East Lae'apuki Shatter Ring (October 16, 2006)

The lava-tube feature seen here is called a shatter ring. Shatter rings are circular to elliptical volcanic features, typically tens of meters (yards) in diameter, which form over active lava tubes. They are typified by an upraised rim of blocky rubble and a central depression. Dozens of shatter rings have been identified on volcanoes in Hawai'i, and have also been reported from basaltic lava fields in Iceland, Australia, Italy, and the mainland United States. They form when lava pressure in the tube repeatedly exceeds the strength of the overlying rock. Repeated flexing of the lava-tube roof piles up rubble around the edges of the mobile area. This shatter ring, about 55 meters (180 feet) long and and 2.5 meters (8 feet) high was active from late September to mid-October 2006. The center of the shatter ring, which becomes visible as the shatter ring uplifts, started out about a meter (3 feet) lower than the lava surface outside the shatter ring. Thus, the center of the shatter ring uplifted about 5 meters (16 feet) during this event. Lava emerges from the base of the shatter ring when the lava tube roof is pushed up out of the way and is further evidence of the overpressurization of the tube.

The images that comprise this video were acquired by a time-lapse camera positioned on a small mound of lava about 75 meters (245 feet) east of the shatter ring. The image acquisition rate was 1 frame per minute, and the resulting video is played at 10 frames per second.