1. Accretionary lapilli on the surface of the Ka`u Desert south of Kilauea caldera.
1. Accretionary lapilli on the surface of the Ka`u Desert south of Kilauea caldera.
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 quot;little stonesquot; in Italian.
The lapilli shown in these images formed during explosive eruptions of Kilauea in 1790 A.D. For more information, please see the USGS fact sheet Kilauea's explosive past. The layer shown in image 2 is one of several found at this location, about 10 km from Kilauea's summit caldera.
2. Layer of tephra consisting of accretionary lapilli surrounded by wind-deposited ash in the Ka`u Desert, Kilauea Volcano.