Volcano Watch: Did groundwater trigger explosive eruptions at Kilauea?

Explosive eruption columns of ash rising from Halemaumau at 11:15 a.m. on May 18, 1924, (top), and at 11:05 a.m. on May 15, 2018, (bottom), look similar. Researchers are re-evaluating early assumptions about the role groundwater played in triggering these explosive eruptions at the summit of Kilauea Volcano and are now looking at the build-up of gases from retreating magma as a likely trigger. (Courtesy photo/USGS)

VOLCANOES NATIONAL PARK — In February 1924, the surface of the lava lake at Halemaumau dropped rapidly and disappeared from view. Throughout March and April, the crater floor subsided as magma moved out of the summit reservoir into the East Rift Zone. By May 6, 1924, the floor of Halemaumau had dropped more about 600 feet below the crater rim.