Aerial view of lava pond inside Pu`u `O`o cinder and spatter cone, Kilauea Volcano, Hawai`i

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Photograph by J. Kauahikaua on September 25, 1999

An active lava lake partially fills the crater of Pu`u `O`o. The flat terrace surrounding the lake is about 50 m below the north rim of the crater (right), where most ground observations of the lake are made.

On September 12, magma from beneath Pu`u `O`o and the summit caldera moved into the upper east rift zone. A dike formed between Pauahi Crater and Mauna Ulu. Two days later, a small pond of lava appeared in the crater. It slowly rose, and by September 16 the lake was about 92 m below the east rim of the crater and 50-60 m in diameter. In the next week the lava rose to about 63 m below the east rim and covered much of the crater floor. The lake remained at this approximate level through October, episodically rising 10-15 m and occasionally overflowing onto the top of the adjacent terrace and resurfacing it.