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Photo glossary of volcano terms

Dike in pit crater at summit of Mauna Loa Volcano, Hawai`i

Photograph by J.P. Lockwood in March 1983

This dike was exposed when a new pit crater formed in about 1880 A.D. in the northeast corner of the summit caldera of Mauna Loa Volcano. The dike is about 1.5 m wide.

Dike
Dikes are tabular or sheet-like bodies of magma that cut through and across the layering of adjacent rocks. They form when magma rises into an existing fracture, or creates a new crack by forcing its way through existing rock, and then solidifies. Hundreds of dikes can invade the cone and inner core of a volcano, sometimes preferentially along zones of structural weakness.

 

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U.S. Department of the Interior, U.S. Geological Survey, Menlo Park, California, USA
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Last modification: Monday, 04-Sep-2000 22:29:27 EDT (SRB)