Part 2

The whole process might have involved all three of the above situations in varying degrees, for a “geologically sudden” event may take several thousand years. Several distinct levels of cave erosion indicate that the water table moved along at a certain level for a time, then rapidly dropped to a lower course where it was stable for another extended period. This was repeated until it now stands near the level of the River Styx.

Successively, the caverns at higher levels were drained and left empty. So as your tour climbs from the cave entrance to the highly developed sections near the Ghost Room, you encounter galleries that are progressively older. The first room inside the entrance, Watson’s Grotto, is the best example we have of a cavern “recently” drained.

A word about the River Styx. Above it in several places you can see very smooth walls left by the familiar erosive action of a stream. (See illustration page 14). Most of the cave walls show the more pitted, concave surface left by the acidic dissolving action of phreatic water. The water which produced the main cave system moved much slower than the River Styx, and over a wider area. The stream as we see it did not produce the cave. Rather, the caverns, when drained, left a free flowing course for ground water to channel into. The only true underground streams occur in caves. They are a by-product of the cave-forming process.

_Decoration_

Surface erosion continued to tear away at the mountains. Streams cut their valleys deeper. In response, the water table gradually sank below the level of the caverns and they, in turn, were drained. Air entered the rooms. The basic excavation process was completed except for a few minor changes: In some places, vadose water continued to dissolve away portions of the cave ceilings into dome shapes. In other rooms previously drained, water re-flooded certain portions during wet cycles. And some rooms were filled with clay and gravel brought in from the surface, then washed clean again in later stages.

Most important is the entrance of air, which ushered in the second major stage in cave formation. The unadorned grottoes were now to be decorated. Nature, through the process of _deposition_, next created the eerie beauty which delights today’s cave visitors. In fact the process continues even now, for Oregon Caves are “live” caves, meaning they are still being decorated by natural deposition.

The weak carbonic acid in vadose water kept eating away the roof marble above the caves. Reaching the caverns, drops of vadose water evaporated into the air and left their load of calcium carbonate as thin layers of solid mineral. The amount left by each drop was infinitesimal, yet millions of drops eventually left thick deposits coated on the walls, ceilings and floors of the cave. The crusty white deposits in the Beehive Room are fine examples of deposition by _evaporation_. They were left there in much the same way as the coating in the bottom of a teakettle or steam iron.

However, evaporation is important only near the surface. Deeper inside Oregon Caves the relative humidity averages 98 percent. Evaporation here is almost non-existent. Instead, _loss of carbon dioxide_ becomes the chief agent of deposition. We have learned that vadose water contains 25 to 90 times the normal amount of carbon dioxide found in the atmosphere. Much of it, of course, unites with calcium carbonate to form calcium bicarbonate solution. When this mineralized water reaches the caverns, large quantities of carbon dioxide are able to escape into the air due to the difference in carbon dioxide amounts in the water and air. The chemical balance is upset. For each molecule of escaping carbon dioxide, an equivalent molecule of solid mineral is deposited (see illustrations page 10).

An interesting side effect of the loss of carbon dioxide is experienced by the cave visitor. Although cave air is constantly replenished by outside air through natural exchange, it has a rather high carbon dioxide content due to release of this gas by vadose waters. This partly explains the heavy breathing you find necessary inside the cave, because the nerve centers which control our breathing are stimulated by a high percentage of carbon dioxide in the air we breathe. It also explains the odd “peroxide” odor many people notice when they reach the exit. The odor is oxygen. We notice it because our senses have become adjusted to slightly lower oxygen percentages inside the cave.

Cave deposits are collectively termed _speleothems_. Their variety is infinite: Those left by dripping water are called _dripstone_, and take on two basic forms—if they hang down from the ceiling they are called _Stalactites_, if they grow up from the floor they are _stalagmites_. The two may join together to form a column. Where the water drips rapidly and the loss of carbon dioxide is slow, stalagmite growth is favored because little deposition can take place on the ceiling. If the drip rate is slow and loss of carbon dioxide is rapid, stalactite formation is favored.

Contrasted with dripstone is _flowstone_—smooth layered deposits left along walls and floors by flowing water. In Joaquin Miller’s Chapel, flowstone deposits are many inches thick. (See illustration on page 16). A close look at the structure of dripstone and flowstone reveals six-sided crystals called _calcite_, which is merely the crystalline form of calcium carbonate. (See illustration on page 19). Banded crystal layers in cave deposits are often called alabaster, or cave onyx. These can be easily seen at the “wishing post.”

