feet on Coropuna. There are three chief reasons for this condition. First, the well-watered Majes Valley is deeply incised almost to the foot of Coropuna, above Chuquibamba, and gives the daily strong sea breeze easy access to the mountain. Second, the Coast Range is not only low at the mouth of the Majes Valley, but also is cut squarely across by the valley itself, so that heavy fogs and cloud sweep inland nightly and at times completely cover both valley and desert for an hour after sunrise. Although these yield no moisture to the desert or the valley floor except such as is mechanically collected, yet they do increase the precipitation upon the higher elevations at the valley head.

A third factor is the size of Coropuna itself. The mountain is not a simple volcano but a composite cone with five main summits reaching well above the snowline, the highest to an elevation of 21,703 feet (6,615 m.). It measures about 20 miles (32 km.) in circumference at the snowline and 45 miles (72 km.) at its base (measuring at the foot of the steeper portion), and stands upon a great tributary lava plateau from 15,000 to 17,000 feet above sea level. Compared with El Misti, at Arequipa, its volume is three times as great, its height two thousand feet more, and its access to ocean winds at least thirty per cent more favorable. El Misti, 19,200 feet (5,855 m.) has snow down as far as 16,000 feet in the wet season and rarely to 14,000 feet, though by sunset a fall of snow may almost disappear whose lower limit at sunrise was 16,000 feet. Snow may accumulate several thousand feet below the summit during the wet season, and in such quantities as to require almost the whole of the ensuing dry season (March to December) for its melting. Northward of El Misti is the massive and extended range, Chachani, 20,000 feet (6,100 m.) high; on the opposite side is the shorter range called Pichu-Pichu. Snow lies throughout the year on both these ranges, but in exceptional seasons it nearly disappears from Chachani and wholly disappears from Pichu-Pichu, so that the snowline then rises to 20,000 feet. It is considered that the mean of a series of years would give a value between 17,000 and 18,000 feet for the snowline on all the great mountains of the Arequipa region.[57] This would, however, include what is known to be temporary snow; the limit of “perpetual” snow, or the true snowline, appears to lie about 19,000 feet on Chachani and _above_ El Misti, say 19,500 feet. It is also above the crest of Pichu-Pichu. The snowline, therefore, appears to rise a thousand feet from Coropuna to El Misti, owing chiefly to the poorer exposure of the latter to the sources of snowy precipitation.

It may also be noted that the effect of the easy access of the ocean winds in the Coropuna region is also seen in the increasing amount of vegetation which appears in the most favorable situations. Thus, along the Salamanca trail only a few miles from the base of Coropuna are a few square kilometers of _quenigo_ woodland generally found in the cloud belt at high altitudes; for example, at 14,000 feet above Lambrama and at 9,000 feet on the slope below Incahuasi, east of Pasaje. The greater part of the growth is disposed over hill slopes and on low ridges and valley walls. It is, therefore, clearly unrelated as a whole to the greater amount of ground-water with which a part is associated, as along the valley floors of the streams that head in the belt of perpetual snow. The appearance of this growth is striking after days of travel over the barren, clinkery lava plateau to eastward that has a less favorable exposure. The _quenigo_ forest, so-called, is of the greatest economic value in a land so desolate as the vast arid and semi-arid mountain of western Peru. Every passing traveler lays in a stock of fire-wood as he rests his beasts at noonday; and long journeys are made to these curious woodlands from both Salamanca and Chuquibamba to gather fuel for the people of the towns.

NIVATION

The process of nivation, or snow erosion, does not always produce visible effects. It may be so feeble as to make no impression upon very resistant rock where the snow-fall is light and the declivity low. Ablation may in such a case account for almost the whole of the snow removed. On strong and topographically varied slopes where the snow is concentrated in headwater alcoves, there is a more pronounced downward movement of the snow masses with more prominent effects both of erosion beneath the snow and of accumulation at the border of the snow. In such cases the limit of perpetual snow may be almost as definitely known as the limit of a glacier. Like glaciers these more powerful snow masses change their limits in response to regional changes in precipitation, temperature, or both. It would at first sight appear impossible to distinguish between these changes through the results of nivation. Yet in at least a few cases it may be as readily determined as the past limits of glaciers are inferred from the terminal moraines, still intact, that cross the valley floors far below the present limits of the ice.

In discussing the process of nivation it is necessary to assume a sliding movement on the part of the snow, though it is a condition in Matthes’ original problem in which the nivation idea was introduced that the snow masses remain stationary. It is believed, however, that Matthes’ valuable observations and conclusions really involve but half the problem of nivation; or at the most but one of two phases of it. He has adequately shown the manner in which that phase of nivation is expressed which we find _at the border of the snow_. Of the action _beneath_ the snow he says merely: “Owing to the frequent oscillations of the edge and the successive exposure of the different parts of the site to frost action, the area thus affected will have no well-defined boundaries. The more accentuated slopes will pass insensibly into the flatter ones, and the general tendency will be to give the drift site a cross section of smoothly curved outline and ordinarily concave.”[58]

From observations on the effects of nivation in valleys, Matthes further concludes that “on a grade of about 12 per cent ... névé must attain a thickness of at least 125 feet in order that it may have motion,”[59] though as a result of the different line of observations Hobbs concludes[60] that a somewhat greater thickness is required.

The snow cover in tropical mountains offers a number of solid advantages in this connection. Its limits, especially on the Cordillera Vilcapampa, on the eastern border of the Andes, are subject to _small seasonal oscillations_ and the edge of the “perpetual” snow is easily determined. Furthermore, it is known from the comparatively “fixed quality of tropical climate,” as Humboldt put it, that the variations of the snowline in a period of years do not exceed rather narrow limits. In mid-latitudes on the contrary there is an extraordinary shifting of the margin of the snow cover, and a correspondingly wide distribution of the feeble effects of nivation.

Test cases are presented in Figs. 191, 192, and 193, Cordillera Vilcapampa, for the determination of the fact of the movement of the snow long before it has reached the thickness Matthes or Hobbs believes necessary for a movement of translation to begin. Fig. 191 shows snow masses occupying pockets on the slope of a ridge that was never covered with ice. Past glacial action with its complicating effects is, therefore, excluded and we have to deal with snow action pure and simple. The pre-glacial surface with smoothly contoured slopes is recessed in a noteworthy way from the ridge crest to the snowline of the glacial period at least a thousand feet lower. The recesses of the figure are peculiar in that not even the largest of them involve the entire surface from top to bottom; they are of small size and are scattered over the entire slope. This is believed to be due to the fact that they represent the limits of variations of the snowline in short cycles. Below them as far as the snowline of the glacial period are larger recesses, some of which are terminated by masses of waste as extensive as the neighboring moraines, but disposed in irregular scallops along the borders of the ridges or mountain slopes in which the recesses have been found.

The material accumulated at the lower limit of the snow cover of the glacial period was derived from two sources: (1) from slopes and cliffs overlooking the snow, (2) from beneath the snow by a process akin to ice plucking and abrasion. The first process is well known and resembles the shedding of waste upon a valley glacier or a névé field from the bordering cliffs and slopes. Material derived in this manner in many places rolls down a long incline of snow and comes to rest at the foot of it as a fringe of talus. The snow is in this case but a substitute for a normal mass of talus. The second process produces its most clearly recognizable effects on slopes exceeding a declivity of 20°; and upon 30° and 40° slopes its action is as well-defined as true glacial action which it imitates. It appears to operate in its simplest form as if independent of the mass of the snow, small and large snow patches showing essentially the same results. This is the reverse of Matthes’ conclusion, since he says that though the minimum thickness “must vary inversely with the percentage of the grade,” “the influence of the grade is inconsiderable,” and that the law of variation must depend upon additional observation.[61]

Let us examine a number of details and the argument based upon them and see if it is not possible to frame a satisfactory law of variation.

In Fig. 193 the chief conditions of the problem are set forth. Forward from the right-hand peak are snow masses descending to the head of a talus (_A_) whose outlines are clearly defined by freshly fallen snow. At (_B_) is a glacier whose tributaries descend the middle and left slopes of the picture after making a descent from slopes several thousand feet higher and not visible in this view. The line beneath the glacier marks the top of the moraine it has built up. Moraines farther down valley show a former greater extent of the glacier. Clearly the talus material at (_A_) was accumulated after the ice had retreated to its present position. It will be readily seen from an inspection of the photograph that the total amount of material at (_A_) is an appreciable fraction of that in the moraine. The ratio appears to be about 1:8 or 1:10. I have estimated that the total area of snow-free surface about the snowfields of the one is to that of the other as 2:3. The gradients are roughly equivalent, but the volume of snow in the one case is but a small fraction of that in the other. It will be seen that the snow masses have recessed the mountain slopes at _A_ and formed deep hollows and that the hollowing action appears to be most effective where the snow is thickest.

Summarizing, we note first, that the roughly equivalent factors are gradient and amount of snow-free surface; second, that the unequal factors are (a) accumulated waste, (b) degree of recessing, and (c) the degree of compacting of snow into ice and a corresponding difference in the character of the glacial agent, and (d) the extent of the snow cover. The direct and important relation of the first two unequal factors to the third scarcely need be pointed out.

We have then an inequality in amount of accumulated material to be explained by either an inequality in the extent of the snow and therefore an inequality of snow action, or an inequality due to the presence of ice in one valley and not in the other, or by both. It is at once clear that if ice is absent above (_A_) and the mountain slopes are recessed that snow action is responsible for it. It is also recognized that whatever rate of denudation be assigned to the snow-free surfaces this rate must be exceeded by the rate of snow action, else the inequalities of slope would be decreased rather than increased. The accumulated material at (_A_) is, therefore, partly but not chiefly due to denudation of snow-free surfaces. It is due chiefly to _erosion_ beneath the snow. Nor can it be argued that the hollows now occupied by snow were formed at some past time when ice not snow lay in them. They are not ice-made hollows for they are on a steep spur above the limits of ice action even in the glacial period. Any past action is, therefore, represented here in _kind_ by present action, though there would be differences in _degree_ because the heavier snows of the past were displaced by the lighter snows of today.

While it appears that the case presents clear proof of degradation by snow it is not so clear how these results were accomplished. Real abrasion on a large scale as in bowlder-shod glaciers is ruled out, since glacial striæ are wholly absent from nivated surfaces according to both Matthes’ observations and my own. Yet all nivated surfaces have very distinctive qualities, delicately organized slopes which show a marked change from any original condition related to water-carving. In the absence of striæ, the general absence of all but a thin coating of waste _even in rock hollows_, and the accumulation of waste up to bowlders in size at the lower edge of the nivated zone, I conclude that compacted snow or névé of sufficient thickness and gradient may actually pluck rock outcrops in the same manner though not at the rate which ice exhibits. That the products of nivation may be bowlders as well as fine mud would seem clearly to follow increase in effectiveness, due to increase in amount of the accumulated snow; that bowlders are actually transported by snow is also shown by their presence on the lower margins of nivated tracts.

Our argument may be made clearer by reference to the observed action of snow in a particular valley. Snow is shed from the higher, steeper slopes to the lower slopes and eventually accumulates to a marked degree on the bottoms of the depressions, whence it is avalanched down valley over a series of irregular steps on the valley floor. An avalanche takes place through the breaking of a section of snow just as an iceberg breaks off the end of a tide-water glacier. Evidently there must be pressure from behind which crowds the snow forward and precipitates it to a lower level.

As a snow mass falls it not only becomes more consolidated, beginning at the plane of impact, but also gives a shock to the mass upon which it falls that either starts it in motion or accelerates its rate of motion. The action must therefore be accompanied by a drag upon the floor and if the rock be close-jointed and the blocks, defined by the joint planes, small enough, they will be transported. Since snow is not so compact as ice and permits included blocks easily to adjust themselves to new resistances, we should expect the detached blocks included in the snow to change their position constantly and to form irregular scratches, but not parallel striæ of the sort confidently attributed to stone-shod ice.

It is to the plasticity of snow that we may look for an explanation of the smooth-contoured appearance of the landscape in the foreground of Fig. 135. The smoothly curved lines are best developed where the entire surface was covered with snow, as in mid-elevations in the larger snowfields. At higher elevations, where the relief is sharper, the snow is shed from the steeper declivities and collected in the minor basins and valley heads, where its action tends to smooth a floor of limited area, while snow-free surfaces retain all their original irregularities of form or are actually sharpened.

The degree of effectiveness of snow and névé action may be estimated from the reversed slopes now marked by ponds or small marshy tracts scattered throughout the former névé fields, and the many niched hollows. They are developed above Pampaconas in an admirable manner, though their most perfect and general development is in the summit belt of the Cordillera Vilcapampa between Arma and Choquetira, Fig. 135. It is notable in _all_ cases where nivation was associated with the work of valley glaciers that the rounded nivated slopes break rather sharply with the steep slopes that define an inner valley, whose form takes on the flat floor and under-cut marginal walls normal to valley glaciation.

A classification of numerous observations in the Cordillera Vilcapampa and in the Maritime Cordillera between Lambrama and Antabamba may now be presented as the basis for a tentative expression of the law of variation respecting snow motion. The statement of the law should be prefaced by the remark that thorough checking is required under a wider range of conditions before we accept the law as final. Near the lower border of the snow where rain and hail and alternate freezing and thawing take place, the snow is compacted even though but fifteen to twenty feet thick, and appears to have a down-grade movement and to exercise a slight drag upon its floor when the gradient does not fall below 20°. Distinct evidences of nivation were observed on slopes with a declivity of 5° near summit areas of past glacial action, where the snow did not have an opportunity to be alternately frozen and thawed.

The _thickness_ of the former snow cover could, however, not be accurately determined, but was estimated from the topographic surroundings to have been at least several hundred feet. Upon a 40° slope a snow mass 50 feet thick was observed to be breaking off at a cliff-face along the entire cross-section as if impelled forward by thrust, and to be carrying a small amount of waste--enough distinctly to discolor the lowermost layers--which was shed upon the snowy masses below. With increase in the degree of compactness of the snow at successively lower elevations along a line of snow discharge, gradients down to 25° were still observed to carry strongly crevassed, waste-laden snow down to the melting border. It appeared from the clear evidences of vigorous action--the accumulation of waste, the strong crevassing, the stream-like character of the discharging snow, and the pronounced topographic depression in which it lay--that much flatter gradients would serve, possibly not more than 15°, for a snow mass 150 feet wide, 30 to 40 feet thick, and serving as the outlet for a set of tributary slopes about a square mile in area and with declivities ranging from small precipices to slopes of 30°.

We may say, therefore, that the factors affecting the rate of motion are (1) thickness, (2) degree of compactness, (3) diurnal temperature changes, and (4) gradient. Among these, diurnal temperature changes operate indirectly by making the snow more compact and also by inducing motion directly. At higher elevations above the snowline, temperature changes play a decreasingly important part. The thickness required varies inversely as the gradient, and upon a 20° slope is 20 feet for wet and compact snow subjected to alternate freezing and thawing. For dry snow masses above the zone of effective diurnal temperature changes, an increasing gradient is required. With a gradient of 40°, less than 50 feet of snow will move _en masse_ if moderately compacted under its own weight; if further compacted by impact of falling masses from above, the required thickness may diminish to 40 feet and the required declivity to 15°. The gradient may decrease to 0° or actually be reversed and motion still continue provided the compacting snow approach true névé or even glacier ice as a limit.

From the sharp topographic break between the truly glaciated portions of the valley in regions subjected to temporary glaciation, it is concluded that the eroding power of the moving mass is suddenly increased at the point where névé is finally transformed into true ice. This transformation must be assumed to take place suddenly to account for so sudden a change of function as the topographic break requires. Below the point at which the transformation occurs the motion takes place under a new set of conditions whose laws have already been formulated by students of glaciology.

