Bulletin of the National Speleological Society - ISSN 0146-9517
Volume 32 Number 2: 27-40 - April 1970

A publication of the National Speleological Society

The Geology of Moaning Cave, Calaveras County, California
Harry W. Short


Moaning Cave is a composite vertical solution cavity and domepit that has formed in upper Paleozoic limestone of the Calaveras Formation. Although domepit features have developed on the ceiling of the Main Room, solution activity has predominated in forming the cave.

The geological agents responsible for the evolution of this phreatic cave have also limited its horizontal extent. Local faulting has elevated the limestone in which the cave occurs. Faults north and south of and an apparent fault west of the cave entrance control its horizontal extent in these directions. A fracture in the west wall of the Main Room is suggestive of faulting, but evidence of this has been obscured by solution activity.

Regional uplift produced a well-defined joint set, accelerated stream downcutting, and lowered the water table around the cave. The joints in the metamorphosed limestone around the cave carried groundwater to the permeable band of limestone in which it occurs. These waters enlarged the cave to its present size and deposited thick travertine on most of the walls in the Main Room. Undoubtedly, due to the vertical nature of the cave, these waters eventualy reached the water table by draining out through the bottom of the cave.

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