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Geology of Mojave National Preserve: Mitchell Caverns

View of tilted Paleozoic limestone As you drive toward Mitchell Caverns, notice the tilted gray layers of rock that dominate the skyline ahead. These rocks are mostly ancient limestone (Paleozoic) like the rock you saw at the Evidence of Ancient Life field trip stop. This sequence of limestone layers is similar to those found across much of the southwestern U.S.including Grand Canyon National Park and Lake Mead National Recreation Area.

Look closely at the rock along the trail to the cave and you will see fusulinid fossils; intricate rice grain-sized and shaped shells of prehistoric amoebas.

Many people visit Mitchell Caverns to admire the intricate dripstone formations (speleothems) that decorate the interior walls. These decorations formed during the last of three main stages in the development of this subterranean maze. Stage 1 initial cave formation via dissolution of limestone by acidic water.

The first stage is the formation of the limestone itself (visit Lake Mead's Paleozoic geology page to learn more)
The second stage, the formation of the caverns themselves, did not begin until late in the geologic history of this region. A few million to a few hundreds of thousands of years ago, when the climate was wetter, the porous limestone that now forms the walls of Mitchell Caverns was saturated with water. Unlike pure water, water moving through the ground contains carbonic acid that forms when CO₂ is picked up from the air and decaying plants. The weakly acidic water can slowly dissolve limestone.

Stage 2 cave formation via dissolution of limestone by acidic water. The acid water first attacks the limestone along weaknesses between rock layers and fractures. Isolated patches of limestone dissolve first, but as the acid continues to eat away the rock, water-filled cavities begin to form. Given enough time, cavities will grow and meet to form interconnected maze-like caverns.

Stage 3 ground water lowers, exposing cave to atmosphere.

Cave walls remain smooth until the level of the ground water drops below the caverns. Then the process of interior decoration begins! Bit by bit limestone is gradually redeposited by dripping water to form the stunning interior of Mitchell Caverns. Click the magnifying glass to learn more about Mitchell Caverns' dripping decorations.

Dig Deeper: Carbonate Rocks of the Mojave and Associated Landforms

|Inside Mitchell Caverns | Mitchell Caverns image gallery | General information on caves |

View geologic map of area (large files!)
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Geology in the National Parks home \| U.S. Department of the Interior \| U.S. Geological Survey Privacy statement / General Disclaimer USGS Western Earth Surfaces Processes Team Webmaster http://geology.wr.usgs.gov/docs/usgsnps/index.html This page was last updated on 01/13/04