The foregoing readings of gradient and depth of snow are typical of a large number which were made in the Peruvian Andes and which have served as the basis of Fig. 195. It will be observed that between 15° and 20° there is a marked change of function and again between +5° and -5° declivity, giving a double reversed curve. The meaning of the change between 15° and 20° is inferred to be that, with gradients over 20°, snow cannot wholly resist gravity in the presence of diurnal temperature changes across the freezing point and occasional snow or hail storms. With increase of thickness compacting appears to progress so rapidly as to permit the transfer of thrust for short distances before absorption of thrust takes place in the displaced snow. At 250 feet thorough compacting appears to take place, enabling the snow to move out under its own weight on even the faintest slopes; while, with a thickness still greater, the resulting névé may actually be forced up slight inclines whose declivity appears to approach 5° as a limit. I have nowhere been able to find in truly nivated areas reversed curves exceeding 5°, though it should be added that depressions whose leeward slopes were reversed to 2° and 3° are fairly common. If the curve were continued we should undoubtedly find it again turning to the left at the point where the thickness of the snow results in the transformation of snow to ice. From the sharp topographic break observed to occur in a narrow belt between the névé and the ice, it is inferred that the erosive power of the névé is to that of the ice as 2:4 or 1:5 _for equal areas_; and that reversed slopes of a declivity of 10° to 15° may be formed by glaciers is well known. Precisely what thickness of snow or névé is necessary and what physical conditions effect its transformation into ice are problems not included in the main theme of this chapter.

It is important that the proposed curve of snow motion under minimum conditions be tested under a large variety of circumstances. It may possibly be found that each climatic region requires its special modifications. In tropical mountains the sudden alternations of freezing and thawing may effect such a high degree of compactness in the snow that lower minimum gradients are required than in the case of mid-latitude mountains where the perpetual snow of the high and cold situations is compacted through its own weight. Observations of the character introduced here are still unattainable, however. It is hoped that they will rapidly increase as their significance becomes apparent; and that they have high significance the striking nature of the curve of motion seems clearly to establish.

BERGSCHRUNDS AND CIRQUES

The facts brought out by the curve of snow-motion (Fig. 195) have an immediate bearing on the development of cirques, whose precise mode of origin and development have long been in doubt. Without reviewing the arguments upon which the various hypotheses rest, we shall begin at once with the strongest explanation--W. D. Johnson’s famous bergschrund hypothesis. The critical condition of this hypothesis is the diurnal migration across the freezing point of the air temperature at the bottom of the schrund. Alternate freezing and thawing of the water in the joints of the rock to which the schrund leads, exercise a quarrying effect upon the rock and, since this effect is assumed to take place at the foot of the cirque, the result is a steady retreat of the steep cirque wall through basal sapping.

While Johnson’s hypothesis has gained wide acceptance and is by many regarded as the final solution of the cirque problem it has several weaknesses in its present form. In fact, I believe it is but one of two factors of equal importance. In the first place, as A. C. Andrews[62] has pointed out, it is extremely improbable that the bergschrund of glacial times under the conditions of a greater volume of snow could have penetrated to bedrock at the base of the cirque where the present change of slope takes place. In the second place, the assumption is untenable that the bergschrund in all cases reaches to or anywhere near the foot of the cirque wall. A third condition outside the hypothesis and contradictory to it is the absence of a bergschrund in snowfields at many valleys heads where cirques are well developed!

Johnson himself called attention to the slender basis of observation upon which his conclusions rest. In spite of his own caution with respect to the use of his meager data, his hypothesis has been applied in an entirely too confident manner to all kinds of cirques under all kinds of conditions. Though Johnson descended an open bergschrund to a rock floor upon which ice rested, his observations raise a number of proper questions as to the application of these valuable data: How long are bergschrunds open? How often are they open? Do they everywhere open to the foot of the cirque wall? Are they present for even a part of the year in all well-developed cirques? Let us suppose that it is possible to find many cirques filled with snow, not ice, surrounded by truly precipitous walls and with an absence of bergschrunds, how shall we explain the topographic depressions excavated underneath the snow? If cirque formation can be shown to take place without concentrated frost action at the foot of the bergschrund, then is the bergschrund not a secondary rather than a primary factor? And must we not further conclude that when present it but hastens an action which is common to all snow-covered recesses?

It is a pleasure to say that we may soon have a restatement of the cirque problem from the father of the bergschrund idea. The argument in this chapter was presented orally to him after he had remarked that he was glad to know that some one was finding fault with his hypothesis. “For,” he said, with admirable spirit, “I am about to make a most violent attack upon the so-called Johnson hypothesis.” I wish to say frankly that while he regards the following argument as a valid addition to the problem, he does not think that it solves the problem. There are many of us who will read his new explanation with the deepest interest.

We shall begin with the familiar fact that many valleys, now without perpetual snow, formerly contained glaciers from 500 to 1,000 feet thick and that their snowfields were of wide extent and great depth. At the head of a given valley where the snow is crowded into a small cross-section it is compacted and suffers a reduction in its volume. At first nine times the volume of ice, the gradually compacting névé approaches the volume of ice as a limit. At the foot of the cirque wall we may fairly assume in the absence of direct observations, a volume reduction of one-half due to compacting. But this is offset in the case of a well-developed cirque by volume increases due to the convergence of the snow from the surrounding slopes, as shown in Fig. 196. Taking a typical cirque from a point above Vilcabamba pueblo I find that the radius of the trough’s end is to the radius of the upper wall of the cirque as 1:4; and since the corresponding surfaces are to one another as the squares of their similar dimensions we have 1:4 or 1:16 as the ratio of their snow areas. If no compacting took place, then to accommodate all the snow in the glacial trough would require an increase in thickness in the ratio of 1:4. If the snow were compacted to half its original volume then the ratio would be 1:2. Now, since the volume ratio of ice to snow is 1:9 and the thickness of the ice down valley is, say 400 feet, the equivalent of loose snow at the foot of the cirque must be more than 1:4 over 1:9 or more than two and one-quarter times thicker, or 400 feet thick; and would give a pressure of (900 ÷ 10) × 62.5 pounds, or 5,625 pounds, or a little less than three tons per square foot. Since a pressure of 2,500 pounds per square foot will convert snow into ice at freezing temperature, it is clear that ice and not snow was the state at the bottom of the mass in glacial times. Further, between the surface of the snow and the surface of the bottom layer of the ice there must have been every gradation between loose snow and firm ice, with the result that a thickness much less than 900 feet must be assumed. Precisely what thickness would be found at the foot of the cirque wall is unknown. But granting a thickness of 400 feet of ice an additional 300 feet for névé and snow would raise the total to 700 feet.

The application of the facts in the above paragraph is clearly seen when we refer to Fig. 197. The curve of snow motion of Fig. 195 is applied to an unglaciated mountain valley. Taking a normal snow surface and filling the valley head it is seen that the excess of snow depth over the amount required to give motion is a measure at various points in the valley head and at different gradients of the erosive force of the snow. It is strikingly concentrated on the 15°-20° gradient which is precisely where the so-called process of basal sapping is most marked. If long continued the process will lead to the developing of a typical cirque for it is a process that is self-stimulating. The more the valley is changed in form the more it tends to change still further in form because of deepening snowfields until cliffed pinnacles and matterhorns result.

By further reference to the figure it is clear that a schrund 350 feet deep could not exist on a cirque wall with a declivity of even 20° without being closed by flow, unless we grant _more rapid flow_ below the crevasse. In the case of a glacier flowing over a nearly flat bed away from the cirque it is difficult to conceive of a rate of flow greater than that of snow and névé on the steep lower portion of the cirque wall, when movement on that gradient _begins_ with snow but 20 feet thick.

In contrast to this is the view that the schrund line should lie well up the cirque wall where the snow is comparatively thin and where there is an approach to the lower limits of movement. The schrund would appear to open where the bottom material changes its form, i.e., where it first has its motion accelerated by transformation into névé. In this view the schrund opens not at the foot of the cirque wall but well above it as in Fig. 198, in which _C_ represents snow from top to bottom; _B_, névé; and _A_, ice. The required conditions are then (1) that the steepening of the cirque wall from _x_ to _y_ should be effected by sapping originated at _y_ through the agencies outlined by Johnson; (2) that the steepening from _x_ to _y_ should be effected by sapping originated at _x_ through the change of the agent from névé to ice with a sudden change of function; (3) and that the essential unity of the wall _x-y-z_ be maintained through the erosive power of the névé, which would tend to offset the formation of a shelf along a horizontal plane passed through _y_. The last-named process not only appears entirely reasonable from the conditions of gradient and depth outlined on pp. 296 to 298, but also meets the actual field conditions in all the cases examined in the Peruvian Andes. This brings up the second and third of our main considerations, that the bergschrund does not always or even in many cases reach the foot of the cirque wall, and that cirques exist in many cases where bergschrunds are totally absent.

It is a striking fact that frost action at the bottom of the bergschrund has been assumed to be the only effective sapping force, in spite of the common observation that bergschrunds lie in general well toward the upper limits of snowfields--so far, in fact, that their bottoms in general occur several hundred feet above the cirque floors. Is the cirque under these circumstances a result of the schrund or is the schrund a result of the cirque? _In what class of cirques do schrunds develop?_ If cirque development in its early stages is not marked by the development of bergschrunds, then are bergschrunds an _essential_ feature of cirques in their later stages, however much the sapping process may be hastened by schrund formation?

Our questions are answered at once by the indisputable facts that many schrunds occur well toward the upper limit of snow, and that many cirques exist whose snowfields are not at all broken by schrunds. It was with great surprise that I first noted the bergschrunds of the Central Andes, especially after becoming familiar with Johnson’s apparently complete proof of their genetic relation to the cirques. But it was less surprising to discover the position of the few observed--high up on the cirque walls and always near the upper limit of the snowfields.

A third fact from regions once glaciated but now snow-free also combined with the two preceding facts in weakening the wholesale application of Johnson’s hypothesis. In many headwater basins the cirque whose wall at a distance seemed a unit was really broken into two unequal portions; a lower, much grooved and rounded portion and an upper unglaciated, steep-walled portion. This condition was most puzzling in view of the accepted explanation of cirque formation, and it was not until the two first-named facts and the applications of the curves of snow motion were noted that the meaning of the break on the cirque became clear. Referring to Fig. 198 we see at once that the break occurs at _y_ and means that under favorable topographic and geologic conditions sapping at _y_ takes place faster than at _x_ and that the retreat of _y-z_ is faster than _x-y_. It will be clear that when these conditions are reversed or sapping at _x_ and at _y_ are equal a single wall will result. On reference to the literature I find that Gilbert recently noted this feature and called it the _schrundline_.[63] He believes that it marks the base of the bergschrund _at a late stage in the excavation of the cirque basin_. He notes further that the lower less-steep slope is glacially scoured and that it forms “a sort of shoulder or terrace.”

If all the structural and topographic conditions were known in a great variety of gathering basins we should undoubtedly find in them, and not in special forms of ice erosion, an explanation of the various forms assumed by cirques. The limitations inherent in a high-altitude field and a limited snow cover prevented me from solving the problem, but it offered sufficient evidence at least to indicate the probable lines of approach to a solution. For example it is noteworthy that in _all_ the cases examined the schrundline was better developed the further glacial erosion had advanced. So constantly did this generalization check up, that if at a distance a short valley was observed to end in a cirque, I knew at once and long before I came to the valley head that a shoulder below the schrundline did not exist. At the time this observation was made its significance was a mystery, but it represents a condition so constant that it forms one of the striking features of the glacial forms in the headwater region.

The meaning of this feature is represented in Fig. 199, in which three successive stages in cirque development are shown. In _A_, as displayed in small valleys or mountainside alcoves which were but temporarily occupied by snow and ice, or as in all higher valleys during the earlier stages of the advancing hemicycle of glaciation, snow collects, a short glacier forms, and a bergschrund develops. As a result of the concentrated frost action at the base of the bergschrund a rapid deepening and steepening takes place at _a_. As long as the depth of snow (or snow and névé) is slight the bergschrund may remain open. But its existence at this particular point is endangered as the cirque grows, since the increasing steepness of the slope results in more rapid snow movement. Greater depth of snow goes hand in hand with increasing steepness and thus favors the formation of névé and even ice at the bottom of the moving mass and a constantly accelerated rate of motion. At the same time the bergschrund should appear higher up for an independent reason, namely, that it tends to form between a mass of slight movement and one of greater movement, which change of function, as already pointed out, would appear to be controlled by change from snow to névé or ice on the part of the bottom material.

The first stages in the upward migration of the bergschrund will not effect a marked change from the original profile, since the converging slopes, the great thickness of névé and ice at this point, and the steep gradient all favor powerful erosion. When, however, stage _C_ is reached, and the bergschrund has retreated to _c″_, a broader terrace results below the schrundline, the gradient is decreased, the ice and névé (since they represent a constant discharge) are spread over a greater area, hence are thinner, and we have the cirque taking on a compound character with a lower, less steep and an upper, precipitous section.

It is clear that a closely jointed and fragile rock might be quarried by moving ice at _c′-c″_ and the cirque wall extended unbroken to _x_; it is equally clear that a homogeneous, unjointed granite would offer no opportunities for glacial plucking and would powerfully resist the much slower process of abrasion. Thus Gilbert[64] observed the schrundline in the granites of the Sierra Nevada, which are “in large part structureless” and my own observations show the schrundline well developed in the open-jointed granites of the Cordillera Vilcapampa and wholly absent in the volcanoes of the Maritime Cordillera, where ashes and cinders, the late products of volcanic action, form the easily eroded walls of the steep cones. Somewhere between these extremes--lack of a variety of observations prevents our saying where--the resistance and the internal structure of the rock will just permit a cirque wall to extend from _x_ to _c′ ″_ of Fig. 199.

A common feature of cirques that finds an explanation in the proposed hypothesis is the notch that commonly occurs at some point where a convergence of slopes above the main cirque wall concentrates snow discharge. It is proposed to call this type the notched cirque. It is highly significant that these notches are commonly marked by even steeper descents at the point of discharge into the main cirque than the remaining portion of the cirque wall, even when the discharge was from a very small basin and in the form of snow or at the most névé. The excess of discharge at a point on the basin rim ought to produce the form we find there under the conditions of snow motion outlined in earlier paragraphs. It is also noteworthy that it is at such a point of concentrated discharge that crevasses no sooner open than they are closed by the advancing snow masses. To my mind the whole action is eminently representative of the action taking place elsewhere along the cirque wall on a smaller scale.

What seems a good test of the explanation of cirques here proposed was made in those localities in the Maritime Cordillera, where large snowbanks but not glaciers affect the form of the catchment basins. A typical case is shown in Fig. 201. As in many other cases we have here a great lava plateau broken frequently by volcanic cones of variable composition. Some are of lava, others consist of ashes, still others of tuff and lava and ashes. At lower elevations on the east, as at 16,000 feet between Antabamba and Huancarama, evidences of long and powerful glaciers are both numerous and convincing. But as we rise still higher the glaciated topography is buried progressively deeper under the varying products of volcanic action, until finally at the summit of the lava fields all evidences of glaciation disappear in the greater part of the country between Huancarama and the main divide. Nevertheless, the summit forms are in many cases as significantly altered as if they had been molded by ice. Precipitous cirque walls surround a snow-filled amphitheater, and the process of deepening goes forward under one’s eyes. No moraines block the basin outlets, no U-shaped valleys lead forward from them. We have here to do with post-glacial action pure and simple, the volcanoes having been formed since the close of the Pleistocene.

