Steam explosion blasts lava fragments onto sea cliff, building a littoral cone

Photograph by L. Keszthelyi on 23 February 1996

Littoral cone

A cone of lava fragments built on the surface of a lava flow pouring into a body of water, usually the sea, is called a littoral cone ("littoral" refers to a shoreline). Lava entering the ocean heats and boils seawater, often generating steam explosions that hurl tephra onto the shore, including spatter, bombs, blocks, ash,, lapilli, and, rarely, limu. As the various tephra accumulates on the shoreline, a well-developed cone may be created.

Tephra generated by steam explosions built the small littoral cone, shown here, along the southern shoreline of Kilauea Volcano, Hawai`i. Note pahoehoe flow nearing the ocean below the cone.

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