Southeast wall of the eastern Ukinrek Maar crater. The rhythmically layered, dark gray material visible in the wall consists of more than 15 m (50 ft) of phreatomagmatic tephra. The 1977 tephra sits on an exposure of glacial till capping ash-flow deposits from Ugashik Caldera. The lake has filled the original crater to a depth of more than 30 m (100 ft). In the distance at very top of photograph are debris-avalanche hummocks from an unknown source near the current site of Peulik volcano. Photograph by C. Neal, U.S. Geological Survey, June 4, 1990.