Rootless Shield Flank Collapse - July 21, 2007 Eruption (January 26, 2008)

Just after midnight on July 21, 2007, a new fissure eruption broke out on the eastern flank of the Pu'u 'O'o cone (http://hvo.wr.usgs.gov/pressreleases/pr07_21_07.html). Activity quickly focused on the easternmost fissure—Fissure D—and lava began flowing to the northeast (http://hvo.wr.usgs.gov/archive/2007_09_08.html) eventually creating a lava channel perched up to 45 meters (150 ft) above the pre-existing lava surface. On November 21, 2007, lava found an easier path to the surface and broke out from directly over Fissure D on what was, by then, the southern flank of the perched channel (http://hvo.wr.usgs.gov/pressreleases/pr11_21_07.html). Lava flows became focused to the south of Fissure D and quickly began to build a string of rootless shields—low hills of lava formed over a lava tube instead of a volcanic vent. The rapid accumulation of lava did not allow flows to completely cool before being buried by subsequent flows. This resulted in the storage of molten or semi-molten lava within or ponded on the flanks of the rootless shields. At times, shield flank collapses released a body of this stored lava to produce rapidly moving 'a'a flows. The video here shows the rapid release of lava ponded at the top of a rootless shield on January 26, 2008. Steep walls surrounding the ponded lava come into view as the lava drains to the south (to the left). Huge chunks of cooled and coherent lava can be seen being carried along by the advancing 'a'a flow. The terminus of this flow entered the upper part of the mostly-abandoned Royal Gardens subdivision before stagnating.

The images that comprise this video were acquired by a time-lapse camera positioned about 1 kilometer (0.6 miles) south of a steep-sided rootless shield topped by a lava pond. The image acquisition rate was 1 frame every minute, and the resulting video is played at 10 frames per second.