Above: Specimens from the 1965 lava lake in Makaopuhi Crater (about 2 miles east of Mauna Ulu), sampled by drilling, as seen under the< microscope (field of view about 0.05 inch). The amount and kinds of crystals increase with decreasing temperatures as the lava lake cools. (Photomicrographs by Thomas L. Wright.) Top right: Looking about 400 feet down from the rim of Kilauea Iki Crater to the surface of the lava lake formed in the 1959 eruption and a site of drilling studies (oval). Bottom right : Close-up of drilling operations. HVO scientists wear asbestos gloves in handling hot drilling steel. (Photographs by Robin T. Holcomb.)
Abundant studies in recent decades, by remotely controlled deep-sea cameras as well as by small, manned research submarines, demonstrated the widespread occurrence of pillow lavas in areas of submarine volcanism. It was not until 1970, however, that the underwater formation of pillow lava was directly observed. Twice during the 1969-74
Mauna Ulu eruptions of Kilauea, teams of
SCUBA-diving scientists watched and filmed pillow lavas being formed as lava
flows entered the sea. Well-formed pillows also have been studied on the
submarine parts of Kilauea and Mauna Loa, as well as the submerged parts of the
1800-1801 lava flows of Hualalai Volcano off the west coast of Hawaii.
Another common lava product is the ponded flow or lava lake, the formation of which has been described earlier in connection with eruptive style of Hawaiian volcanoes. The surface of lava that is ponded is smooth, broken only by polygonal cooling cracks, formed in much the same way as shrinkage cracks in mud that has been dried by the sun. Lava lakes were formed in Alae (1963 and 1968), Makaopuhi (1965), and Kilauea Iki (1959) Craters. The deep lava lake (350 feet) formed during the November-December 1959 eruption at Kilauea Iki is the only one of these still easily visible and accessible.
The lava lakes have been investigated in detail because they furnish natural crucibles for study of the cooling, crystallization, and chemical change of basaltic lava. These studies have included drilling holes through the solid crust of the lake to measure temperature and other properties and to sample the still-molten lava in the interior. In physical terms, the formation of the lava lake's solid crust by cooling can be compared to the formation of a sheet of ice on top of a body of water during a winter freeze. By 1987, all of the still-molten 1959 lava in the interior of the lake at Kilauea Iki will have solidified, although the internal temperature of the lake will remain hundreds of degrees hotter than the surface temperature for many more years.
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