Likewise in the pass on the main divide, the perpetual snow has begun the recessing of the very recent volcanoes bordering the pass. The products of snow action, muds and sands up to very coarse gravel, glaciated in texture with an intermingling of blocks up to six inches in diameter in the steeper places, are collected into considerable masses at the snowline, where they form broad sheets of waste so boggy as to be impassable except by carefully selected routes. No ice action whatever is visible below the snowline and the snow itself, though wet and compact, is not underlain by ice. Yet the process of hollowing goes forward visibly and in time will produce serrate forms. In neither case is there the faintest sign of a bergschrund; the gradients seem so well adjusted to the thickness and rate of movement of the snow from point to point that the marginal crack found in many snowfields is absent.

The absence of bergschrunds is also noteworthy in many localities where formerly glaciation took place. This is notoriously the case in the summit zone of the Cordillera Vilcapampa, where the accumulating snows of the steep cirque walls tumble down hundreds of feet to gather into prodigious snowbanks or to form névé fields or glaciers. From the converging walls the snowfalls keep up an intermittent bombardment of the lower central snow masses. It is safe to say that if by magic a bergschrund could be opened on the instant, it would be closed almost immediately by the impetus supplied by the falling snow masses. The explanation appears to be that the thicker snow and névé concentrated at the bottom of the cirque results in a corresponding concentration of action and effect; and cirque development goes on without reference to a bergschrund. The chief attraction of the bergschrund hypothesis lies in the concentration of action at the foot of the cirque wall. But in the thickening of the snow far beyond the minimum thickness required for motion at the base of the cirque wall and its change of function with transformation into névé, we need invoke no other agent. If a bergschrund forms, its action may take place at the foot of the cirque wall or high up on the wall, and yet _sapping at the foot of the wall_ continue.

From which we conclude (1) that where frost action occurs at the bottom of a bergschrund opening to the foot of the cirque wall it aids in the retreat of the wall; (2) that a sapping action takes place at this point whether or not a bergschrund exists and that bergschrund action is not a _necessary_ part of cirque formation; (3) that when a more or less persistent bergschrund opens on the cirque wall above its foot it tends to develop a schrundline with a marked terrace below it; (4) that schrundlines are best developed in the mature stages of topographic development in the glacial cycle; (5) that the varying rates of snow, névé, and ice motion at a valley head are the _persistent_ features to which we must look for topographic variations; (6) that the hypothesis here proposed is applicable to all cases whether they involve the presence of snow or névé or ice or any combination of these, and whether bergschrunds are present or not; and (7) at the same time affords a reasonable explanation for such variations in forms as the compound cirque with its schrundline and terrace, the unbroken cirque wall, the notched cirque, and the recessed, snow-covered mountain slopes unaffected by ice.

ASYMMETRICAL CREST LINES AND ABNORMAL VALLEY PROFILES IN THE CENTRAL ANDES

To prove that under similar conditions glacial erosion may be greater than subaërial denudation quantitative terms must be sought. Only these will carry conviction to the minds of many opponents of the theory that ice is a vigorous agent of erosion. Gilbert first showed in the Sierra Nevada that headwater glaciers eroded more rapidly than nonglacial agents under comparable topographic and structural conditions.[65] Oddly enough none of the supporters of opposing theories have replied to his arguments; instead they have sought evidence from other regions to show that ice cannot erode rock to an important degree. In this chapter evidence from the Central Andes, obtained in 1907 and 1911, will be given to show the correctness of Gilbert’s proposition.

The data will be more easily understood if Gilbert’s argument is first outlined. On the lower slopes of the glaciated Sierra Nevada asymmetry of form resulted from the presence of ice on one side of each ridge and its absence on the other (Fig. 200). The glaciers of these lower ridges were the feeblest in the entire region and were formed on slopes of small extent; they were also short-lived, since they could have existed only when glacial conditions had reached a maximum. Let the broken line in the upper part of the figure represent the preglacial surface and the solid line beneath it the present surface. It will not matter what value we give the space between the two lines on the left to express nonglacial erosion, since had there been no glaciers it would be the same on both sides of the ridge. The feeble glacier occupying the right-hand slope was able in a very brief period to erode a depression far deeper than the normal agents of denudation were able to erode in a much longer period, i.e., during all of interglacial and postglacial time. Gilbert concludes: “The visible ice-made hollows, therefore, represent the local excess of glacial over nonglacial conditions.”

In the Central Andes are many volcanic peaks and ridges formed since the last glacial epoch and upon them a remarkable asymmetry has been developed. Looking southward one may see a smoothly curved, snow-free, northward-facing slope rising to a crest line which appears as regular as the slope leading to it. Looking northward one may see by contrast (Fig. 194) sharp ridges, whose lower crests are serrate, separated by deeply recessed, snow-filled mountain hollows. Below this highly dissected zone the slopes are smooth. The smooth slope represents the work of water; the irregular slopes are the work of snow and ice. The relation of the north and south slopes is diagrammatically shown in Fig. 201.

To demonstrate the erosive effects of snow and ice it must be shown: (1) that the initial slopes of the volcanoes are of postglacial age; (2) that the asymmetry is not structural; (3) that the snow-free slopes have not had special protection, as through a more abundant plant cover, more favorable soil texture, or otherwise.

Proof of the postglacial origin of the volcanoes studied in this connection is afforded: (1) by the relation of the flows and the ash and cinder beds about the bases of the cones to the glacial topography; (2) by the complete absence of glacial phenomena below the present snowline. Ascending a marginal valley (Fig. 202), one comes to its head, where two tributaries, with hanging relations to the main valley, come down from a maze of lesser valleys and irregular slopes. Glacial features of a familiar sort are everywhere in evidence until we come to the valley heads. Cirques, reversed grades, lakes, and striæ are on every hand. But at altitudes above 17,200 feet, recent volcanic deposits have over large areas entirely obscured the older glacial topography. The glacier which occupied the valley of Fig. 202 was more than one-quarter of a mile wide, the visible portion of its valley is now over six miles long, but the extreme head of its left-hand tributary is so concealed by volcanic material that the original length of the glacier cannot be determined. It was at least ten miles long. From this point southward to the border of the Maritime Cordillera no evidence of past glaciation was observed, save at Solimana and Coropuna, where slight changes in the positions of the glaciers have resulted in the development of terminal moraines a little below the present limits of the ice.

From the wide distribution of glacial features along the northeastern border of the Maritime Cordillera and the general absence of such features in the higher country farther south, it is concluded that the last stages of volcanic activity were completed in postglacial time. It is equally certain, however, that the earlier and greater part of the volcanic material was ejected before glaciation set in, as shown by the great depth of the canyons (over 5,000 feet) cut into the lava flows, as contrasted with the relatively slight filling of coarse material which was accumulated on their floors in the glacial period and is now in process of dissection. Physiographic studies throughout the Central Andes demonstrate both the general distribution of this fill and its glacial origin.

So recent are some of the smaller peaks set upon the lava plateau that forms the greater part of the Maritime Cordillera, that the snows massed on their shadier slopes have not yet effected any important topographic changes. The symmetrical peaks of this class are in a few cases so very recent that they are entirely uneroded. Lava flows and beds of tuff appear to have originated but yesterday, and shallow lava-dammed lakes retain their original shore relations. In a few places an older topography, glacially modified, may still be seen showing through a veneer of recent ash and cinder deposits, clear evidence that the loftier parts of the lava plateau were glaciated before the last volcanic eruption.

The asymmetry of the peaks and ridges in the Maritime Cordillera cannot be ascribed to the manner of eruption, since the contrast in declivity and form is persistently between northern and southern slopes. Strong and persistent winds from a given direction undoubtedly influence the form of volcanoes to at least a perceptible degree. In the case in hand the ejectamenta are ashes, cinders, and the like, which are blown into the air and have at least a small component of motion down the wind during both their ascent and descent. The _prevailing_ winds of the high plateaus are, however, easterly and the strongest winds are from the west and blow daily, generally in the late afternoon. Both wind directions are at right angles to the line of asymmetry, and we must, therefore, rule out the winds as a factor in effecting the slope contrasts which these mountains display.

It remains to be seen what influence a covering of vegetation on the northern slopes might have in protecting them from erosion. The northern slopes in this latitude (14° S.) receive a much greater quantity of heat than the southern slopes. Above 18,000 feet (5,490 m.) snow occurs on the shady southern slopes, but is at least a thousand feet higher on the northern slopes. It is therefore absent from the northern side of all but the highest peaks. Thus vegetation on the northern slopes is not limited by snow. Bunch grass--the characteristic _ichu_ of the mountain shepherds--scattered spears of smaller grasses, large ground mosses called _yareta_, and lichens extend to the snowline. This vegetation, however, is so scattered and thin above 17,500 feet (5,330 m.) that it exercises no retarding influence on the run-off. Far more important is the porous nature of the volcanic material, which allows the rainfall to be absorbed rapidly and to appear in springs on the lower slopes, where sheets of lava direct it to the surface.

The asymmetry of the north and south slopes is not, then, the result of preglacial erosion, of structural conditions, or of special protection of the northern slopes from erosion. It must be concluded, therefore, that it is due to the only remaining factor--snow distribution. The southern slopes are snow-clad, the northern are snow-free--in harmony with the line of asymmetry. The distribution of the snow is due to the contrasts between shade and sun temperatures, which find their best expression in high altitudes and on single peaks of small extent. Frankland’s observations with a black-bulb thermometer _in vacuo_ show an increase in shade and sun temperatures contrasts of over 40° between sea level and an elevation of 10,000 feet. Violle’s experiments show an increase of 26 per cent in the intensity of solar radiation between 200 feet and 16,000 feet elevation. Many other observations up to 16,000 feet show a rapid increase in the difference between sun and shade temperatures with increasing elevation. In the region herein described where the snowline is between 18,000 and 19,000 feet (5,490 to 5,790 m.) these contrasts are still further heightened, especially since the semi-arid climate and the consequent long duration of sunshine and low relative humidity afford the fullest play to the contrasting forces. The coefficient of absorption of radiant energy by water vapor is 1,900 times that of air, hence the lower the humidity the more the radiant energy expended upon the exposed surface and the greater the sun and shade contrasts. The effect of these temperature contrasts is seen in a canting of the snowline on individual volcanoes amounting to 1,500 feet in extreme instances. The average may be placed at 1,000 feet.

The minimum conditions of snow motion and the bearing of the conclusions upon the formation of cirques have been described in the chapters immediately preceding. It is concluded that snow moves upon 20° slopes if the snow is at least forty feet deep, and that through its motion under more favorable conditions of greater depth and gradient and the indirect effects of border melting there is developed a hollow occupied by the snow. Actual ice is not considered to be a necessary condition of either movement or erosion. We may at once accept the conclusion that the invariable association of the cirques and steepened profiles with snowfields proves that snow is the predominant modifying agent.

An argument for glacial erosion based on profiles and steep cirque walls in a volcanic region has peculiar appropriateness in view of the well-known symmetrical form of the typical volcano. Instead of varied forms in a region of complex structure long eroded before the appearance of the ice, we have here simple forms which immediately after their development were occupied by snow. _Ever since their completion these cones have been eroded by snow on one side and by water on the other._ If snow cannot move and if it protects the surface it covers, then this surface should be uneroded. All such surfaces should stand higher than the slopes on the opposite aspect eroded by water. But these assumptions are contrary to fact. The slopes underneath the snow are deeply recessed; so deeply eroded indeed, that they are bordered by steep cliffs or cirque walls. The products of erosion also are to some extent displayed about the border of the snow cover. In strong contrast the snow-free slopes are so slightly modified that little of their original symmetry is lost--only a few low hills and shallow valleys have been formed.

The measure of the excess of snow erosion over water erosion is therefore the difference between a northern or water-formed and a southern or snow-formed profile, Fig. 200. This difference is also shown in Fig. 201 and from it and the restored initial profiles we conclude that the rate of water erosion is to that of nivation as 1:3. This ratio has been derived from numerous observations on cones so recently formed that the interfluves without question are still intact.

Thus far only those volcanoes have been considered which have been modified by nivation. There are, however, many volcanoes which have been eroded by ice as well as by snow and water. It will be seen at once that where a great area of snow is tributary to a single valley, the snow becomes compacted into névé and ice, and that it then erodes at a much faster rate. Also a new force--plucking--is called into action when ice is present, and this greatly accelerates the rate of erosion. While it lies outside the limits of my subject to determine quantitatively the ratio between water and ice action, it is worth pointing out that by this method a ratio much in excess of 1:3 is determined, which even in this rough form is of considerable interest in view of the arguments based on the protecting influence of both ice and snow. I have, indeed, avoided the question of ice erosion up to this point and limited myself to those volcanoes which have been modified by nivation only, since the result is more striking in view of the all but general absence of data relating to this form of erosion.

If we now turn to the valley profiles of the glaciated portions of the Peruvian Andes, we shall see the excess of ice over water erosion expressed in a manner equally convincing. To a thoughtful person it is one of the most remarkable features of any glaciated region that the flattest profiles, the marshiest valley flats, and the most strongly meandering stretches of the streams should occur near the heads of the valleys. The mountain shepherds recognize this condition and drive their flocks up from the warmer valley into the mountain recesses, confident that both distance and elevation will be offset by the extensive pastures of the finest _ichu_ grass. Indeed, to be near the grazing grounds of sheep and llamas which are their principal means of subsistence, the Indians have built their huts at the extraordinarily lofty elevations of 16,000 to 17,000 feet.

An examination of a large number of these valleys and the plotting of their gradients discloses the striking fact that the heads of the valleys were deeply sunk into the mountains. It is thus possible by restoring the preglacial profiles to measure with considerable certainty the excess of ice over water erosion.

The results are graphically expressed in Fig. 202. It will be seen that until glacial conditions intervened the stream was flowing on a rock floor. During the whole of glacial time it was aggrading its rock floor below _b′_ and forming a deep valley fill. A return to warmer and drier conditions led to the dissection of the fill and this is now in progress. The stream has not yet reached its preglacial profile, but it has almost reached it. We may, therefore, say that the preglacial valley profile below _b′_ fixes the position of the present profile just as surely as if the stream had been magically halted in its work at the beginning of the period of glaciation. There, _b′-d-c-b_ represents the amount of ice erosion. To be sure the line _b-c_ is inference, but it is reasonable inference and, whatever position is assigned to it, it cannot be coincident with _b′-d_, nor can it be anywhere near it. The break in the valley profile at _b′_ is always marked by a terminal moraine, regardless of the character of the rock. This is not an accidental but a causal association. It proves the power of the ice to erode. In glacial times it eroded the quantity _b-c-d-b′_. This is not an excess of ice over water erosion, but an absolute measure of ice erosion, since _a′-b′_ has remained intact. The only possible error arises from the position assigned _b-c_, and even if we lower it to _b-c′_ (for which we have no warrant but extreme conservatism) we shall still have left _b′-c′-d-b_ as a striking value for rock erosion (plucking and abrasion) by a valley glacier.

A larger diagram, Fig. 203, represents in fuller detail the topographic history of the Andes of southern Peru and the relative importance of glaciation. The broad spurs with grass-covered tops that end in steep scarps are in wonderful contrast to the serrate profiles and truncated spurs that lie within the zone of past glaciation. In the one case we have minute irregularities on a canyon wall of great dimensions; in the other, more even walls that define a glacial trough with a flat floor. Before glaciation on a larger scale had set in the right-hand section of the diagram had a greater relief. It was a residual portion of the mountain and therefore had greater height also. Glaciers formed upon it in the Ice Age and glaciation intensified the contrast between it and the left-hand section; not so much by intensifying the relief as by diversifying the topographic forms.

