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Photo glossary of volcano terms

Close view of accretionary lapilli from Kilauea Volcano with US dime for scale

These accretionary lapilli on the surface of the Ka`u Desert south of Kilauea caldera. The lapilli formed during explosive eruptions of Kilauea in 1790 A.D. See USGS fact sheet about Kilauea's explosive past.

Close view of accretionary lapilli in tephra layer, Kilauea Volcano

Layer of tephra consisting of accretionary lapilli surrounded by wind-deposited ash in the Ka`u Desert, Kilauea Volcano. This layer is one of several found at this location, about 10 km from Kilauea's summit caldera.

 Accretionary lapilli
Rounded tephra balls between 2 and 64 mm in diameter are called accretionary lapilli if they consist of tiny ash particles. Volcanic ash sometimes form such balls in an eruption column or cloud, owing to moisture or electrostatic forces. Lapilli (singular: lapillus) means "little stones" in Italian.

 

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U.S. Department of the Interior, U.S. Geological Survey, Menlo Park, California, USA
URL http://volcanoes.usgs.gov/Products/Pglossary/AccretLap.html
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Last modification: Monday, 04-Sep-2000 22:27:32 EDT (SRB)