Black Chasm Cave is a cave

Cave

A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...

 near Volcano, California

Volcano, California

Volcano is a census-designated place in Amador County, California. It lies at an elevation of 2070 feet . The population was 115 at the 2010 census. It is located at , just north of Pine Grove. The town is registered as California Historical Landmark #29...

 and is a National Natural Landmark

National Natural Landmark

The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...

.

Black Chasm Cave was designated as a National Natural Landmark by the National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

 in 1976. It was recommended for this protection by members of the National Speleological Society

National Speleological Society

The National Speleological Society is an organization formed in 1941 to advance the exploration, conservation, study, and understanding of caves in the United States. Originally located in Washington D.C., its current offices are in Huntsville, Alabama...

 who had made explorations of its numerous chambers in the 1960s.

One of the outstanding geological features of this cave (and a major reason for its NNL designation) is the profusion of helictite

Helictite

A helictite is a speleothem found in limestone caves that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity...

 crystals located in the Landmark Room. These unusual speleothem

Speleothem

A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...

s or formations are probably created by hydrostatic pressure (although there is still some speculation on the exact cause) resulting in horizontal orientation.