Other shapes and forms accrue. Flowstone forming on backsloping walls tends to produce graceful sheets called _drapery_. (See illustration on page 17). Reddish bands may develop in drapery where iron oxide is imbedded with the calcite. Contrasted with the pure white layers of calcium carbonate, this gives the appearance of _bacon_. Good examples of “bacon” can be seen in the Ghost Room.

Most shapes and forms of dripstone and flowstone are occasionally duplicated by freezing water. Stalactites form on the edges of roofs, stalagmites form on the sidewalk beneath them, etc. But one of several cave formations which can’t be thus copied is the _soda straw_ (see illustration page 20). Deposition begins as a ring of calcium carbonate around a water drop. The ring has the unique feature of being a single crystal. As more drops leave their deposits, the ringed crystals form one on the other to create a tube. The water continues to seep through the inside of the tube, eventually producing the fragile, crystalline pipe with the obvious name.

The diameter of a soda straw is apparently determined by the specific gravity and surface tension of water, for they are all nearly the same diameter, about one-quarter inch. In a cave in western Australia one soda straw has reached a length of 20 feet, 6 inches, yet is still only one-quarter inch in diameter. If the drip rate decreases, the tip of the soda straw may sometimes seal itself closed.

Some speleothems apparently defy gravity. Now and then internal hydrostatic pressure causes secondary formations to project out from others in unusual directions. These are _helictites_ (see illustration on page 21). A related form is _popcorn_ (see illustration on page 22), the mat of small nodules which coat the “beehive” and other objects in the cave. Also called “cave coral,” popcorn can form under water or along wet walls in response to air currents.

Soft, fibrous mats of calcium carbonate deposited near the surface at Oregon Caves are termed _moonmilk_. In time moonmilk may harden into popcorn mats. Its manner of formation is not fully understood.

At the “Devil’s Washboard,” and at the foot of Paradise Lost, we find still another type of speleothem—_rimstone_—which forms in pools of water. Agitated by dripping or flowing water, some of the carbon dioxide in the pool escapes. The resultant deposition of mineral takes place on irregularities in the bottom of the pool, or creates stone wavelets where the pool spills over. Ridges and dams subsequently build up, often constricting the pool surface (see illustration on page 22). Another type of rimstone, or _cave ice_, develops when flowstone builds up around the edge of a pool and gradually closes across it. The pool may be completely sealed over, just like a pond in winter, except that “cave ice” can never melt.

Cave students are often confused by another deposition found in the form of thin _blades_ jutting out of the wall (see illustration below). They have a woven, crystalline texture. Prior to removal by solution, some of the marble cracks were filled with calcium carbonate. Being less soluble than marble, the sheets of calcite crystals remain for a time after the surrounding rock is dissolved away.

So far we have discussed cave features—_speleothems_—created by deposition of mineral from the solid to liquid, and back to solid state. But certain objects in the caves are simply what remains of a piece of marble after some of it is dissolved away. These are _speleogens_, cave features created by the dissolving of mineral (see illustration page 24 ). They can be striking, but primarily it is the _speleothems_ which make Oregon Caves a thing of wonder and beauty. The zenith of such spectacular development as seen at Paradise Lost leaves little doubt of this.

We have followed the mineral calcium carbonate through many forms: from sea creatures to ocean mud, to limestone and then marble, next to a liquid solution called calcium bicarbonate, and lastly as calcite crystals in cave formations. The size, shape and variety of cave deposits are determined by many factors which seem to prevent any two being exactly alike. Changes in temperature, relative humidity, available carbon dioxide, amounts of vadose water, air circulation, surface tension, permeability of roof rock, vegetation above the cave, bacteria action, and the amount and kind of impurities in vadose water may all combine to vary the nature of cave formations.

_The Cave’s Age_

The many variables make it difficult to accurately estimate the age of cave deposits. We have no way of determining past conditions which have influenced the rate of development. Oh, we know the formations are many thousands of years old, beyond that we can only guess. Some crude examples of known age are the tiny, one-half-inch stalactites formed in the exit tunnel since it was completed some 38 years ago (see illustration below). Bathed in warm, dry air from the outside, they have probably developed much faster than those inside the main cave. Other active formations deep in the cave show very little visible depositing over names written on them by early explorers in the 1880’s. So the true secret of the age of the formations must rest with the cave itself. Perhaps this is best.

_Other Cave Features_

An obvious feature you may see in Neptune’s Grotto is the brown lacework on the walls. They are lines of clay. Molecular attraction causes the clay particles to cling together into what we call _clay worms_. (See illustrations on page 27). Where does the clay come from? Some of it may be washed in from the ground above. The rest of it is the remnant of marble solution. Oregon Caves marble is 93 percent calcium carbonate. The remaining 7 percent is non-soluble clay and remains in the cave after the calcium carbonate is carried away in fluid state. Clay worms are temporary features; vadose water or the touch of a careless hand can easily remove them.

