"Ballistic blocks" the size of microwave ovens shot from Hawaii's Kilauea volcano Wednesday in what may be the start of explosive eruptions that could spew huge ash plumes and hurl smaller rocks for miles, the U.S. Geological Survey said.
Such eruptions, last seen nearly a century ago, have been a looming threat since Kilauea, one of the world's most active volcanoes, erupted nearly two weeks ago.
Explosions in Kilauea's crater sparked an aviation red alert due to risks the ash plume could blow into aircraft routes and damage jet engines.