APPENDIX A

SURVEY METHODS EMPLOYED IN THE CONSTRUCTION OF THE SEVEN ACCOMPANYING TOPOGRAPHIC SHEETS

BY KAI HENDRIKSEN, TOPOGRAPHER

The main part of the topographical outfit consisted of (1) a 4-inch theodolite, Buff and Buff, the upper part detachable, (2) an 18 x 24 inch plane-table with Johnson tripod and micro-meteralidade. These instruments were courteously loaned the expedition by the U. S. Coast and Geodetic Survey and the U. S. Geological Survey respectively.

The method of survey planned was a combination of graphic triangulation and traverse with the micro-meteralidade. All directions were plotted on the plane-table which was oriented by backsight; distances were determined by the micro-meteralidade or triangulation, or both combined; and elevations were obtained by vertical angles. Finally, astronomical observations, usually to the sun, were taken at intervals of about 60 miles for latitude and azimuth to check the triangulation. No observations were made for differences in longitude because this would probably not have given any reliable result, considering the time and instruments at our disposal. Because the survey was to follow very closely the seventy-third meridian west of Greenwich, directions and distances, checked by latitude and azimuth observations, undoubtedly afforded far better means of determining the longitude than time observations. In other words, the time observations made in connection with azimuth observations were not used for computing longitudinal differences. Absolute longitude was taken from existing observations of principal places.

Principal topographical points were located by from two to four intersections from the triangulation and plane-table stations; and elevations were determined by vertical angle measurements. Whenever practicable, the contours were sketched in the field; the details of the topography otherwise depend upon a great number of photographs taken by Professor Bowman from critical stations or other points which it was possible to locate on the maps.

CROSS-SECTION MAP FROM ABANCAY TO CAMANÁ AT THE PACIFIC OCEAN

Seven sheets. Scale, 1:125,000; contour interval, 200 feet. Datum is mean sea level. Astronomical control: 5 latitude and 5 azimuth observations as indicated on the accompanying topographic sheets.

On September 10th, returning from a reconnaissance survey of the Pampaconas River, I joined Professor Bowman’s party, Dr. Erving acting as my assistant. We crossed the Cordillera Vilcapampa and the Canyon of the Apurimac and after a week’s rest at Abancay started the topographic work near Hacienda San Gabriel south of Abancay. Working up the deep valley of Lambrama, observations for latitude and azimuth were made midway between Hacienda Matara and Caypi.

On October 4th we made our camp in newly fallen snow surrounded by beautiful glacial scenery. The next day on the high plateau, we passed sharp-crested glaciated peaks; a heavy thunder and hail storm broke out while I occupied the station at the pass, the storm continuing all the afternoon--a frequent occurrence. The camp was made 6 miles farther on, and the next morning I returned to finish the latter station. I succeeded in sketching the detailed topography just south of the pass, but shortly after noon, a furious storm arose similar to the one the day before, and made further topographic work impossible; to get connection farther on I patiently kept my eye to the eye-piece for more than an hour after the storm had started, and was fortunate to catch the station ahead in a single glimpse. I had a similar experience some days later at station 16,079, Antabamba Quadrangle, on the rim of the high-level puna, the storm preventing all topographic work and barely allowing a single moment in which to catch a dim sight of the signals ahead while I kept my eye steadily at the telescope to be ready for a favorable break in the heavy clouds and hail.

At Antabamba we got a new set of Indian carriers, who had orders to accompany us to Cotahuasi, the next sub-prefectura. Raimondi’s map indicates the distance between the two cities to be 35 miles, but although nothing definite was stated, we found out in Antabamba that the distance was considerably longer, and moreover that the entire route lay at a high altitude.

From the second day out of Antabamba until Huaynacotas was in sight in the Cotahuasi Canyon, a distance of 50 miles, the route lay at an altitude of from 16,000 to 17,630 feet, taking in 5 successive camps at an altitude from 15,500 to 17,000 feet; 12 successive stations had the following altitudes:

16,379 feet 16,852 " 17,104 " 17,559 " 17,675 " --highest station occupied. 17,608 " 17,633 " 16,305 " 17,630 " 17,128 " 16,794 " 16,260 "

The occupation of these high stations necessitated a great deal of climbing, doubly hard in this rarefied air, and often on volcanoes with a surface consisting of bowlders and ash and in the face of violent hailstorms that made extremely difficult the task of connecting up observations at successive stations.

At Cotahuasi a new pack-train was organized, and on October 25th I ventured to return alone to the high altitudes in order to continue the topography at the station at 17,633 feet on the summit of the Maritime Cordillera. Dr. Erving was obliged to leave on October 18th and Professor Bowman left a week later in order to carry out his plans for a physiographic study of the coast between Camaná and Mollendo. Philippi Angulo, a native of Taurisma, a town above Cotahuasi, acted as majordomo on this journey. Knowing the trail and the camp sites, I was able to pick out the stations ahead myself, and made good progress, returning to Cotahuasi on October 29th, three or four days earlier than planned. From Cotahuasi to the coast I had the assistance of Mr. Watkins. The most trying part of the last section of high altitude country was the great Pampa Colorada, crowned by the snow-capped peaks of Solimana and Coropuna, reaching heights of 20,730 and 21,703 feet respectively. The passing of this pampa took seven days and we arrived at Chuquibamba on November 9th. Two circumstances made the work on this stretch peculiarly difficult--the scarcity of camping places and the high temperature in the middle of the day, which heated the rarefied air to a degree that made long-distance shots very strenuous work for the eyes. Although our base signals were stone piles higher than a man, I was often forced to keep my eye to the telescope for hours to catch a glimpse of the signals; lack of time did not allow me to stop the telescope work in the hottest part of the day.

The top of Coropuna was intersected from the four stations: 16,344, 15,545, 16,168, and 16,664 feet elevation, the intersections giving a very small triangular error. The elevation of Mount Coropuna’s high peak as computed from these 4 stations is:

21,696 feet 21,746 " 21,714 " 21,657 " ------ Mean elevation 21,703 feet above sea level.

The elevation of Coropuna as derived from these four stations has thus a mean error of 18 feet (method of least squares) while the elevation of each of the four stations as carried up from mean sea level through 25 stations--vertical angles being observed in both directions--has an estimated mean error of 30 feet. The result of this is a mean error of 35 feet in Coropuna’s elevation above mean sea level.

The latitude is 15° 31′ 00″ S.; the longitude is 72° 42′ 40″ W. of Greenwich, the checking of these two determinations giving a result unexpectedly close.

On November 11th azimuth and latitude observations were taken at Chuquibamba and two days later we arrived at Aplao in the bottom of the splendid Majes Valley. In the northern part of this valley I was prevented from doing any plane-table work in the afternoons of four successive days. A strong gale set in each noon raising a regular sandstorm, that made seeing almost impossible, and blowing with such a velocity that it was impossible to set up the plane-table.

From Hacienda Cantas to Camaná we had to pass the western desert for a distance of 45 miles. We were told that on the entire distance there was only one camping place. This was at Jaguey de Majes, where there was a brook with just enough water for the animals but no fodder. Thus we faced the necessity of carrying water for ten men and fodder for 14 animals in excess of the usual cargo; and we were unable to foretell how many days the topography over the hot desert would require.

Although plane-table work in the desert was impossible at all except in the earliest and latest hours of the day, we made regular progress. We camped three nights at Jaguey and arrived on the fourth day at Las Lomas.

The next morning, on November 23rd, at an elevation of 2178 feet near the crest of the Coast Range, we were repaid for two months of laborious work by a glorious view of the Pacific Ocean and of the city of Camaná with her olive gardens in the midst of the desert sand.

The next day I observed latitude and azimuth at Camaná and in the night my companion and assistant Mr. Watkins and I returned across the desert to the railroad at Vitor.

CONCLUSIONS

The planned methods were followed very closely. In two cases only the plane-table had to be oriented by the magnetic needle, the backsights not being obtainable because of the impossibility of locating the last station, passing Indians having removed the signals.

In one case only the distance between two stations had to be determined by graphic triangulation exclusively, the base signals having been destroyed. Otherwise graphic triangulation was used as a check on distances.

Vertical angles were always measured in both directions with the exception of the above-mentioned cases.

Observations for azimuth were always taken to the sun before and after noon. The direction used in the azimuth observation was also taken with the prismatic compass. The mean of the magnetic declination thus found is: East 8° 30′ plus.

Observations for latitude were taken to the sun by the method of circum-meridian altitudes, except at the town of Vilcabamba where star observations were taken.

As a matter of course, observations to the sun are not so exact as star observations, especially in low latitudes where one can expect to observe the near zenith. However, working in high altitudes for long periods, moving camp every day and often arriving at camp 2 to 4 hours after sunset, I found it essential to have undisturbed rest at night. It was beyond my capacity to spend an hour or two of the night in finding the meridian and in making the observation. Furthermore, the astronomic observations were to check the topography mainly, the latter being the most exact method with the outfit at hand.

The following table contains the comparisons between the latitude stations as located on the map and by observation:

Map Observation Camaná Quadrangle S 16° 37′ 34″ 16° 37′ 34″[66] Coropuna, station 9,691S 15° 48′ 30″ (15° 51′ 44″) Cotahuasi, " 12,588S 15° 11′ 40″ 15° 12′ 30″ La Cumbre, " 16,852S 14° 28′ 10″ 14° 29′ 46″ Lambrama, " 8,341S 13° 43′ 18″ 13° 43′ 14″

The other observations, with the exception of the one on the Coropuna Quadrangle, check probably as well as can be expected with the small and light outfit which we used, and under the exceptionally hard conditions of work. The observation on the Coropuna Quadrangle just south of Chuquibamba is, however, too much out. An explanation for this is that the meridian zenith distance was 1° 23′ 12″ only (in this case the exact formula was used in computing). Of course, an error or an accumulation of errors might have been made in the distances taken by the micrometer-alidade, but the first cause of error mentioned is the more probable, and this is indicated also by the fact that the location on the top of Mount Coropuna checks closely with the one determined in an entirely independent way by the railroad engineers.

For the cross-section map from Abancay to Camaná, the following statistics are desirable:

Micrometer traverse and graphic triangulation, with contours, field scale 1:90,000.

Total time required, days 40.5 Average distance per days in miles 7.5 Average number of plane-table stations occupied per day 1.5 Average area per day in square miles 38. Located points per square mile 0.25 Approximate elevations in excess of above, per square mile 0.25 Highest station occupied, feet above sea level 17,675. Highest point located, feet above sea level 21,703.

APPENDIX B

FOSSIL DETERMINATIONS

A few fossil collections were gathered in order that age determinations might be made. With the following identifications I have included a few fossils (I and II) collected by W. R. Rumbold and put into my hands in 1907. The Silurian is from a Bolivian locality south of La Paz but in the great belt of shales, slates, and schists which forms one of the oldest sedimentary series in the Eastern Andes of Peru as well as Bolivia. While no fossils were found in this series in Peru the rocks are provisionally referred to the Silurian. Fossil-bearing Carboniferous overlies them but no other indication of their age was obtained save their general position in the belt of schists already mentioned. I am indebted to Professor Charles Schuchert of Yale University for the following determinations.

I. _Silurian_

San Roque Mine, southwest slope of Santa Vela Cruz, Canton Ichocu, Province Inquisivi, Bolivia.

Sent by William R. Rumbold in 1907.

_Climacograptus?_ _Pholidops trombetana_ Clarke? _Chonetes striatellus_ (Dalman). _Atrypa marginalis_ (Dalman)? _Cœlospira_ n. sp. _Ctenodonta_, 2 or more species. _Hyolithes._ _Klœdenia._ _Calymene?_ _Dalmanites_, a large species with a terminal tail spine. _Acidaspis._

These fossils indicate unmistakably Silurian and probably Middle Silurian. As all are from blue-black shales, brachiopods are the rarer fossils, while bivalves and trilobites are the common forms. The faunal aspect does not suggest relationship with that of Brazil as described by J. M. Clarke and not at all with that of North America. I believe this is the first time that Silurian fossils have been discovered in the high Andes.

II. LOWER DEVONIAN

Near north end of Lake Titicaca.

_Leptocœlia flabellites_ (Conrad), very common. _Atrypa reticularis_ (Linnæus)?

This is a part of the well-known and widely distributed Lower Devonian fauna of the southern hemisphere.

III. _Upper Carboniferous_

All of the Upper Carboniferous lots of fossils represent the well-known South American fauna first noted by d’Orbigny in 1842, and later added to by Orville Derby. The time represented is the equivalent of the Pennsylvanian of North America.

Huascatay between Pasaje and Huancarama.

Crinoidal limestone. Trepostomata Bryozoa. _Polypora._ Common. _Streptorhynchus hallianus_ Derby. Common. _Chonetes glaber_ Geinitz. Rare. _Productus humboldti_ d’Orb. Rare. " _cora_ d’Orb. Rare. " _chandlessii_ Derby. " sp. undet. Common. " sp. undet. " _Spirifer condor_ d’Orb. Common. _Hustedia mormoni_ (Marcou). Rare. _Seminula argentea_ (Shepard). "

Pampaconas, Pampaconas valley near Vilcabamba.

_Lophophyllum?_ _Rhombopora_, etc. _Productus._ _Camarophoria._ Common. _Spirifer condor_ d’Orb. _Hustedia mormoni_ (Marcou). _Euomphalus._ Large form.

Pongo de Mainique. Extreme eastern edge of Peruvian Cordillera.

_Lophophyllum._ _Productus chandlessii_ Derby. " _cora_ d’Orb. _Orthotetes correanus_ (Derby). _Spirifer condor_ d’Orb.

River bowlders and stones of Urubamba river, just beyond eastern edge of Cordillera at mouth of Ticumpinea river. (Detached and transported by stream action from the Upper Carboniferous at Pongo de Mainique.)

Mostly Trepostomata Bryozoa. Many _Productus_ spines. _Productus cora_ d’Orb. _Camarophoria_. Same as at Pampaconas. _Productus_ sp. undet.

Cotahuasi A.

_Lophophyllum._ _Productus peruvianus_ d’Orb. " sp. undet. _Camarophoria._ _Pugnax_ near _utah_ (Marcou). _Seminula argentea_ (Shepard)?

Cotahuasi B.

_Productus cora_ d’Orb. " near _semireticulatus_ (Martin).

IV. _Comanchian or Lower Cretaceous_

Near Chuquibambilla.

_Pecten_ near _quadricostatus_ Sowerby. Undet. bivalves and gastropods. The echinid _Laganum? colombianum_ d’Orb. A clypeasterid.

This Lower Cretaceous locality is evidently of the same horizon as that of Colombia illustrated by d’Orbigny in 1842 and described on pages 63-105.

APPENDIX C

KEY TO PLACE NAMES

Abancay, town, lat. 12° 35′, Figs. 20, 204.

Abra Tocate, pass, between Yavero and Urubamba valleys, leaving latter at Rosalina, (Fig. 8). _See also_ Fig. 55.

Anta, town, lat. 13° 30′, Fig. 20.

Antabamba, town, lat. 14° 20′, Figs. 20, 204.

Aplao, town, lat. 16°, Figs. 20, 204.

Apurimac, river, Fig. 20.

Arequipa, town, lat. 16° 30′, Fig. 66.

Arica, town, northern Chile, lat. 18° 30′.

