VHP Photo Glossary: Lava balls

Accretionary lava ball

Photograph by J.D. Griggs on 13 June 1983

Accretionary lava ball


Photograph by J.D. Griggs on 2 July 1983

Glowing accretionary lava balls (bottom, 0.75 m in diameter) in front of moving `a`a flows. Both flows were erupted from Pu`u `O`o vent on the east rift of Kilauea Volcano, Hawai`i.

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Accretionary lava balls are roughly spherical masses that form on the surface of an `a`a flow. They range in size from a few centimeters to several meters in diameter. Lava balls grow when a small fragment of solidified lava rolls along the surface of an active flow and lava sticks or accretes to its surface. The growth of a lava ball is similar to the way a giant snowball grows when soft, sticky snow adheres to its surface as it rolls downslope.

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