When lava is ponded, as in a lava lake, the top portion cools first and forms a crust. The molten material below may then drain out, or simply shrink during cooling, and the unsupported crust may collapse under its own weight. In this photo a relatively round lava lake's crust has collapsed into large, pie-shaped wedges.

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	Created: August 4, 2000 Author: Dave Bunnell