Roger J. Contor

“ 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. ”

“ Once the amount of carbon dioxide dissolved in the water has united with an equivalent amount of calcium carbonate (marble) , the solution is saturated. No more marble can be dissolved until additional carbon dioxide is absorbed by the water. If the solution loses some of its carbon dioxide into the air, then an equivalent amount of calcium carbonate must be redeposited as solid stone. The balance can be delicate. In an underground pool of mineralized water, solution may be going on at one end of the pool and deposition at the other. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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.
Blade formation
So far we have discussed cave features—speleothems—created by deposition of mineral from the solid to liquid, and back to solid state. ”

“ 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. ”

“ 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 12 toward a stabilization of the solution process. ”

“ Where does the clay come from? Some of it may 26 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. ”

“ 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. ”

“ Pressure of the overlying rocks is so great that open spaces capable of holding water cannot exist. So the earth’s crust contains available well water only in restricted zones not far from the surface. The top of the zone of saturation is called the water table. It is here that the most rapid flow of phreatic water occurs, for the joints and interspaces are wider nearest the surface. Between the water table and the surface is the vadose zone, in which the spaces are partly filled with water and partly filled with air. ”

“ 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. ”

“ Nature required many thousands of years to create these stalactites. A thoughtless person needed only a few moments to destroy them.
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. ”

“ 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. ”

“ 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. ”

“ 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 25 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. ”

“ 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. ”

“ 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?” ”

“ 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. ”

“ 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. ”

“ If the drip rate is slow and loss of carbon dioxide is rapid, stalactite formation is favored.
Formations on page 16
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. ”

“ They 24 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. ”

“ 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. ”