Soon they knew the Davidson story was true, more than true. Crawling from one chamber to another, they found a fairyland of weird grottoes and exquisite stone formations—pillars and spires, drapes, frozen waterfalls and grotesque forms—in shapes and sizes beyond their imaginations. Some they named from resemblance to familiar objects. At others they could only stare in awe and wonder how can it be? Using the rope in steep places, they probed upward into another level of caverns where they were thrilled to find even more elaborate formations. At one place they wrote their names and the date, July 11, 1879. Here and there they saw evidence left by the few others who had entered the cave in the five years since it was discovered by their neighbor, Elijah Davidson. On and on they explored, returning to the entrance only when their last candle was growing short. Outside, stars lighted a midnight sky. Exhausted, happy, they vowed to return, then fell into bedrolls.
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.
Before going on, let us define the word cave as we consider it here. True caves are formed in soluble rock—limestone, marble, gypsum or dolomite. They usually contain some redeposited mineral in the form of stalactites, etc. As most caves occur in limestone, the term limestone cave is often used to describe any true cave, even though it may actually occur in dolomite or marble. The cave-forming process will be basically the same for either type of soluble rock. We exclude from this definition mines, lava tubes, ice caves, and sandstone depressions such as those used by cliff-dwellers in the Southwest. While they are “holes in the ground,” they are formed in different ways than are the limestone type caves, and therefore are not usually referred to in geological discussions of caves.
HOW OREGON CAVES WERE FORMED
The Raw Material—Rock
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.