CHAPTER XXXIX

NATURE'S WARNING OF COMING EARTHQUAKES

That there are signs of coming earthquakes which might be read by man, had he sufficient knowledge, there would seem to be but little doubt. These phenomena follow natural laws so that the approach of an earthquake must necessarily be in a definite order both as regards the phenomena which precede as well as those which follow it. There should, therefore, be signs that would enable one to predict its coming, although it must be acknowledged that these signs, so far as we actually know, are indistinct.

It may seem to the unthinking and unobservant that the awful catastrophe of an earthquake comes entirely unheralded; that, apparently, it is not until the earth's surface begins to rock to and fro under the mighty forces that are causing destruction that its presence can be known. There are, however, many reasons for believing that in, perhaps, the greatest number of cases, it might have been foreseen, if greater attention had been given to the slight indications of its probable approach a short time before its occurrence.

It is evident that the conditions of great pressure or stress in the earth's crust which finally result in a disastrous earthquake have been slowly accumulating for a long time, and that when the pressure at last reaches a point where the crust has to yield or slip, the ground is suddenly crushed and tossed to and fro while vast fissures and chasms are produced in the subterranean regions. At those points of the earth immediately above or in the neighborhood of such regions it is possible that there are many signs of the coming quake; and, although indistinguishable by our duller senses, are readily appreciated by the more highly developed senses of the lower animals. Indeed, had we accustomed ourselves to reading the various indications of nature as the lower animals have, we, too, might be able to read these warnings of the coming earthquake.

At great distances from the place where the earthquake starts there would necessarily be a better opportunity for predicting its approach. As already stated, what is called an earthquake does not consist of a single shaking of the ground, but of a highly complex series of shakings. According to Mallet, the following waves start at the same time from the place of origin of an earthquake, when located on the bed of an ocean; i. e., an earth sound wave and a earth wave constituting the earth's shake; a sound wave through the ocean, another through the air; a sea wave called by him a forced sea wave, and finally the great sea wave.

These waves reach a distant point in the following order: the sound wave through the earth and the great earthquake or shake which produces the damage. Then a smaller sea wave called the forced sea wave. This is followed almost immediately by the sound wave through the sea. Next come the air sound wave and finally the great sea wave; which, rushing in on the shore, sweeps nearly everything before it.

In other words, the disturbances produced by the great earthquake follow in this order of sequence. If, therefore, the great earthquake wave proper transmitted through the earth should for any reason be delayed in reaching a distant place, the great sound waves should be able to give warning of the coming disturbances.

Again, as we have already seen, the earthquake wave is preceded by a number of preliminary tremors, and is followed by a number of after tremors or _earthquake echoes_. Since, therefore, the preliminary waves reach a place first, it would seem that the approach of an earthquake must be heralded by the preliminary tremors. These, perhaps, at least in part, enable the lower animals to detect its coming.

Again, in almost all instances there are a number of preliminary shocks that precede the great earthquake shock. Some of these preliminary shocks continue at intervals for several days or even longer. Sometimes, indeed, these subterranean sounds fail to be followed by earthquakes. Milne thinks that these sounds are caused by the preliminary tremors which precede the principal shock of the earthquake and that they reach the place first. Here again then it is evident that, were we able to interpret properly these sounds, we would probably be able to foretell the coming quake with a fair degree of certainty.

There would appear to be no reasonable doubt that in some manner which we have not yet been able to discover, but probably along some of the lines indicated above, animals are capable of recognizing a coming earthquake. Long before the coming of the catastrophe they are said to exhibit extreme terror, and in many cases appear to seek the companionship of man, as if for protection.

That the senses of smell and hearing are far more acute in the lower animals than in man no one can reasonably doubt. The manner in which a trained dog can follow a scent, for a long time after the animal or thing producing it has passed, far exceeds the power of scent possessed by man, and it is more than likely that this same power is possessed by all animals who live upon or prey upon other animals. It is probable that faintly odorous vapors or gases escape from the crust shortly before the great shock occurs, and that these faint odors are warnings to the animals of the approaching calamity. The sense of hearing also is much more acute in the lower animals.

Daubeny is evidently of this belief, as will be seen from the following:

"These gases and vapors (alluding to emanations given off from the ground during earthquakes) exert an influence on the barometer, which does appear to be indirectly affected by the earthquake. Then, similar properties also may occasion that uneasiness which animals are said to evince before any such event. Thus, according to the accounts of some writers, rats and mice leave their holes, alligators seek the dry land, quadrupeds snuff the ground, and manifest such signs of the impending calamity that in countries where earthquakes are common, the inhabitants take the alarm in consequence, and escape from their houses. It is right, however, to add, that more recent authorities dispute altogether the correctness of these statements."