Arma, river, tributary of Apurimac, lat. 13° 25′, (Fig. 20); tributary of Ocoña, lat. 15° 30′, (Fig. 20).

Arma, village, lat. 13° 15′, Fig. 20. _See also_ Fig. 140.

Auquibamba, hacienda, lat. 13° 40′, Fig. 204.

Callao, town, lat. 12°, Fig. 66.

Camaná, town, lat. 16° 40′, Figs. 20, 66, 204.

Camisea, river, tributary of Urubamba entering from right, lat. 11° 15′.

Camp 13, lat. 14° 30′.

Cantas, hacienda, lat. 16° 15′, Fig. 204.

Caraveli, town, lat. 16°, Fig. 66.

Catacaos, town, lat. 5° 30′, Fig. 66.

Caylloma, town and mines, lat. 15° 30′, Fig. 66.

Caypi, village, lat. 13° 45′.

Central Ranges, lat. 14°, Fig. 20. _See also_ Fig. 157.

Cerro Azul, town, lat. 13°, Fig. 66.

Chachani, mt., overlooking Arequipa, lat. 16° 30′, (Fig. 66).

Chaupimayu, river, tributary of Urubamba entering at Sahuayaco, _q.v._

Chili, river, tributary of Vitor River, lat. 16° 30′, (Fig. 66).

Chinche, hacienda, Urubamba Valley above Santa Ana, lat. 13°, (Fig. 20).

Chira, river, lat. 5°, Fig. 66.

Choclococha, lake, lat. 13° 30′, Figs. 66, 68.

Choqquequirau, ruins, canyon of Apurimac above junction of Pachachaca River, lat. 13° 25′, (Fig. 20).

Choquetira, village, lat. 13° 20′, Fig. 20. _See also_ Fig. 136.

Chosica, village, lat. 12°, Fig. 66.

Chuquibamba, town, lat. 15° 50′, Figs. 20, 204.

Chuquibambilla, village, lat. 14°, Figs. 20, 204.

Chuquito, pass, Cordillera Vilcapampa between Arma and Vilcabamba valleys, lat. 13° 10′, (Fig. 20). _See also_ Fig. 139.

Coast Range, Figs. 66, 204.

Cochabamba, city, Bolivia, lat. 17° 20′, long. 66° 20′.

Colorada, pampa, lat. 15° 30′, Fig. 204.

Colpani, village, lower end of Canyon of Torontoy (Urubamba River), lat. 13° 10′. _See_ Fig. 158.

Copacavana, village, Bolivia, lat. 16° 10′, long. 69° 10′.

Coribeni, river, lat. 12° 40′, Fig. 8.

Coropuna, mt., lat. 15° 30′, Figs. 20, 204.

Corralpata, village, Apurimac Valley near Incahuasi.

Cosos, village, lat. 16°, Fig. 204.

Cotabambas, town, Apurimac Valley, lat. 13° 45′, (Fig. 20).

Cotahuasi, town, lat. 15° 10′, Figs. 20, 204.

Cuzco, city, lat. 13° 30′, Fig. 20.

Echarati, hacienda, on the Urubamba River between Santa Ana and Rosalina, lat. 12° 40′. _See_ inset map, Fig. 8, _and also_ Fig. 54.

Huadquiña, hacienda, Urubamba River above junction with Vilcabamba, lat. 13° 10′, (Fig. 20). _See also_ Fig. 158.

Huadquirca, village, lat. 14° 15′, Figs. 20, 204.

Huaipo, lake, north of Anta, lat. 13° 25′, (Fig. 20).

Huambo, village, left bank Pachachaca River between Huancarama and Pasaje, lat. 13° 35′, (Fig. 20).

Huancarama, town, lat. 13° 40′, Fig. 20.

Huancarqui, village, lat. 16° 5′, Fig. 204.

Huascatay, village, left bank of Apurimac above Pasaje, lat. 13° 30′, (Fig. 20).

Huaynacotas, village, lat. 15° 10′, Fig. 204.

Huichihua, village, lat. 14° 10′, Fig. 204.

(Tablazo de) Ica, plateau, lat. 14°-15° 30′, Fig. 66.

Ica, town, lat. 14°, Figs. 66, 67.

Incahuasi, village, lat. 13° 20′, Fig. 20.

Iquique, town, northern Chile, lat. 20° 15′.

(Pampa de) Islay, south of Vitor River, (Fig. 66).

Jaguey, village, Pampa de Sihuas, _q.v._

La Joya, pampa, station on Mollendo-Puno R.R., 16° 40′, (Fig. 66).

Lambrama, village, lat. 12° 50′, Fig. 20.

Lima, city, lat. 12°, Fig. 66.

Machu Picchu, ruins, gorge of Torontoy, _q.v._, lat. 13° 10′.

Majes, river, Fig. 204.

Manugali, river, tributary of Urubamba entering from left above Puviriari River, lat. 12° 20′, (Fig. 8).

Maritime Cordillera, Fig. 204.

Matara, village, lat. 14° 20′, Fig. 204.

(El) Misti, mt., lat. 16° 30′, Fig. 66.

Mollendo, town, lat. 17°, Fig. 66.

Moquegua, town, lat. 17°, Fig. 66.

Morococha, mines, lat. 11° 45′, Fig. 66.

Mulanquiato, settlement, lat. 12° 10′, Fig. 8.

Occobamba, river, uniting with Yanatili, _q.v._

Ocoña, river, lat. 15°-16° 30′, Figs. 20, 66.

Ollantaytambo, village. Urubamba River below Urubamba town, lat. 13° 15′, (Fig. 20), _and see_ inset map, Fig. 8.

Pabellon, hacienda, Urubamba River above Rosalina, (Fig. 20). _See also_ Fig. 55.

Pacasmayo, town, lat. 7° 30′, Fig. 66.

Pachatusca (Pachatusun), mt., overlooking Cuzco to northeast, lat. 13° 30′.

Pachitea, river, tributary of Ucayali entering from left, lat. 8° 50′.

Paita, town, lat. 5°, Fig. 66.

Pampacolea, village, south of Coropuna, _q.v._

Pampaconas, river, known in lower course as Cosireni, tributary of Urubamba River, (Fig. 8). Source in Cordillera Vilcapampa west of Vilcabamba.

Pampas, river, tributary of Apurimac entering from left, lat. 13° 20′.

Panta, mt., Cordillera Vilcapampa, northwest of Arma, lat. 13° 15′, (Fig. 20). _See also_ Fig. 136.

Panticalla, pass, Urubamba Valley above Torontoy, lat. 13° 10′.

Pasaje, hacienda and ferry, lat. 13° 30′, Fig. 20.

Paucartambo (Yavero), river, _q.v._

Paucartambo, town, head of Paucartambo (Yavero) River, lat. 13° 20′, long. 71° 40′. Inset map, Fig. 8.

Pichu-Pichu, mt., overlooking Arequipa, lat. 16°, (Fig. 66).

Pilcopata, river, tributary of Upper Madre de Dios east of Paucartambo, lat. 13°.

Piñi-piñi, river, tributary of Upper Madre de Dios east of Paucartambo, lat. 13°.

Pisco, town, lat. 14°, Fig. 66.

Piura, river, lat. 5°-6°, Fig. 66.

Piura, town, lat. 5° 30′, Fig. 66.

Pomareni, river, lat. 12°, Fig. 8.

Pongo de Mainique, rapids, lat. 12°, Fig. 8.

Pucamoco, hacienda, Urubamba River, between Santa Ana and Rosalina, (Fig. 20).

Puquiura, village, lat. 13° 5′, Fig. 20. _See also_ Fig. 158. Distinguish Puqura in Anta basin near Cuzco.

Puqura, village, Anta basin, east of Anta, lat. 13° 30′, (Fig. 20).

Quilca, town, lat. 16° 40′, Fig. 66.

Quillagua, village, northern Chile, lat. 21° 30′, long. 69° 35′.

Rosalina, settlement, lat. 12° 35′, Fig. 8. _See also_ Fig. 20.

Sahuayaco, hacienda, Urubamba Valley above Rosalina, (Fig. 20). _See also_ Fig. 55.

Salamanca, town, lat. 15° 30′, Fig. 20.

Salaverry, town, lat. 8°, Fig. 66.

Salcantay, mt., lat. 13° 20′, Fig. 20.

San Miguel, bridge, canyon of Torontoy near Machu Picchu, lat. 13° 10′.

Santa Ana, hacienda, lat. 12° 50′, Fig. 20.

Santa Ana, river, name applied to the Urubamba in the region about hacienda Santa Ana.

Santa Lucia, mines, lat. 16°, Fig. 66.

Santo Anato, hacienda, La Sama’s hut, 12° 35′, Fig. 8.

Sihuas, Pampa de, lat. 16° 30′, Fig. 204.

Sillilica, Cordillera, east of Iquique, northern Chile.

Sintulini, rapids of Urubamba River above junction of Pomareni, lat. 12° 10′, (Fig. 8).

Sirialo, river, lat. 12° 40′, Fig. 8.

Soiroccocha, mt., Cordillera Vilcapampa north of Arma, lat. 13° 15′, (Fig. 20).

Solimana, mt., lat. 15° 20′, Fig. 204.

Soray, mt., Cordillera Vilcapampa, southeast of Mt. Salcantay, lat. 13° 20′, (Fig. 20).

Sotospampa, village, near Lambrama, lat. 13° 50′, (Fig. 204).

Sullana, town, Chira River, lat. 5°, (Fig. 66).

Taurisma, village, lat. 15° 10′, Fig. 204.

Ticumpinea, river, tributary of Urubamba entering from right below Pongo de Mainique, lat. 11° 50′, (Fig. 8).

Timpia, river, tributary of Urubamba entering from right, lat. 11° 45′.

Tono, river, tributary of Upper Madre de Dios, east of Paucartambo, lat. 13°.

Torontoy, canyon of the Urubamba between the villages of Torontoy and Colpani, lat. 13° 10′-13° 15′.

Torontoy, village at the head of the canyon of the same name, lat. 13° 15′. _See_ inset map, Fig. 8.

Tumbez, town, lat. 4° 30′, Fig. 66.

Tunari, Cerro de, mt., northwest of Cochabamba, _q.v._

Urubamba, river, Fig. 20.

Urubamba, town, lat. 13° 20′, Fig. 20.

Vilcabamba, river, tributary of Urubamba River entering from left above Santa Ana, lat. 13°, Fig. 8. _See also_ Fig. 158.

Vilcabamba, village, lat. 13° 5′, Fig. 20. _See also_ Fig. 158.

Vilcanota, Cordillera, southern Peru.

Vilcanota, river, name applied to Urubamba above lat. of Cuzco, 13° 30′, (Fig. 20).

Vilcapampa, Cordillera, lat. 13° 20′, Fig. 20.

Vilque, town, southern Peru, lat. 15° 50′, long. 70° 30′.

Vitor, pampa, lat. 16° 30′, Fig. 66.

Vitor, river, Fig. 66.

Yanahuara, pass, between Urubamba and Yanatili valleys, lat. 13° 10′.

Yanatili, river, tributary of Urubamba entering from right above Rosalina, (Fig. 20). _See also_ Fig. 65.

Yavero (Paucartambo), river, tributary of Urubamba entering from right, lat. 12° 10′, Fig. 8.

Yavero, settlement, at junction of Yavero and Urubamba rivers, lat. 12° 10′, Fig. 8.

Yunguyo, town, southern Peru, lat. 16° 20′, long. 69° 10′.

Yuyato, river, lat. 12° 5′, Fig. 8.

INDEX

Abancay, 32, 62, 64, 78, 92, 93, 181, 189, 221, 243; suppressing a revolution, 89-91; temperature curve (diagr.), opp. p. 180

Abancay basin, 154

Abancay to Camaná cross-section map, work, observation and statistics, 315

Abra Tocate, 73, 80, 81; topography and vegetation from (ill.), opp. p. 19

Abra de Malaga, 276

Acosta, 205

Adams, G. I., 255

Agriculture, 74-76, 152

Aguardiente, 74. _See_ Brandy

Alcohol, 5, 6

Alluvial fans, 60-63, 70, 270

Alluvial fill, 270-273; view in Majes Valley (ill.), opp. p. 230

Alpacas, 5, 52

Alto de los Huesos (ill.), opp. p. 7

Amazon basin, Humboldt’s dream of conquest, 33-35; Indian tribes, 36

Amazonia, 20, 26

Ancachs, 171

Andahuaylas, 89

Andrews, A, C., 295

Angulo, Philippi, 317

Anta, 187, 189, 190

Anta basin, 62, 108, 197; geology, 250; view looking north from hill near Anta (ill.), opp. p. 184

Antabamba, 52, 53, 95, 96, 99, 101, 189, 197, 243, 303, 316; Governor, 95-99, 100-101; Lieutenant Governor, 96-99, 101; sketch section, 243

Antabamba Canyon, view across (ill.), opp. p. 106

Antabamba Quadrangle, 316, opp. p. 282 (topog. sheet)

Antabamba region, geologic sketch map and section, 245

Antabamba Valley, 96

“Antis,” 39

Aplao, 106, 115, 116, 181, 226, 231, 255, 256, 257, 273, 318; composite structure section (diagr.), 259; temperature curve (diagr.), 181

Aplao Quadrangle (topog. sheet), opp. p. 120

Appendix A, 315

Appendix B, 321

Appendix C, 324

Apurimac, 51, 57, 60, 94, 153, 154; crossing at Pasaje (ills.), opp. p. 91; regional diagram of canyoned country, 58

Apurimac Canyon, 189; cloud belt (ill.), opp. p. 150

Arequipa, 52, 89, 92, 117, 120, 137, 284; glacial features near (sketches), 280

Argentina, 93

Arica, 130, 132, 198

Arma, 67, 189, 212-214

Arrieros, Pampa de, 280

Asymmetrical peaks (ill.), opp. p. 281

Asymmetry, 305-313; cross-section of ridge (diagr.), 306; postglacial volcano (diagr.), 306

Auquibamba, 93

Avalanches, 290

Bailey, S. I., 284

Bandits, 95

Basins, 60, 154; regional diagram, 61; climatic cross-section (diagr.), 62

Batholith, Vilcapampa, 215-224

Belaunde brothers, 116

Bergschrunds, 294-305

Bingham, Hiram, ix, 104, 157

Block diagram of physiography of Andes, 186

Boatmen, Indian, 13

Bogotá, Cordillera of, 205

Bolivia, 93, 176, 190, 193, 195, 240, 241, 249, 322; snowline, 275-277

Bolivian boundary, 68

Border valleys of the Eastern Andes, 68-87

Borneo, 206

Bowman, Isaiah, 8, 316

Brandy, 74, 75, 76, 82-83

Bravo, José, 245

Bumstead, A. H., ix

Cacao, 74, 83

Cacti, 150; arboreal (ill.), opp. p. 90

Calchaquí Valley, 250

Callao, 118; cloudiness (with diagr.), 133; temperature (with diagr.), 126-129; wind roses (diagrs.), 128

Camaná, 21, 112, 115, 116, 117, 118, 140-141, 147, 181, 225, 226, 227, 266, 318; coastal Tertiary, 253, 254; plain of, 229; temperature curve (diagr.), 181

Camaná Quadrangle (topog. sheet), opp. p. 114

Camaná Valley, 257

Camaná-Vitor region, 117

Camino del Peñon, 110

Camisea, 36

Camp 13, 100, 180, 181; temperature curve (diagr.), 180

Campas, 37

Canals for bringing water, 59, 60, 155; projected, Maritime Cordillera (diagr.), 118

