• Speleothems in Miller's Chapel.

    Oregon Caves

    National Monument Oregon

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  • Cave Tours Closed for Season

    Cave Tours are closed for the winter. Tours will resume April 26, 2014. All trails on the monument remain open.

  • Road Work

    Crews are removing brush along highway 46 beginning in the lower parking lot and moving down the highway. Work is scheduled to last until April 20, 2014; expect delays.

Speleogenesis- Creation of Cave


Over several million years, the belt of marble within the Siskiyou Mountain cracked as the land uplifted and folded. At the same time, the top of the mountain weathered and exposed the marble to the surface of the earth. A forest grew over the marble and in the forest soil, fungi, bacteria, and mold decomposed dead plants and animals releasing carbon dioxide. Precipitation percolated through the soil and captured the carbon dioxide to create carbonic acid. This mild acid is the same stuff that gives soda pop its fizz.

The acidic water then chemically weathered the marble bedrock as it traveled downward through the cracks and holes in the rocks. Ground water moved downward until it reached the water table--an area where all available pore space in rocks are filled with water. The greatest amount of marble was dissolved just below the water table where the highest concentration of carbonic acid occurred. Water then spreads sideways along the cracks in the bedrock and the carbonic acid slowly dissolved the marble. Over hundreds of thousands of years, the carbonic acid enlarges small cracks into larger cavities as the marble was carried away (eroded) in solution. The process of dissolving marble and opening up spaces within it is called speleogenesis. Speleogensis is derived from the Greek words "spelaion" (cave) and "genesis" (beginning).

Did You Know?

Scorpion under ultraviolet-DYK

Scorpions fluoresce or glow under ultraviolet (UV) black light. They can glow electric green or blue. Scorpions fluoresce because they contain a fluorescent protein in the upper layer of their exoskeleton. This layer is like your fingernail, but even more protective and tough. The special protein inside is thought by scientists to serve as an ultraviolet sensitivity mechanism, perhaps allowing the scorpion to avoid burning itself by staying exposed too long to damaging light levels.