Hawaii's Kilauea volcano could soon send boulders and ash shooting out of its summit crater in the kind of explosive eruption last displayed nearly a century ago. The risk will rise as lava drains from the summit crater down the flank of the volcano, and explosions could occur if the summit lava lake drops so low that groundwater is able to flow into the conduit that feeds magma to the crater, reports the AP. The magma would heat the water, sending steam into the air that would push any accumulated rocks out in an explosion, the US Geological Survey said Wednesday. Don Swanson, a geologist with the Hawaiian Volcano Observatory, said the magma is likely to drop below the water table around the middle of the month. Scientists don't know how long after that happens an explosion could occur.
The receding lava lake resembles conditions seen before a major summit eruption in 1924, said Tina Neal, scientist-in-charge at the USGS Hawaiian Volcanoes Observatory. That explosion killed one person and sent rocks, ash, and dust into the air for 17 days. Kilauea is one of the world's most active volcanoes. It has destroyed 36 structures since it began releasing lava into fissures that opened in a Big Island neighborhood about 25 miles from the summit crater. There are now 14 of the fissures spread through Leilani Estates. In the weeks ahead, the volcano could eject rocks up to two yards in diameter a little less than a mile away, the USGS said. No one lives in the immediate area of the summit crater. But people are continuing to visit Hawaii Volcanoes National Park, which includes the crater and plans to shut down Friday. (Experts say the eruption "could last days, weeks, years.")