Read Ebook: The Underworld of Oregon Caves National Monument by Contor Roger J

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INTRODUCTION 1 HOW OREGON CAVES WERE FORMED 3 The Raw Material--Rock 3 Underground Erosion 7 Decoration 14 The Cave's Age 24 Other Cave Features 25 LIFE IN THE CAVES 27 Plant Life 29 THE FUTURE 30 HUMAN HISTORY 30 CONSERVATION AND PRESERVATION 31 GLOSSARY OF CAVE TERMS 34 SUGGESTED READINGS 36 RULES & REGULATIONS 37 ADMINISTRATION 37

INTRODUCTION

Three tired men unsaddled their horses where the mountain stream disappeared into the ground. They had fought their way 15 miles over wild, rugged mountains since leaving Williams Valley at dawn. Yet rest was far from their minds. Hurriedly they stuck tallow candles into lanterns made from tin cans, untied a lariat from a saddle, then walked down the valley. They stopped where the stream, now larger, reappeared from a shadowy crevice under a cliff.

"This must be it," said one of them eagerly, "just like Davidson said." And with mixed feelings of excitement, fear, and the overwhelming grip of adventure, they followed flickering candlelight into the dark opening. Tales of persons lost for days in other caves were fresh in their minds, so they uncoiled a ball of string as they went. Later they could follow it back out.

Thus early visitors responded to the lure of Oregon Caves: to see the unseen and to know the unknown. Today, thousands of people enjoy the caves under less demanding circumstances. Yet the joy of personal discovery endures. For each visitor about to enter the cave, the thrill of learning something new and interesting about the earth beneath us is born anew.

Throughout the world, caves loom large in the scope of history. Early man used them as dwelling and fortifications. Fugitives hid in them and thieves used them to cache their loot. Others have found them fine places to grow mushrooms. During the War of 1812 and the Civil War, Americans mined certain caves for saltpetre which was desperately needed to make gunpowder. Much of our knowledge of long extinct mammals has been gleaned from perfectly preserved remains, and even prehistoric drawings, uncovered by cave-probing scientists.

To most of us, however, the greatest value of caves is the delight of seeing the strange beauties wrought by nature through countless centuries. And from this comes the challenge to understand the imperceptibly slow, relentless forces which produce them. This booklet sketches the processes which form, alter and eventually destroy caves. It is an attempt to share present knowledge with those who visit Oregon Caves National Monument.

HOW OREGON CAVES WERE FORMED

If we could turn back some 180 million years into geologic time, we would find the North American continent a much different place. This was the Triassic Period. Early dinosaurs thrived in primitive forests over much of the United States. The area around southwestern Oregon was not yet part of the continent; it was a shallow arm of the sea. Smoldering volcanoes jutted out as cone-shaped islands or poured forth fumes and lava from the distant mainland.

During quieter centuries the age-old process of life and death went on within the sea waters. Fish, clams, coral--even tiny one-celled creatures too small to be seen--extracted a mineral called calcium carbonate from the water. With it they built bones, shells and skeletons. When these animals died, their hard parts settled to the ocean bottom. Gradually, layers of calcium carbonate were built up.

At the same time certain chemical functions of ocean plants extracted carbon dioxide from the water and caused still more calcium carbonate to precipitate and add to the sediments. The layers deepened. Eventually the weight of overlying sediments and the ocean above compressed them into a rock called limestone.

In different parts of the sea, and under varied conditions, other ocean sediments were deposited. Near the shore, wave-swept sand accumulated and eventually became sandstone. Fine silt and clay carried to the sea by rivers settled in bluish layers which were to become shale. Near rocky headlands, course gravel deposits became cemented into a hard mass called conglomerate.

This steady formation of sedimentary layers was periodically interrupted by volcanic activity. Heavy clouds of volcanic ash and fragments settled into the sea. Molten lava poured into shallow bays or welled up from subsurface volcanoes to mix with calcium carbonate muds. When volcanism subsided, the seas went back to the quiet deposition of limestone. Today at Oregon Caves we find evidence of this interbedding of sedimentary and volcanic materials. An example of such interbedding can be seen above the parking area near the Chateau.

Thus mixed deposits of volcanic and ocean sediments continued to collect for several million years. Apparently this steady transfer of material from one part of the earth's crust to another created a crustal imbalance. The edge of the continent was under a strain. Then, like an accordion, a tremendous folding of the lands along the Pacific Coast occurred.

The floor of the sea was lifted above the ocean's surface to form a new coast line in this vicinity. Violent stresses in the earth's crust created intense heat and pressure which changed, or metamorphosed, the rocks. Shales were altered to slate. Sandstone became quartzite. Limestone became the marble so important to Oregon Caves. Even the volcanic materials were altered considerably from their original form. The resultant geological belt composed of inter-bedded layers of slate, quartzite, marble, and metamorphosed volcanics is known as the Applegate Group.