In the Ghost Room we find an interesting object. Projecting from the ceiling is an 8-inch thick slab of angular brown rock. Its edges have been broken, rather than dissolved. This is a _clastic dike_. Evidence is lacking to definitely state its origin or manner of emplacement. But at some time in the past, there was an extensive crack in the marble which was filled by a mudlike material made up of bits of quartz, plagioclase, horneblende, epidote, clay, and other minor ingredients. It may have been washed in from the surface, or it could have been injected from below by earthquake shocks which cracked the marble and forced the pliable material into the cracks.

Eventually it hardened into rock. Due to its non-soluble ingredients, the dike was not dissolved when the Ghost Room was formed. Like the “blades” we discussed previously, it remained as a projection into the room while the marble walls receded under solution activity. Being brittle, it has apparently been broken off periodically by the jar of earthquakes or cave collapse.

Another obvious discrepancy in the marble framework of the caves is the thin layer of slate found in the 65-foot tunnel. This reveals an interruption in the limestone sedimentation of the Triassic sea. A thin layer of shale was deposited between limestone layers. Later, when the limestone became marble, the shale became slate. It should be mentioned here that limestone and shale vary greatly in their contents and often interblend with each other. “Pure” limestone is white. Different shades occur with different amounts of claylike impurities. When the impurities overshadow the limestone, then the rock may be called shale. The whitest marble in Oregon Caves came from the purest limestone. The darker, blue-banded marble is rich in slate impurities.

LIFE IN THE CAVES

If the Indians of southwest Oregon knew of Oregon Caves they left no evidence of the fact. Possibly its remote and rugged setting was too far away from their normal haunts near the fertile valleys and salmon-rich rivers. Or they may have known of the cave, but superstitions forbade their entering it. To our knowledge, Elijah Davidson was the first person to penetrate its depths.

Other creatures used it regularly. Bears, mountain lions, coyotes, bobcats, skunks and other predators found the outer chambers ideal dens or resting places. Within the “twilight zone”—the galleries near the surface where some light penetrates—rodents of several kinds entered freely and even made nests. Today, we find the industrious woodrat still gathering mounds of sticks, leaves, flashbulbs, and hairpins to store near the 110-foot exit. Mice and rabbits are frequently seen in the cave. Occasionally the tracks of the ringtail betray his secretive hunting trips into the cave. In 1935, even a mountain beaver was found in the Ghost Room.

However, there is only one mammal truly adjusted to normal living inside the dark portions of the caves. This is the bat. (See illustration below). There are eight species of bats that use Oregon Caves. Most common is the long-eared myotis. None are abundant, and most visitors do not see them, for this is not a “bat cave” in the same sense as Carlsbad and other caves. Also, the bats prefer the undisturbed sections of the caves, where people seldom enter. In spite of this, they attract much interest and are the subject of much discussion. The only mammal capable of flight, bats are also unique in their ability to fly in total darkness deep within caves.

This latter skill puzzled scientists for many years until, in the 1930’s, it was learned that bats navigate in darkness by echo-location, a system similar to the Navy’s sonar. The animal emits high-pitched squeaks, above the threshold of human hearing. The echo of the squeaks bounces off nearby objects and the bat is able to decipher, from a flood of up to sixty echoes a second, the size, shape, and distance of objects before them. So precise is this system that the animal is able to locate and capture flying insects in pitch darkness. Not only can they navigate in the dark, they can also remember echo patterns that help them to return again and again to the same place deep inside a cave.

They feed at night, eating great numbers of insects. In winter a few of them hibernate in Oregon Caves and may be easily observed clinging head downward from the walls and ceilings for months at a time. During a bat-banding study a few years ago, 750 bats were fitted with tiny aluminum identification bands and released. To date, however, none of these bats have been found elsewhere, nor have any foreign bands turned up here. Some bats are migratory, for each year in late August or September there is an influx of several hundred that may be seen in the caves for only a few days. Then they are gone again.

Certain arthropods—millepedes, spiders, moths and small wingless insects called collemboles—are abundant in the “twilight zone” of the caves, where they feed on organic matter and upon each other. Thus animal life in the cave is more prominent than many people suspect.

_Plant Life_

When the cave lights were installed in 1932, conditions were established for the entrance of another type of life—plants. Carried into the cave by water or air currents, spores of primitive plants could now germinate and live. Near the light fixtures we find interesting colonies. The green coating several feet from the lights are clusters of _algae_. They have no leaves, stems or roots; in fact they are the simplest and most universal of the earth’s green plants. They require much less light energy than the _mosses_ which grow only a few inches from the lights. In one or two places we also find fleshy green _liverworts_ which look like blobs of spilled paint. And now and then we find the cave’s highest type of plants, the _sword ferns_. Diminutive in comparison with their kin outside the cave, these tiny ferns are nevertheless able to survive near the lights which burn at least part of every day during the year.