Cantas, 115, 116, 226, 253, 257, 273, 318

Canyon walls (ills.), opp. p. 218

Canyoned country, regional diagram, 58; valley climates (diagr.), 59

Canyons, 60, 72, 73, 197, 219; Majes River (ill.), opp. p. 230; topographic conditions before formation of deep canyons in Maritime Cordillera (ill.), opp. p. 184

Caraveli, climate data, 134-136; wind roses (diagrs.), 136

Carboniferous fossils, 323

Carboniferous strata, 241-247; hypothetical distribution of land and sea (diagr.), 246

Cashibos, 37

Catacaos, 119

Cattle tracks (ill.), opp. p. 226

Caucho, 29

Caylloma, 164, 165

Caypi, 316

Central Ranges, asymmetrical peaks (ill.), opp. p. 281; glacial features with lateral moraines (ill.), opp. p. 269; glacial topography between Lambrama and Antabamba (ill.), opp. p. 280; steep cirque walls (ill.), opp. p. 286

Cerro Azul, 118

Cerro de Tunari, 176

Chachani, 280, 284

Chanchamayo, 77

Character. _See_ Human character

Chaupimayu Valley, 77

_Chicha_, 86

Chile, 130, 132, 193, 260

Chili River, 120

Chili Valley, opp. p. 7 (ill.), 117

Chimborazo, 281

Chinche, 271, 272

Chira River, depth diagram, 119, 120

Chirumbia, 12

Choclococha, Lake, 120

Chonta Campas, 37

Choqquequirau, 154

Choquetira, 66, 67, 211; bowldery fill below, 269; glacial features, 206-207

Choquetira Valley, moraine, (ill.), opp. p. 208

Chosica, 136, 137; cloudiness (diagr.), 138

_Chuño_, 57

Chuntaguirus, 41

Chuquibamba, 54, 72, 107, 110, 111, 112, 115, 116, 273, 317-319; sediments, 258

Chuquibambilla, 53, 189, 220, 221, 222, 236, 243; alluvial fill (diagr.), 272; Carboniferous, 244; fossils, 323

Chuquito pass, crossing (ill.), opp. p. 7; glacial trough (ill.), opp. p. 205

Cirque walls, steep (ill.), opp. p. 286

Cirques, 294-305; development (diagr.), 300; development, further stages (diagr.), 301; mode of formation (diagr.), 297

Clarke, J. M., 321

Clearing in forest (ill.), opp. p. 25

Climate, coast, 125-147; eastern border, 147-153; Inter-Andean valleys, 153-155; _see also_ Meteorological records

Climatic belts, 121-122; map, 123

Climatology, 121-156

Cliza, 276

Cloud-banners, 16

Cloud belt, 143, opp, p. 150 (ill.)

Cloudiness, 132; Callao (with diagr.), 133; desert station near Caraveli (diagrs.), 137; Machu Picchu, 160; Santa Lucia (diagr.), 169

Clouds, Inter-Andean Valley, 155; Santa Ana (ill.), opp. p. 180; Santa Lucia, 168; types on eastern border of Andes (diagrs.), 148; _see also_ Fog

Coast Range, 111, 113, 114, 116, 118, 225-232; climate, 122-147; direction, 267; diagram to show progressive lowering of saturation temperature in a desert, 127; geology, 258; view between Mollendo and Arequipa in June (ill.), opp. p. 226; wet and dry seasons (diagrs.), 132

Coastal belt, map of irrigated and irrigable land, 113

Coastal desert, 110-120; regional diagram of physical relations, 112; _see also_ Deserts

Coastal planter, 6

Coastal region, topographic and climatic provinces (diagr.), 125

Coastal terraces, 225-232

Coca, 74, 77, 82-83

Coca seed beds (ill.), opp. p. 74

Cochabamba, 93; temperature (diagrs. of ranges), insert opp. p. 178; weather data, 176-178

Cochabamba Indians, 276

Colombia, 205

Colorada, Pampa de, 114, 317

Colpani, 72, 215, 216, 222, 223; from ice to sugar cane (ill.), opp. p. 3

Comanchian fossils, 323

Cómas, 155

Compañia Gomera de Mainique, 29, 31, 32

Concession plan, 29

Conibos, 44

_Contador_, 84-85

Copacavana, 176

Cordilleras, 4, 6, 20, 197

Coribeni, 15

Corn, 57, 59, 62

Coropuna, 109, 110, 112, 202, 253, 317, 319; elevation, 317; glaciation, 307; snowline, 283-285

Coropuna expedition, 104

Coropuna Quadrangle, 197, opp. p. 188 (topog. sheet), 319

Corralpata, 51, 59

Cosos, 231

Cotabambas, 78

Cotahuasi, 4, 5, 52, 54, 60, 97, 101, 103, 104, 180, 197, 199, 316, 317; alluvial fill, 272; fossils, 322; geologic sketch maps and cross-section, 247; rug weaver (ill.), opp. p. 68; snowline above, 282-283; temperature curve (diagr.), 180; view (ill.), opp. p. 57

Cotahuasi Canyon, 247, 248, 316

Cotahuasi Quadrangle (topog. sheet), opp. p. 192

Cotahuasi Valley, geology, 258

Cotton, 76, 116, 117

Crest lines, asymmetrical, 305-313

Cretaceous formations, 247-251

Cretaceous fossils, 323

Crucero Alto, 188

Cuzco, 8, 10, 21, 52, 62, 63, 92, 102, 107, 193, 197; railroad to Santa Ana, 69-70; snow, 276; view (ill.), opp. p. 66

Cuzco basin, 61, 62, 154, 251; slopes at outlet (diagr.), 185

Deformations. _See_ Intrusions

Derby, Orville, 322

Desaguadero Valley, 193

Deserts, cloudiness (diagrs.), 137; rain, 138-140; sea-breeze in, 132; tropical forest, 36-37; wind roses (diagrs.), 136

Diagrams. _See_ Regional diagrams

Dikes, 223

Drunkenness, 103, 105-106, 108

Dry valleys, 114-115

Dunes, 114, 254; Majes Valley, 262-267; movement, 132; superimposed (diagrs.), 265

Duque, Señor, 78

Eastern Andes, 204-224; regional diagram, 22

Eastern border, climate, 147-153

Eastern valley planter, 3

Eastern valleys, 68-87; climate cross-section (diagr.), 79

Echarati, 10, 77, 78, 80, 82; plantation scene (ill.), opp. p. 75

Ecuador volcanoes, 281

Epiphyte (ill.), opp. p. 78

Erdis, E. C., 158

Erosion, 192-195, 210, 211, 305; _see also_ Glacial erosion; Nivation

Erving, Dr. W. G., 13, 101, 316, 317

_Faena_ Indians, 75, 83-87

Feasts and fairs, 175-176

Ferries, 147

Fig tree (ill.), opp. p. 75

Floods, 151

Fog, 132, 139, 143; conditions along coast from Camaná to Mollendo, 144-145; _see also_ Clouds

Forest dweller, 1

Forest Indians. _See_ Machigangas

Forests, clearing (ill.), opp. p. 25; dense ground cover, trees, epiphytes, and parasites (ill.), opp. p. 155; moss-draped trees (ill.), opp. p. 24; mountain, 148-153; mule trail (ill.), opp. p. 18; tropical, near Pabellon (ill.), opp. p. 150; tropical vegetation (ill.), opp. p. 18; type at Sahuayaco (ill.), opp. p. 90

Fossils, 245, 321; list of, by geologic periods and localities, 321

Frankland, 278, 309

Frost line, 56-57

Garua, 132

Geographical basis of revolutions and of human character, 88-109

Geologic dates, 195-196; Majes Valley, 258, 261; west coast fault, 248-249

Geologic development. _See_ Physiographic and geologic development

Gilbert, G. K., 300, 302, 305

Glacial deposits, 268

Glacial erosion, Central Andes, 305-313; composite sketch of general conditions, 312; graphic representation of amount during glacial period, 311

Glacial features, 274-313; Arequipa (sketches), 280; Central Ranges; lateral moraines (ill.), opp. p. 269; eastern slopes of Cordillera Vilcapampa (map), 210

Glacial retreat, 208-214

Glacial sculpture, heart of the Cordillera Vilcapampa (map), 212; southwestern flank of Cordillera Vilcapampa (map), 207

Glacial topography between Lambrama and Antabamba (ill.), opp. p. 280; Maritime Cordillera, north of divide on 73d meridian (ill.), opp. p. 281

Glacial trough, view near Chuquito pass (ill.), opp. p. 208

Glaciation, 64, 271; Sierra Nevada, 305; Vilcapampa, 204-214; Western Andes, 202

Glaciers, Panta Mountain (ill.), opp. p. 287; view (ill.), opp. p. 205

Gomara, 34

Gonzales, Señor, 78

Government, bad, 95

Gran Pajonal, 37

Granite, 215-224; _see also_ Intrusions

Grass (ill.), opp. p. 154

Gregory, J. W., 205

_Hacendado_, 55, 60

_Haciendas_, 78, 83, 86

Hann, J., 126, 176, 278

Hendriksen, Kai, 98, 315

Hettner, 205

Hevea, 29

Highest habitations in the world, 52, 96; regional diagram of, 50; stone hut (ill.), opp. p. 48

Highland shepherd, 4

Highlands, 46

Hobbs, W. H., 286, 287

Horses, 66, opp. p. 91 (ill.)

Huadquiña, 70, 71, 72, 75, 82, 86, 219; hacienda (ill.), opp. p. 73; terraces, 272

Huadquirca, 243

Huaipo, Lake, 250, 251

Huallaga basin, 153

Huambo, 243

Huancarama, 64, 87, 189, 243, 303; view (ill.), opp. p. 106

Huancarqui, 257

Huari, 176

Huascatay, 189, 242, 243; Carboniferous, 244; fossils, 322

Huasco basin, 275

Huaynacotas, 103, 316; terraced valley slope (ill.), opp. p. 56; terraced valley slopes (ill.), opp. p. 199

Huichihua, 278; alluvial fill (diagr.), 272; (ill.), opp. p. 67

Human character, geographic basis, 88-109

Humboldt, 33-35, 286

Humboldt Current, 126, 143

Huts, 103; highest in Peru (ill.), opp. p. 48; shepherds’, 47, 48, 52, 55

Ica Valley, 120; irrigated and irrigable land (diagr.), 118

Ice erosion. _See_ Glacial erosion

Incahuasi, 51, 155, 285

Incas, 39, 44, 46, 62, 63, 68, 77, 109, 175

Incharate, 78

Indian boatmen, 13

Indians, as laborers, 26-28, 31-32; basin type, 63-64; forest, _see_ Machigangas; life and tastes, 107-108; mountain, 46-67, 101-102; plateau, 40-41, 44-45, 100, 106-109; troops, 90, 91; wrongs, 14, 102

Ingomwimbi, 206

Instruments, surveying, 315

Inter-Andean valleys, climate, 153-155

Intermont basin. _See_ Basins

Intrusions, deformations north of Lambrama (diagr.), 243; deformative effects on limestone strata near Chuquibambilla (diagr.), 221; lower Urubamba Valley (geologic sketch map), 237; overthrust folds in detail near Chuquibambilla (diagr.), 222; principles, 217-219

Intrusions, Vilcapampa, deformative effects near Puquiura (diagr.), 216; relation of granite to schist near Colpani (with diagr.), 216

Iquique, wind roses (diagrs.), 131

Irrigation, 72, 76, 80, 82; coastal belt (map), 113; coastal desert, 119-120; Ica Valley (diagr.), 118

Islay, Pampa de, 114

Italians, 18, 81

Jaguey, 254, 255, 318

Jesuits, 68

Johnson, W. D., 213, 295, 296, 299, 300

Kenia, Mt., 206, 274

Kerbey, Major, 8, 10

Kibo, 206, 274

Kilimandjaro, 205, 206

Kinibalu, 206

Krüger, Herr, 157

Labor, 26-28, 31-32, 42-43, 74-75, 83-84

La Cumbre Quadrangle, 197, 202, opp. p. 202 (topog. sheet)

La Joya, 132, 133; cloudiness (diagr.), 134; temperature curves (diagr.), 134; wind roses (diagrs.), 135

Lambrama, 90, 92, 285, 316; camp near (ill.), opp. p. 6

Lambrama Quadrangle (topog. sheet), opp. p. 304

Lambrama Valley, deformation types (diagr.), 243

Land and sea, Carboniferous hypothetical distribution compared with present (diagr.), 246

Landscape, 183-198

Lanius, P. B., 13

La Paz, 93, 109, 276, 321

La Sama, 12, 13, 40

Las Lomas, 318

Lava flows, 199

Lava plateau, 197, 199, 307-308; regional diagram of physical conditions, 55; summit above Cotahuasi (ill.), opp, p. 204

Lavas, volume, 201

Lima, 92, 93, 118, 137, 138; cloud, 132, 143; temperature, 126

Limestone, sketch to show deformed, 243

Little, J. P., 135, 157

Llica, 275

Lower Cretaceous fossils, 323

Lower Devonian fossils, 321

Machigangas, 10, 11, 12, 14, 18, 19, 31, 36-45, 81; ornaments and fabrics (ill.), opp. p. 27; trading with (ill.), opp. p. 26

Machu Picchu, 72, 220; weather data (with diagr.), 158-160

Madeira-Mamoré railroad, 33

Madre de Dios, 1, 2, 33

Majes River, 147, 225, 227, 266, 267; Canyon (ill.), opp. p. 230

Majes Valley, 106, 111, 116, 117, 120, 226, 227, 229-231, 318; alluvial fill, 273; date of formation, 258, 261; desert coast (ill.), opp. p. 110; dunes, 262-267; erosion and uplift, 261; lower and upper sandstones (ill.), opp. p. 250; sediments, 255; snowline, 283; steep walls and alluvial fill (ill.), opp. p. 230; structural details near Aplao (sketch section), 255; structural details on south wall near Cantas (sketch section), 257; structural relations at Aplao (field sketch), 256; Tertiary deposits, 253-254; wind, 130; view below Cantas (ill.), opp. p. 110; view down canyon (ill.), opp. p. 144

Malaria, 14, 38

Marañon, 41, 59

Marcoy, 79

Marine terrace at Mollendo (ill.), opp. p. 226

Maritime Cordillera, 52, 199-203, 233; asymmetry of ridges, 308-309; glacial features, 307; glacial topography north of divide on 73d meridian (ill.), opp. p. 281; pre-volcanic topography, 200; post-glacial volcano, asymmetrical (diagr.), 306; regional diagrams, 50, 52; test of explanation of cirques, 303; volcanoes, tuffs, lava flows (ill.), opp. p. 204; western border rocks (geologic section), 257; _see also_ Lava plateau

Matara, 99, 316

Matthes, F. E., 286, 287, 289

Mature slopes, 185-193; between Ollantaytambo and Urubamba (ill.), opp. p. 185; dissected, north of Anta (ill.), opp. p. 185

Mawenzi, 206

Meanders, 16, 17

Médanos, 114

Mendoza, Padre, 11

Mer de Glace, 203

Meteorological records, 157-181

Mexican revolutions, 93

Middendorf, 143

Miller, General, 41, 78, 147

Minchin, 241

Misti, El, opp. p. 7 (ill.), 284

Molina, Christoval de, 175

Mollendo, 93, 105, 117; cloud belt, 143; cloudiness (diagr.), 134; coastal terraces, 225; humidity, 133; marine terrace (ill.), opp. p. 226; profile of coastal terraces (diagr.), 227; temperature curves (diagr.), 134; wind roses (diagrs.), 129

Mollendo-Arequipa railroad, 117

Mollendo rubber, 32

Montaña, 148, 149, 153

Moquegua, 117; geologic relations (diagr.), 255

Moraines, 207, 210-211; Choquetira Valley (ill.), opp. p. 208; view (ill.), opp. p. 208

Morales, Señor, 11

Morococha, temperature (diagrs. of ranges), insert opp. p. 172; weather data (with diagrs.), 171-176

Morococha Mining Co., 157, 171

Morro de Arica, 132

Moss, large ground. _See Yareta_

Moss-draped trees (ill.), opp. p. 24

Mountain-side trail (ill.), opp. p. 78

Mountains, tropical, as climate registers, 206

Mulanquiato, 10, 18, 19

Mule trail (ill.), opp. p. 18

Mules, 23, 24, 94, opp. p. 91 (ill.)

