When Kilauea Volcano Collapses

26 06 2007

Last month a large chunk of the Kilauea Volcano splashed into the sea. When the Lae`apuki lava delta, on the volcano’s south shore, partially collapsed on May 10, it formed a large scalloped bay. Although scientists initially estimated the area of collapse to be 6 hectares (16 acres), the total area of collapse is now estimated at 9 hectares (23 acres), according to USGS Hawaii Volcano Observatory.

Further collapses may occur without warning, according to USGS.

How The Collapse Happens

When pahoehoe lava enters the ocean for extended periods of time, new land is created in the form of a fan-shaped platform known as a lava delta. Lava pouring into the ocean from either surface flows or lava tubes cools rapidly, usually shattering into sand- to block-size fragments. These fragments accumulate along the submarine slope to form a loose foundation that will eventually support overlying lava flows that build the delta above sea level.

When the lava fragments accumulate on a relatively steep submarine slope, the leading edge of a lava delta will collapse frequently to form a series of submarine landslides. These collapses can sweep unwary visitors into the sea and trigger strong explosions. A lava delta will grow both laterally and seaward until a collapse occurs or the supply of lava to the ocean is interrupted.

Below: Pahoehoe lava entering the ocean at a new location either oozes across a cobble or black sand beach or spills over a sea cliff, typically 1 to 5 m tall. As waves splash over the advancing lava, the surface of the molten stream cools quickly and shatters into small, glassy fragments.

Pahoehoe lava enters ocean

Lava reaching the ocean is cooled so rapidly by the incoming waves that it “freezes” to form to a black glass and shatters into sand- to block-sized fragments that accumulate along the submarine slope just offshore. These loose lava fragments form the unstable foundation for all subsequent lava flows and loose debris, eventually resulting in dangerously unstable land.

For more photos, as well as diagrams of the process, visit When Lava Enters the Sea: Growth & Collapse of Lava Deltas at the Hawaiian Volcano Observatory of the USGS.

Situated on the southeastern side of the Big Island of Hawaii, and known as the home of Pele, the Hawaiian volcano goddess, Kilauea has erupted 34 times since 1952. The latest period of eruptive activity has been ongoing since 1983, the volcano’s longest in more than 600 years, with its most recent eruption on May 24.

Sources: Carolyn Gramling for Geo-TimesHawaiian Volcano Observatory (USGS)

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