Pillow Lava
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. The pillow is about 3 feet (1 m) in diameter and has a glassy rim. Figure 21.11 from Porter, 1987.
Photograph by Jack Lockwood, U.S. Geological Survey, June 14, 1982.
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.