Névé, 286-305

Niño, El, 137-138

Nivation, 285-294; “pocked” surface (ill.), opp. p. 286

Northeastern border, topographic and structural section (diagr.), 241

Occobamba Valley, 79

Ocean currents of adjacent waters, 121-122 (map), 123

Ollantaytambo, 70, 73, 75, 250, 271; terraced valley floor (ill.), opp. p. 56

d’Orbigny, 322

Oruro, 93

Pabellon, 80, 82, opp. p. 150

Pacasmayo, Carboniferous land plants, 245

Pachitea, 37, 38

Pacific Ocean basin, 248

Paleozoic strata (ill.), opp. p. 198

_Palma carmona_, 29

Palmer, H. S., 250

Paltaybamba, opp. p. 74

Pampacolca, 109

Pampaconas, 69, 211, 213, 215; rounded slopes near Vilcabamba (ill.), opp. p. 72; Carboniferous, 244; fossils, 322; snow action, 291

Pampaconas River, 316

Pampas, 114, 198; climate data, 134-136

Pampas, river, 189

Panta, mt., 214; view, with glacier system (ill.), opp. p. 287

Pará rubber, 32

Pasaje, 51, 57, 59, 60, 236, 238, 240, 241, 243; Carboniferous, 244; crossing the Apurimac (ills.), opp. p. 91

Paschinger, 274

Pastures, 141, 187; Alpine (ill.), opp. p. 58

Paucartambo, 42, 77

Paucartambo River. _See_ Yavero River

Payta, 225

Penck, A., 205

Peonage, 25, 27, 28

Pereira, Señor, 10, 18

Perene, 155

Physiographic and geologic development, 233-273

Physiographic evidence, value, 193-195

Physiographic principles, 217

Physiography, 183-186; Southern Peru, summary, 197-198

Pichu-Pichu, 284

Piedmont accumulations, 260

Pilcopata, 36

Piñi-piñi, 36

Pisco, 130; Carboniferous land plants, 247

Piura, 119

Piura River, depth diagram, 119, 120

Piura Valley, 48

Place names, key to, 324

Plantations, 86; _see also_ Haciendas

Planter, coastal, 6

Planters, valley, 3, 75, 76

Plateau Indians, 40-41, 44-45, 100, 106-109

Plateaus, 196-197

Pleistocene deposits, 267-273

Pomareni, 19

Pongo de Mainique, 8, 9, 11, 15-20, 40, 71, 179, 239, 241, 242, 273; canoe in rapid above (ill.), opp. p. 11; Carboniferous, 244; dugout in rapids below (ill.), opp. p. 2; fossils, 322; temperature curve (diagr.), 178; upper entrance (ill.), opp. p. 10; vegetation, clearing, and rubber station (ill.), opp. p. 2

Poopó, 195

Potato field (ill.), opp p. 67

Potatoes, 57, 59, 62

Potosí, 249

Precipitation. _See_ Rain

Profiles, composition of slopes and profiles (diagr.), 191

Pucamoco, 78

Pucapacures, 42

Puerto Mainique, 29, 30

Punas, 6, 197

Puquiura, 67, 87, 211, 216, 236, 238, 239, 243, 277; Carboniferous, 244; composition of slopes (ill.), opp. p. 198

Puqura, 250

Quebradas, 145, 155

Quechuas, 44, 45, 77, 83

_Quenigo_, 285

Quilca, 105, 117, 226, 266

Quillabamba, opp. p. 74

Quillagua, 260

Railroads, 74, 75, 76, 93, 101-102, 149; Bolivia, 93; Cuzco to Santa Ana, 69-70

Raimondi, 77, 78, 109, 110, 135, 155, 170, 316

Rain, 115, 119, 120, 122, 124-125; coast region seasonal variation, 131-137; eastern border of Andes, belts (diagrs.), 148; effect of heavy, 138-140; effect of sea-breeze, 131-132; heaviest, 147-148; Morococha (with diagrs.), 173-176; periodic variations, 137; Santa Lucia (with diagrs.), 164-166; unequal distribution in western Peru, 145-147

Regional diagrams, 50; index map, 23; note on, 51

Regions of Peru, 1, 7

Reiss, 205, 208

Revolutions, geographic basis, 88-109

Rhone glacier, 205

Rice, 76

Robledo, L. M., 9, 30, opp. p. 78

Rock belts, outline sketch along 73d meridian, 235

Rocks, Maritime Cordillera, pampas and Coast Range structural relations (sketch section), 254; Maritime Cordillera, western border (geologic section), 257; Moquegua, structural relations (diagr.), 255; Urubamba Valley, succession (diagr.), 249

Rosalina, 8, 9, 10, 11, 37, 42, 71, 73, 80, 82, 153, 237

Rubber, 18; price, 32, 33

Rubber forests, 22-35

Rubber gatherers, Italian, 18, 81

Rubber plant (ill.), opp. p. 75

Rubber trees, 152

Rueda, José, 78

Rug weaver (ill.), opp. p. 68

Rumbold, W. R., 321

Russell, I. C., 205

Ruwenzori, 206, 274

Sacramento, Pampa del, 37

Sahuayaco, 77, 78, 80, 83, 179; forests (ills.), opp. p. 90; temperature curve (diagr.), 178

Salamanca, 54, 56, 105, 106, 180, 181; forest, 285; temperature curve (diagr.), 180; terraced hill slopes (ill.), opp. p. 58; view (ill.), opp. p. 107

Salaverry, 119

Salcantay, 64, 72, opp. p. 3 (ill.)

San Geronimo, 276

Sand. _See_ Dunes

“Sandy matico” (ill.), opp. p. 90

San Gabriel, Hacienda, 316

Santa Ana, 69, 72, 78, 79, 80, 82, 93, 153, 179, 237; clouds (ill.), opp. p. 180; temperature curve (diagr.), 178

Santa Ana Valley, 10, 82

Santa Lucia, temperature ranges (diagrs.), insert opp. p. 162; unusual weather conditions, 169-170; weather data (with diagrs.), 161-171

Santo Anato, 40, 42, 82, 179; temperature curve (diagr.), 178

Schists and Silurian slates, 236-241

Schrund. _See_ Bergschrunds

Schrundline, 300-305

Schuchert, Chas., 321

Sea and land. _See_ Land and sea

Sea-breeze, 129-132

Shepherd, highland, 4

Shepherds, country of, 46-67

Shirineiri, 36, 38

Sierra Nevada, 305

Sierra Nevada de Santa Marta, 205

Sievers, W., 143, 176, 205, 263

Sihuas, Pampa de, 114, 198

Sillilica, Cordillera, 190, 260

Sillilica Pass, 275

Silurian fossils, 321

Silurian slates, 236-241

Sintulini rapids, 19

Sirialo, 8, 15

Slave raiders, 14

Slavery, 24, 25

Slopes, composition at Puquiura (ill.), opp. p. 198; composition of slopes and profiles (diagr.), 191; smooth grassy (ill.), opp. p. 79; _see also_ Mature slopes

Smallpox, 14, 38

Snow, 212; drifting, 278; fields on summit of Cordillera Vilcapampa (ill.), opp. p. 268

Snow erosion. _See_ Nivation

Snow motion, curve of (diagr.), 293; law of variation, 291

Snowline, 52, 53, 66, 122, 148, 203, 205-206, 274-285; canting (with diagr.), 279; determination, 282; difference in degree of canting (diagr.), 281; glacial period, 282; view of canted, Cordillera Vilcapampa (ill.), opp. p. 280

Snowstorm, 170

Soiroccocha, 64, 72, 214; view (ill.), opp. p. 154

Solimana, 4, 202, 317; glaciation, 307

Soray, 64

Sotospampa, 243

South Pacific Ocean, 125

Spanish Conquest, 62, 63, 77

Spruce (botanist), 153

Steinmann, 249, 276

Streams, Coast Range, 145-147; physiography, 192; _see also_ Water

Structure. _See_ Rocks

Stübel, 209

Sucre, 93

Sugar, 73, 74, 75, 76, 82-83, 92

Sullana, 119

Survey methods employed in topographic sheets, 315

Tablazo de Ica, 198

Tarai. _See_ Urubamba Valley

Tarapacá, Desert of, 260

Tarapoto, 153

Taurisma, 317; geologic sketch map and cross-section, 248

Taylor, Capt. A., 126, 128

Temperature, Abancay curve (diagr.), opp. p. 180; Callao (with diagr.), 126-129; Cochabamba, 176-178; Cochabamba (diagrs. of ranges), insert opp. p. 178; curves at various points along 73d meridian, 178-181; La Joya curves (diagr.), 134; Mollendo curves (diagr.), 134; Morococha, 171-173; Morococha (diagrs. of ranges), insert opp. p. 172; progressive lowering of saturation, in a desert (diagr.), 127; Santa Lucia, 161-164; Santa Lucia (diagrs. of ranges), insert opp. p. 162

Tempests, 169-170

Terraces, coastal, 225-232; physical history and physiographic development (with diagrs.), 228-230; profile at Mollendo (diagr.), 227

Terraces, hill slopes (ill.), opp. p. 58

Terraces, marine (ill.), opp. p. 226

Terraces, valley (ills.), opp. p. 56, opp. p. 57, opp. p. 66; Huaynacotas (ill.), opp. p. 199

_Terral_, 130

Tertiary deposits, 249, 251-267; coastal, 253

Ticumpinea, 36, 38, 251

Tierra blanca, 254, 266

Timber line, 69, 71, 79, 148

Timpia, 36, 38, 252; canoe at mouth (ill.), opp. p. 19

Titicaca, 161, 176, 195, 321

Titicaca basin, 107

Titicaca-Poopó basin, 251

Tocate. _See_ Abra Tocate

_Tola_ bush (ill.), opp. p. 6

Tono, 36

Topographic and climatic cross-section (diagr.), opp. p. 144

Topographic and structural section of northeastern border of Andes (diagr.), 241

Topographic map of the Andes between Abancay and the Pacific Coast at Camaná, insert opp. p. 312

Topographic profiles across typical valleys (diagrs.), 189

Topographic regions, 121-122; map, 123

Topographic sheets, survey method employed, 315; list of, with page references, xi

Topographical outfit, 315

Torontoy, 10, 70, 71, 72, 82, 158, 220

Torontoy Canyon, 272, opp. p. 3 (ill.); cliff (ill.), opp. p. 10

Trail (mountain-side) (ill.), opp. p. 78

Transportation, 73-74, 93, 152; rains and, 142

Trees, 150; _see also_ Forests

_Tucapelle_ (ship), 117

Tucker, H. L., ix

Tumbez, 119

Tunari peaks, 276

Ucayali, 42, 44

Uplift, recent, 190

Upper Carboniferous fossils, 322

Urubamba, 1, 41, 42, 62, 187; village, 70, 73

Urubamba River, 72; fossils, 322; physiographic observations, 252-253; rapids and canyons, 8-21; shelter hut (ill.), opp. p. 11

Urubamba Valley, 72, 153, 238; alluvial fans, 270; alluvial fill, 272-273; below Paltaybamba (ill.), opp. p. 74; canyon walls (ill.), opp. p. 218; dissected alluvial fans (sketch), 271; floor from Tarai (ill.), opp. p. 70; from ice to sugar cane (ill.), opp. p. 3; geologic sketch map of the lower, 237; line of unconformity of geologic structure (ill.), opp. p. 250; rocks, 250; rocks, succession (diagr.), 249; sketch map, 9; slopes and alluvial deposits between Ollantaytambo and Torontoy (ill.), opp. p. 269; temperature curves (diagrs.), 178-179; terraced valley slopes and floor (ill.), opp. p. 66; vegetation, distribution (ill.), opp. p. 79; view below Santa Ana (ill.), opp. p. 155; wheat and bread, 71

Valdivia, Señor, 161

Vallenar, 49

Valley climates in canyoned region (diagr.), 59

Valley planters. _See_ Planters

Valley profiles, abnormal, 305-313

Valleys, eastern; _see_ Border valleys of the Eastern Andes; _see also_ Dry valleys, Inter-Andean valleys; topographic profiles across, typical in Southern Peru (diagrs.), 189

Vegetation, 141; belts (map), 123; distribution in Urubamba Valley (ill.), opp. p. 79; shrubbery, mixed with grass (ill.), opp. p. 154; Tocate pass (ill.), opp. p. 19; _see also_ Forests

Vicuña, 54

Vilcabamba, 66; rounded slopes (ill.), opp. p. 72

Vilcabamba pueblo, 211, 277, 296

Vilcabamba Valley, 189

Vilcanota knot, 276

Vilcanota Valley, alluvial fill, 272

Vilcapampa, Cordillera, 15, 16, 22, 51, 53, 64, 66, 67, 197, 204-224, 233; batholith and topographic effects, 215-224; canted snowline (ill.), opp. p. 280; climatic barrier, 73; composite geologic section (diagr.), 215; glacial features, 204-214; glaciers, 304; highest pass, crossing (ill.), opp. p. 7; regional diagram, 65; regional diagram of the eastern aspect, 68; schrundline, 302; snow movement, 287-289; snow fields on summit (ill.), opp. p. 268; snow peaks (ill.), opp. p. 72; snowline, 277, 279; southwestern aspect (ill.), opp. p. 205; summit view (ill.), opp. p. 205

Vilcapampa Province, 77

Vilcapampa Valley, bowldery fill, 269

Vilque, 176

Violle, 309

_Virazon_, 130

Vitor, Pampa de, 114, 318

Vitor River, 92, 117, 226, 266, 267

Volcanic country, 199

Volcanic flows, geologic sketch, 244

Volcanoes, glacial erosion, 311; post-glacial, 306-307; recessed southern slopes (ill.), opp. p. 287; snowline, 281; typical form, 310; views (ills.), opp. p. 204

Von Boeck, 176

Vulcanism, 199; _see also_ Volcanoes

Ward, R. De C., 126, 143

Water, 59, 60, 116, 139; projected canal from Atlantic to Pacific slope of the Maritime Cordillera (diagr.), 118; streams of coastal desert, intermittent and perennial, diagrams of depth, 119

Water skippers, 17

Watkins, Mr., 317, 318

Weather. _See_ Meteorological records

Western Andes, 199-203

Whymper, 205

Wind belts, 122; map, 123

Wind roses, Callao (diagrs.), 128; Caraveli (diagrs.), 136; Iquique (diagrs.), 131; La Joya (diagrs.), 135; Machu Picchu (diagrs.), 159; Mollendo (diagrs.), 129; Santa Lucia (diagrs.), 167; summer and winter of 1911-1913 (diagrs.), 130

Winds, 114, 116; directions at Machu Picchu, 158-159; geologic action, 262-267; prevailing, 125; Santa Lucia (with diagrs.), 166-168; trade, 122, 124; sea-breeze, 129-132

Wine, 116, 117

Wolf, 205

Yanahuara pass, 170

Yanatili, 41, 42, 44; slopes at junction with Urubamba River (ill.), opp. p. 79

_Yareta_ (ill.), opp. p. 6

Yavero, 30, 31, 36, 38, 42, 179; temperature curve (diagr.), 178

Yavero (Paucartambo) River, rubber station (ill.), opp. p. 24

Yuca, growing (ill.), opp. p. 75

Yunguyo, 176

Yuyato, 36, 38

* * * * *

FOOTNOTES:

[1] For all locations mentioned see maps accompanying the text or Appendix C.

