• 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.

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    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.

Speleothems

Speleothems, known as drapery at Paradise Lost in Oregon Caves.

Speleothems, known as drapery at Paradise Lost in Oregon Caves.

NPS

Speleothems are depositional features in the cave. They are also known as formations or cave deposits. They do not occur in caves until a cave has an opening to the outside world. Openings allow for the deposition of calcite.

Two processes create speleothems: evaporation and loss of carbon dioxide. The first process, evaporation, occurs when dry outside air enters the cave, evaporating the water and leaving behind the minerals. This process is not common except near entrances and it creates the formation known as cave popcorn. The second process occurs when water entering the cave loses carbon dioxide. When water from the soil enters rock, it is under more pressure. When it reaches the inside of the cave, the pressure reduces and the carbon dioxide can escape. This reduces the acidity of the water, causing water to be supersaturated in calcite, which settles out of the water. This is the slower of the two processes, but is dominant throughout most of the cave.

Did You Know?

From the vista on the Cliff Nature trail you can see the nation's largest serpentine rock outcrops in the distance.

The mountains surrounding Oregon Caves are composed of ocean crust including rocks uplifted directly from the mantle. These mantle rocks make up one of the largest serpentine rock outcrops in the nation.