After the uplift, there was a long period of crustal stability. The folded mountains were eroded away and the area became a flattened plain near sea level. As a result, its streams were sluggish and meandered slowly to the ocean. Then, in various stages, the plain was uplifted in another period of crustal adjustments which produced a flat-topped plateau, so to speak, known as the ancient Klamath Peneplane. This restored the vigor of the stream erosion, which helped at times by glacier sculpture, dissected the plateau into the mountains we know today. The Siskiyou Range surrounding Oregon Caves National Monument is part of the Klamath Mountain System.

Let us focus on one of the ancient marble layers of the Applegate Group, for this is the rock strata in which Oregon Caves were formed. It is actually a narrow, tilted belt, varying in thickness up to 400 feet. It dips eastward into the earth at an angle of about 60? and can be followed in a southwest-northeast direction for about 4 miles along the west shoulder of Mt. Elijah . Examination of the marble layers inside the exit tunnel or the outcrop at the beginning of Cliff Nature Trail reveals many fractures caused by the stresses of upheaval. Some are vertical cracks, but there are also many cross fractures at varying angles.

When tested for chemical composition, Oregon Caves marble samples have averaged 93 percent pure calcium carbonate . Its bluish color is derived from the remaining percentage of impurities. Without these, it would be white. A good example of nearly pure calcium carbonate is the white chalk used on blackboards.

Without this belt of soluble marble, and without the fractures within it, natural processes could not have produced the "Marble Halls of Oregon." It is the foundation, the framework, and the raw material of the caves.

The first requirement in the genesis of Oregon Caves--the right kind of rock--was met. Next came the erosive agent which was to carve it into caverns. This was the flow of underground water.

The present rainfall in this area averages 50 inches a year. During the many thousands of years the caves were forming, the climate may have varied from wetter to drier many times, but it is safe to assume this has always been an area of relatively heavy precipitation. The steep, mountainous terrain and deep-cut valleys of southwestern Oregon are characteristic of aggressive stream erosion that goes hand-in-hand with a healthy supply of rainfall.

Here cracks, pores, and all spaces within the rock are completely filled with water. There are no airspaces. Water movement within the phreatic zone is comparatively slow, varying from a few inches a year to a few feet a day, depending upon the permeability of the rock structure. And the movement is usually horizontal, following the contours of the land in the same direction as surface streams. Eventually this water will find its way back to the surface at a lower elevation where it usually emerges as a spring. It is phreatic water which feeds the mountain streams and rivers many weeks or months after the last rainfall. It might also be pumped from a well for human use. A large portion of the earth's population depends upon well water from these great underground reservoirs.

The water table itself is more stable, but varies somewhat from winter to summer, or during extended periods of unusually wet or dry seasons. Its lowest possible level is ultimately controlled by the elevation of the largest nearby surface stream or lake, which acts as a base level. When the streams and lakes are lowered by erosion, the water table of a given locality keeps pace by slowly sinking until eventually it lies scarcely above sea level.

The enlarged cracks allowed faster movement of water against an increased surface area, and a subsequent increase in solution activity. Partitions between them fell apart and were dissolved. A series of water-filled passages evolved deep underground. Their pattern and orientation followed the pre-cave network of joints and cracks in the original strata. Gradually the openings were further enlarged into the cave system we know today.

There is more to it than that, of course. You may ask, "Why aren't there caves continuously throughout the belt of marble? The joints and cracks are everywhere. And certainly all the marble near the surface has been subjected to ground water action at some time or another. Why are Oregon Caves limited to one particular part of the marble belt?"

The answer to this involves several considerations. To begin with, we do find small cavities and solution cracks throughout the exposed marble. So there has been varying degrees of solution activity nearly everywhere, although not sufficient to produce caverns comparable to Oregon Caves.

So a state of chemical balance tends to develop in normal phreatic drift through the marble. Water saturated with minerals might easily move through many hundreds of feet of marble strata without further enlarging the openings. Instead, it might even deposit some of the dissolved minerals, filling small cracks and veins, possibly even blocking its own passage during dry cycles when phreatic flow is at a low ebb. The "dry" room in the cave is an example of vein filling. Clay, gravel, and other surface sediments can also be washed into the openings, plugging them up and halting further solution for a time. All these factors lead toward a stabilization of the solution process. Openings and small passages continue to be formed, yet normal phreatic movement at Oregon Caves seems to lack the force for large scale cave sculpture.

Several small streams lose their identity and sink into the ground a few hundred yards above the caves. Doubtless, they join the water table inside the caverns to emerge at the entrance as the River Styx . Possibly they aided in the early stages of cave formation in a manner described above.

If stream piracy occurred in the drainage overlying the caves, it might have played an important part in cave carving.

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. . 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.

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.

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.

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.

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 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 . 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.

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. . 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.

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.

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