[2] The Cashibos of the Pachitea are the tribe for whom the Piros besought Herndon to produce “some great and infectious disease” which could be carried up the river and let loose amongst them (Herndon, Exploration of the Valley of the Amazon, Washington. 1854, Vol. 1, p. 196). This would-be artfulness suggests itself as something of a match against the cunning of the Cashibos whom rumor reports to imitate the sounds of the forest animals with such skill as to betray into their hands the hunters of other tribes (see von Tschudi, Travels in Peru During the Years 1838-1842, translated from the German by Thomasina Ross, New York, 1849, p. 404).

[3] The early chronicles contain several references to Antisuyu and the Antis. Garcilaso de la Vega’s description of the Inca conquests in Antisuyu are well known (Royal Commentaries of the Yncas, Book 4, Chapters 16 and 17, Hakluyt Soc. Publs., 1st Ser., No. 41, 1869 and Book 7, Chapters 13 and 14, No. 45, 1871). Salcamayhua who also chronicles these conquests relates a legend concerning the tribute payers of the eastern valleys. On one occasion, he says, three hundred Antis came laden with gold from Opatari. Their arrival at Cuzco was coincident with a killing frost that ruined all the crops of the basin whence the three hundred fortunates were ordered with their gold to the top of the high hill of Pachatucsa (Pachatusun) and there buried with it (An Account of the Antiquities of Peru, Hakluyt Soc. Publs., 1st Ser., No. 48, 1873).

[4] Notice of a Journey to the Northward and also to the Northeastward of Cuzco. Royal Geog. Soc. Journ., Vol. 6, 1836, pp. 174-186.

[5] Walle states (Le Pérou Economique, Paris, 1907, p. 297) that the Conibos, a tribe of the Ucayali, make annual _correrias_ or raids during the months of July, August, and September, that is during the season of low water. Over seven hundred canoes are said to participate and the captives secured are sold to rubber exploiters, who, indeed, frequently aid in the organization of the raids.

[6] Distances are not taken from the map but from the trail.

[7] Compare with Raimondi’s description of Quiches on the left bank of the Marañon at an elevation of 9,885 feet (3,013 m.): “the few small springs scarcely suffice for the little patches of alfalfa and other sowings have to depend on the precarious rains.... Every drop of water is carefully guarded and from each spring a series of well-like basins descending in staircase fashion make the most of the scant supply.” (El Departamento de Ancachs, Lima, 1873.)

[8] Daily Cons. and Trade Report, June 10, 1914, No. 135, and Commerce Reports, March 20, 1916, No. 66.

[9] Reference to the figures in this chapter will show great variation in the level of the timber line depending upon insolation as controlled by slope exposure and upon moisture directly as controlled largely by exposure to winds. In some places these controls counteract each other; in other places they promote each other’s effects. The topographic and climatic cross-sections and regional diagrams elsewhere in this book also emphasize the patchiness of much of the woodland and scrub, some noteworthy examples occurring in the chapter on the Eastern Andes. Two of the most remarkable cases are the patch of woodland at 14,500 feet (4,420 m.) just under the hanging glacier of Soiroccocha, and the other the quenigo scrub on the lava plateau above Chuquibamba at 13,000 feet (3,960 m.). The strong compression of climatic zones in the Urubamba Valley below Santa Ana brings into sharp contrast the grassy ridge slopes facing the sun and the forested slopes that have a high proportion of shade. Fig. 54 represents the general distribution but the details are far more complicated. See also Figs. 53A and 53B. (See Coropuna Quadrangle.)

[10] Commenting on the excellence of the cacao of the montaña of the Urubamba von Tschudi remarked (op. cit., p. 37) that the long land transport prevented its use in Lima where the product on the market is that imported from Guayaquil.

[11] The inadequacy of the labor supply was a serious obstacle in the early days as well as now. In the documents pertaining to the “Obispados y Audiencia del Cuzco” (Vol. 11, p. 349 of the “Juicio de Limites entre el Perú y Bolivia, Prueba Peruana presentada al Gobierno de la República Argentina por Victor M. Maurtua,” Barcelona, 1900) we find the report that the natives of the curacy of Ollantaytambo who came down from the hills to Huadquiña to hear mass were detained and compelled to give a day’s service on the valley plantations under pain of chastisement.

[12] The Spanish occupation of the eastern valleys was early and extensive. Immediately after the capture of the young Inca Tupac Amaru and the final subjugation of the province of Vilcapampa colonists started the cultivation of coca and cane. Development of the main Urubamba Valley and tributary valleys proceeded at a good rate: so also did their troubles. Baltasar de Ocampo writing in 1610 (Account of the Province of Vilcapampa, Hakluyt Soc. Publs., Ser. 2, Vol. 22, 1907, pp. 203-247) relates the occurrence of a general uprising of the negroes employed on the sugar plantations of the region. But the peace and prosperity of every place on the eastern frontier was unstable and quite generally the later eighteenth and earlier nineteenth centuries saw a retreat of the border of civilization. The native rebellion of the mid-eighteenth century in the montaña of Chanchamayo caused entire abandonment of a previously flourishing area. When Raimondi wrote in 1885 (La Montaña de Chanchamayo, Lima, 1885) some of the ancient hacienda sites were still occupied by savages. In the Paucartambo valleys, settlement began by the end of the sixteenth century and at the beginning of the nineteenth before their complete desolation by the savages they were highly prosperous. Paucartambo town, itself, once important for its commerce in coca is now in a sadly decadent condition.

[13] Notice of a Journey to the Northward and also to the Eastward of Cuzco, and among the Chunchos Indians, in July, 1835. Journ. Royal Geog. Soc., Vol. 6, 1836, pp. 174-186.

[14] Bol. Soc. Geog. de Lima, Vol. 8, 1898, p. 45.

[15] Marcoy who traveled in Peru in the middle of the last century was greatly impressed by the sympathetic changes of aspect and topography and vegetation in the eastern valleys. He thus describes a sudden change of scene in the Occobamba valley: “... the trees had disappeared, the birds had taken wing, and great sandy spaces, covered with the latest deposits of the river, alternated with stretches of yellow grass and masses of rock half-buried in the ground.” (Travels in South America, translated by Elihu Rich, 2 vols. New York, 1875, Vol. 1, p. 326.)

[16] According to the latest information (August, 1916) of the Bolivia Railway Co., trains are running from Oruro to Buen Retiro, 35 km. from Cochabamba. Thence connection with Cochabamba is made by a tram-line operated by the Electric Light and Power Co. of that city. The Bulletin of the Pan-American Union for July, 1916, also reports the proposed introduction of an automobile service for conveyance of freight and passengers.

[17] During his travels Raimondi collected many instances of the isolation and conservatism of the plateau Indian: thus there is the village of Pampacolca near Coropuna, whose inhabitants until recently carried their idols of clay to the slopes of the great white mountain and worshiped them there with the ritual of Inca days (El Perú, Lima, 1874, Vol. 1).

[18] Raimondi (op. cit., p. 109) has a characteristic description of the “Camino del Peñon” in the department of La Libertad: “... the ground seems to disappear from one’s feet; one is standing on an elevated balcony looking down more than 6,000 feet to the valley ... the road which descends the steep scarp is a masterpiece.”

[19] Figs. 67 and 68 are from Bol. de Minas del Perú, 1906, No. 37, pp. 82 and 84 respectively.

[20] The Boletín de Minas del Peru, No. 34, 1905, contains a graphic representation of the régime of the Rio Chili at Arequipa for the years 1901-1905.

[21] Hann (Handbook of Climatology, translated by R. De C. Ward, New York, 1903) indicates a contributory cause in the upwelling of cold water along the coast caused by the steady westerly drift of the equatorial current.

[22] This is the elevation obtained by the Peruvian Expedition. Raimondi’s figure (1,832 m.) is higher.

[23] According to Ward’s observations the base of the cloud belt averages between 2,000 and 3,000 feet above sea level (Climatic Notes Made During a Voyage Around South America, Journ. of School Geogr., Vol. 2, 1898). On the south Peruvian coast, specifically at Mollendo, Middendorf found the cloud belt beginning about 1,000 feet and extending upwards to elevations of 3,000 to 4,000 feet. At Lima the clouds descend to lower levels (El Clima de Lima, Bol. Soc. Geogr. de Lima, Vol. 15, 1904). In the third edition of his Süd und Mittelamerika (Leipzig and Vienna, 1914) Sievers says that at Lima in the winter the cloud on the coast does not exceed an elevation of 450 m. (1,500 feet) while on the hills it lies at elevations between 300 and 700 m. (1,000 and 2,300 feet).

[24] In most of the coast towns the ford or ferry is an important institution and the _chimbadores_ or _baleadores_ as they are called are expert at their trade: they know the régime of the rivers to a nicety. Several settlements owe their origin to the exigencies of transportation, permanent and periodic; thus before the development of its irrigation system Camaná, according to General Miller (Memoirs, London, 1829, Vol. 2, p. 27), was a hamlet of some 30 people who gained their livelihood through ferrying freight and passengers across the Majes River.

[25] A dry pocket in the Huallaga basin between 6° and 7° S. is described by Spruce (Notes of a Botanist on the Amazon and Andes, 2 vols., London, 1908). Tarapoto at an elevation of 1,500 feet above sea level, encircled by hills rising 2,000 to 3,000 feet higher, rarely experiences heavy rain though rain falls frequently on the hills.

[26] Speaking of Cómas situated at the headwaters of a source of the Perene amidst a multitude of _quebradas_ Raimondi (op. cit., p. 109) says it “might properly be called the town of the clouds, for there is not a day during the year, at any rate towards the evening, when the town is not enveloped in a mist sufficient to hide everything from view.”

[27] Observer: E. C. Erdis of the 1912 and 1914-15 Expeditions.

[28] Percentages given because the number of observations varies.

[29] Observer: Señor Valdivia. For location of Santa Lucia see Fig. 66.

[30] Observations began on May 12.

[31] For the first half of the month only; no record for the second half.

[32] Boletín de la Sociedad Geográfica de Lima, Vol. 13, pp. 473-480, Lima, 1903.

[33] Boletín del Cuerpo de Ingenieros de Minas del Perú, No. 34, Lima, 1905, also reproduced in No. 45, 1906.

[34] The record is copied literally without regard to the absurdity of the second and third decimal places.

[35] In the Eastern Cordillera, however, snowstorms may be more serious. Prior to the construction of the Urubamba Valley Road by the Peruvian government the three main routes to the Santa Ana portion of the valley proceeded via the passes of Salcantay, Panticalla, and Yanahuara respectively. Frequently all are completely snow-blocked and fatalities are by no means unknown. In 1864 for instance nine persons succumbed on the Yanahuara pass (Raimondi, op. cit., p. 109).

[36] Boletín de la Sociedad Geográfica de Lima, Vol. 27, 1911; Vol. 28, 1912.

[37] Boletín del Cuerpo de Ingenieros de Minas del Perú, No. 65, 1908.

[38] This figure is approximate: some days’ records were missing from the first three months of the year and the total was estimated on a proportional basis.

[39] Christoval de Molina, The Fables and Rites of the Yncas, Hakluyt Soc. Publs., 1st Ser., No. 48, 1873.

[40] See Meteorologische Zeitschrift, Vol. 5, p. 195, 1888. Also cited by J. Hann in Handbuch der Climatologie, Vol. 2, Stuttgart, 1897; W. Sievers, Süd und Mittelamerika, Leipzig and Vienna, 1914, p. 334.

[41] The Physiography of the Central Andes, Am. Journ. Sci., Vol. 40, 1909, pp. 197-217 and 373-402.

[42] Results of an Expedition to the Central Andes, Bull. Am. Geog. Soc., Vol. 46, 1914. Figs. 28 and 29.

[43] The Physiography of the Central Andes, by Isaiah Bowman; Am. Journ. Sci., Vol. 28, 1909, pp. 197-217 and 373-402. See especially, _ibid._, Fig. 11, p. 216.

[44] Travels Amongst the Great Andes of the Equator, 1892.

[45] Geografía y Geología del Ecuador, 1892.

[46] Das Hochgebirge der Republik Ecuador, Vol. 2, 2 Ost-Cordillera, 1902, p. 162.

[47] Contributions to the Geology of British East Africa; Pt. 1, The Glacial Geology of Mount Kenia, Quart. Journ. Geol. Soc., Vol. 50, 1894, p. 523.

[48] See especially A. Penck (Penck and Brückner), Die Alpen im Eiszeitalter, 1909, Vol. 1, p. 6, and I. C. Russell, Glaciers of Mount Rainier, 18th Ann. Rep’t, U. S. Geol. Surv., 1890-97, Sect. 2, pp. 384-385.

[49] Die Sierra Nevada de Santa Marta und die Sierra de Perijá, Zeitschrift der Gesellschaft für Erdkunde zu Berlin, Vol. 23, 1888, pp. 1-158.

[50] For a list of the fossils that form the basis of the age determinations in this chapter see Appendix B.

[51] Eastern Bolivia and the Gran Chaco, Proc. Royal Geogr. Soc., Vol. 3, 1881, pp. 401-420.

[52] The Physiography of the Central Andes, Am. Journ. Sci., Vol. 28, 1909, p. 395.

[53] See paper by H. S. Palmer, my assistant on the Expedition to the Central Andes, 1913, entitled: Geological Notes on the Andes of Northwestern Argentina, Am. Journ. Sci., Vol. 38, 1914, pp. 309-330.

[54] The best photograph of this condition which I have yet seen is in W. Sievers, Südund Mittelamerika, second ed., 1914, Plate 15, p. 358.

[55] Paschinger, Die Schneegrenze in verschiedenen Klimaten. Peter. Mitt. Erganz’heft, Nr. 173. 1912, pp. 92-93.

[56] Hann, Handbook of Climatology, Part 1, trans. by Ward, 1903, p. 232.

[57] S. I. Bailey, Peruvian Meteorology, 1888-1890. Ann. Astron. Observ. of Harvard Coll., Vol. 39, Pt. I, 1899, pp. 1-3.

[58] F. E. Matthes, Glacial Sculpture of the Bighorn Mountains, Wyoming, Twentieth Ann. Rept. U. S. Geol. Surv., 1899-1900, Pt. 2, p. 181.

[59] Idem, p. 190.

[60] W. H. Hobbs, Characteristics of Existing Glaciers, 1911, p. 22.

[61] Op. cit., p. 286. Reference on p. 190.

[62] Corrosion of Gravity Streams with Application of the Ice Flood Hypothesis, Journ. and Proc. of the Royal Society of N. S. Wales, Vol. 43, 1909, p. 286.

[63] G. K. Gilbert, Systematic Asymmetry of Crest Lines in the High Sierra of California. Jour. Geol., Vol. 12, 1904, p. 582.

[64] Op. cit., p. 300; reference on p. 582.

[65] Op. cit., p. 300; see pp. 579-588 and Fig. 8.

[66] The observation at Camaná checks very closely with a Peruvian observation the value of which is S. 16° 37′ 00″.

End of Project Gutenberg's The Andes of Southern Peru, by Isaiah Bowman