Dutton doubts the ability of animals to foretell coming earthquake shocks.

But that the lower animals do exhibit signs of fear at the approach of an earthquake has been repeatedly asserted by good observers.

Hamilton, who made a careful examination of the neighboring country during the great earthquake at Calabria, asserts that horses and oxen during the shocks extended their legs widely in order to avoid being thrown down, "and that hogs, oxen, horses, and mules, and also geese, appeared to be painfully aware of the approach of the earthquake of Calabria; and the neighing of a horse, the braying of an ass, or the cackling of a goose, even when he (Hamilton) was making his survey (after the occurrence of the great earthquake shock), drove the people out of their temporary sheds in expectation of a shock."

It is asserted that birds appear to be especially sensible to a coming earthquake shock. That geese will quit the water in which they were swimming before the earthquake and will not return to it. It is quite possible that these birds with their heads immersed in the water can hear the distant murmurings long before they become audible in the air.

Von Hoff makes the following statement:

"It has been remarked that at such times (immediately before the coming of an earthquake shock), domestic animals showed a decided uneasiness, dogs howled mournfully, horses neighed in an unusual manner, and poultry flew restlessly about. These latter phenomena might easily be produced by mephitic vapours, which often ascend to the surface of the earth before the breaking out of an earthquake."

Mallet states that there is abundant evidence that earthquake shocks, even when not of very great intensity, produce nausea in both men and women. This would seem natural, since, as everyone knows, until one is accustomed to sea-voyages, merely to be tossed to and fro by the motion of the waves results in the production of sea-sickness.

It has been also noticed that during earthquakes fish which under ordinary circumstances live in the mud at the bottom of bodies of water come near to the surface and at such times can be caught in great numbers.

Mallet cites the following effects produced by earthquakes:

"Amongst the effects supposed to be produced by the earthquake on the atmosphere were reckoned tempestuous winds, thunder-storms, meteors, coldness of the air, severe winters, heavy rains, miasmata, producing diseases and affecting vegetation. A very remarkable instance of the latter is quoted, namely, that in Peru, after the earthquake of 1687, wheat and barley would not thrive at all, though formerly the country was remarkably favourable for them."

Sir Charles Lyell notes the following phenomena attending earthquakes:

"Irregularities in the seasons preceding or following the shocks; sudden gusts of wind, interrupted by dead calms; violent rains at unusual seasons, or in countries where, as a rule, they are almost unknown; a reddening of the sun's disk, and haziness in the air, often continued for months; an evolution of electric matter, or of inflammable gas from the soil, with sulphurous and mephitic vapours; noises underground, like the running of carriages, or the discharge of artillery, or distant thunder; animals uttering cries of distress, and evincing extraordinary alarm, being more sensitive than men to the slightest movement; a sensation like sea-sickness, and a dizziness in the head, experienced by men. These, and other phenomena, less connected with our present subject as geologists, have recurred again and again at distant ages, and in all parts of the globe."

THE END

FOOTNOTES:

[Footnote 1: A point on the other side of the earth directly opposite a given point.]

[Footnote 2: A fracture of a stratum, or a general rock mass, with a relative displacement of the opposite sides of the break.

The plane or fracture of a fault, known as the fault-plane, is seldom vertical. The higher side is called the heaved or upthrow side; the opposite side the thrown or downthrow side.]

[Footnote 3: _Tectonic Earthquake_. An earthquake due to the sudden slip of faulted strata.]

[Footnote 4: _I. e._, burnt out mountain, extinct volcano.]

[Footnote 5: _Epicentre._ A point on the surface of the earth vertically above the point of origin of an earthquake, or the place where it starts.]

Transcriber's Notes

Obvious printer errors have been silently corrected.

Some illustrations have been moved to paragraph breaks.

Page 43: Kamehamoha could be a typo for Kamehameha.

Page 68: Changed "salter" to "saltier." (Orig: another with water salter than the sea,)

Page 76: Changed "Ena" to "Etna." (Orig: during his time Mt. Ena had lost so much of its height)

Page 115: "eruption during the winter of 1841-43," could be a typo for 1841-42 or 1842-43.

Page 122: "Mont Pelée" could be a typo for "Mount Pelée."

Page 136: 43° C." (109° 4' F.). could be a typo for (109.4° F.).

Page 341: Changed one-eight to one-eighth. (Orig: It was equal to one-eight of a Roman mile)

Retained the following spelling variations:

Page 49: The largest volcano in Iceland, the Dyngjufköll, Page 57: The largest volcano in Iceland is Dyngjufjoll.

Pages 52, 193, 311: Geikie Page 181: Geicke

Pages 17, 156, 257: Hindostan Page 165: Hindustan

Page 63: Lucullis Page 76: Lucullus