Shatter Ring on PKK Lava Tube (March 20-22, 2006)
The flow field 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. The shatter ring shown here, informally called the Campout Shatter Ring because it was first seen while HVO geologists were camping near Pu'u 'O'o conducting a multi-day research study, was about 40 meters (130 feet) across. This video shows a series of four uplift cycles over three days. The uplift is obvious during daylight hours, while at night only the associated breakout is visible.
The images that comprise this video were acquired by a time-lapse camera positioned about 1 kilometer (0.6 miles) east of the shatter ring. The image acquisition rate was 1 frame per 10 minutes, and the resulting video is played at 10 frames per second.