THE FUTURE

What next? Like lakes and waterfalls, caves are temporary features of the drainage pattern of an area. The same processes which produce them will eventually destroy them. At Paradise Lost we see that an appreciable part of the original room has already been filled with cave deposits. Many side passages in the caves have similarly been blocked off by the accumulation of flowstone.

On the outside, surface erosion will wear away the roof rock until the caverns collapse. The rooms will be filled with sunlight and exposed to rapid weathering. The calcium carbonate that was laid down in the Triassic sea, then lifted into mountains, then changed to calcite cave deposits, will again be dissolved by water and carried back to the sea. We know this because remnants of other caves reveal the pattern of creation and destruction common to all caves. The end will not come at Oregon Caves for thousands or millions of years. But it will come. The work of water and other erosive forces never ceases.

HUMAN STORY

Oregon Caves have been known since a day in 1874 when Elijah J. Davidson went hunting in the Siskiyou Mountains. The story goes that, after killing a deer, he followed his dog to a large hole in the mountain. Here he heard sounds of fighting coming from within. Being undecided as to what to do, he stood waiting—then his dog gave vent to a weird howl, as if in great pain. Hesitating no longer, Davidson rushed into the opening. He soon found the chase difficult to pursue without a light, whereupon he resorted to a few matches that he had in his shot-pouch. Striking match after match, he expected that he would soon be at the scene of the struggle.

Before arriving there, however, his supply of matches gave out, leaving him in the dark. Davidson finally found his way back to a running stream of water, and following it, came to the mouth of the cave. Soon after, the dog came splashing down the creek, unhurt. As it was well on in the evening, Davidson decided to go back to camp and return the next day. Before leaving, however, he placed near the entrance to the cave the buck he had recently killed. He anticipated that a bear would come out for food, eat all it could and then lie down by the remaining part. Returning early the next morning, Davidson found a monstrous black bear lying near the carcass of the deer.

Davidson told others of his discovery, and the cave soon became an attraction for the adventuresome, portions of it being explored and opened. Early interest in commercializing the cave were thwarted by its remote location, far from roads and populous communities.

In 1907, Joaquin Miller, the “Poet of the Sierra,” and Chandler B. Watson, author of _Prehistoric Siskiyou Island_ and the _Marble Halls of Oregon_, visited the cave. They were highly impressed and promoted the cave as the “Marble Halls of Oregon.” Public attention was aroused and the cave was established as Oregon Caves National Monument on July 12, 1909. (See illustration on page 32).

Appreciable public use was not attained until 1922, when an automobile road was completed to the caves. The next year, 1923, the Forest Service granted a concession to the Oregon Caves Company, which has provided public accommodations and cave guide service since then.

In 1933, the Monument was transferred to the National Park System. Concurrently, the completion of the 512-foot exit tunnel that same year greatly improved cave tour circulation. The public use pattern, relatively unchanged for the next three decades, was established after the opening of the concessioner’s chateau building in 1934. The chateau is noted for its charming architecture, complementing the steep, forested setting.

CONSERVATION AND PRESERVATION

Oregon Caves have been set aside as a national monument because of their outstanding natural features. The National Park Service is charged by Congress to provide for the public use and enjoyment of the area “in such manner and by such means as will leave it unimpaired for ... future generations.”

Natural things and natural processes are paramount. Manmade facilities such as trails, lights and steps are necessary to allow visitors to enjoy the cave. But they are kept at a minimum. Your guide will ask you not to touch any of the cave formations. This is to keep them from being stained or broken. Prior to the establishment of the National Monument in 1909, fragile formations were the object of severe vandalism and thoughtless destruction by souvenir hunters (see illustration page 33). It is doubly important to preserve the remaining features for the benefit of those who will come here tomorrow and in later years.

Outside the cave, the Monument is a place where flowers are enjoyed in their natural state and not picked, where birds and wild animals are unmolested by hunters or trappers. The forest is undisturbed. On the trails away from the cave area, the hiker may see animals and plants fulfilling their existence as they did centuries ago. It is to this philosophy that the national parks and monuments are dedicated.

GLOSSARY OF CAVE TERMS

Bacon A thin sheet of calcite drapery having alternating dark and light bands which give it the appearance of a strip of bacon. The dark, reddish bands are usually caused by an iron oxide stain.

Bedding plane The stratification or meeting place of two different layers of sedimentary rock.