A visitor, standing on the bench at the time of the collapse, disappeared into the ocean. Dark areas are black sand. Photograph by Christina Heliker, U.S. Geological Survey, August 25, 1994. Pillow lavas are also found near the summit of Mauna Kea These pillow lavas were produced by a subglacial eruption that occurred 10,000 years ago. Figure 21.11 from Porter, 1987.
Pillow lavas can also form when flows enter a river or lake.
The pillows in the photo formed in the Wailuku River above Hilo, Hawaii about 3,500 years ago. The round cobbles were transported by the river. Photograph by Jack Lockwood, U.S. Geological Survey, June 14, 1982. Aa lava on pahoehoe, Hilina Pali, Kilauea. Photo by Steve Mattox, 1988.