HILO, Hawai'i — A 12.5-acre section of the newly formed lava delta at Hawai'i Volcanoes National Park slumped into the ocean over the weekend, with images of the collapse captured by time-lapse camera.

Visitors have been banned from a 30-acre outcropping at the East Lae'apuki delta since June 30 because cracks in the cooled lava suggest the area could drop into the ocean at any time, potentially causing steam explosions and forcing scalding water and boulders to wash back onto shore.

Scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory noted the weekend event after retrieving the time-lapse photos Tuesday.

The action began shortly after 1:30 a.m. Saturday with the rapid collapse of a 100-yard-wide slice at the forward edge of the delta. It generated waves large enough to push boulders back on the surface of the lava, according to an observatory report. A steam plume generated by the collapse blocked the camera for almost 20 minutes, and then more chunks of cooled lava fell into the water accompanied by steam explosions.

Scientists reported yesterday that surface flows on the delta remain active, with several small streams of lava pouring into the sea.