Explosive eruptions at Kilauea Volcano, Hawai`i?

Mastin, Larry; Christiansen, Robert; Swanson, Donald; Stauffer, Peter; Hendley, James

The late 1780's were years of great strife on the Island of Hawai'i. Kamehameha, who later became the first king of the Hawaiian Islands, was at war with his rival Keoua. After one of several indecisive battles, probably in 1790, the balance was suddenly tipped in favor of Kamehameha when a natural disaster struck. As a large group of Keoua's warriors traveling with their families passed the crater of Kilauea Volcano, there was a sudden explosive eruption of searingly hot ash and gas. At least 80 and perhaps hundreds of people were killed in the deadliest historical eruption to occur in what is now the United States. Since 1790, only one much smaller explosive eruption has occurred in Hawai'i. During 18 days in May 1924, hundreds of steam explosions from Kilauea hurled mud, debris, and hot rocks weighing as much as 8 tons (7,000 kg) as far as two-thirds of a mile (1 km) from the center of Halema'uma'uthe current crater within the larger volcanic depression (caldera) at Kilauea's summit. Columns of volcanic ash and dust rose more than 2 miles (3 km) into the air, at times turning day into night at the town of Pahala, nearly 20 miles (30 km) downwind. Fortunately, only one person was killed during this eruption, a photographer who ventured too close and was struck by falling rocks and hot mud. Explosive eruptions do not generally come to mind when people think of Hawai'i's volcanoes. Scientists now know that Kilauea in the past has produced numerous explosive eruptions, many dwarfing even the one that occurred about 1790. At least nine layers of volcanic ash, the oldest of which are tens of thousands of years old, are exposed along cliffs in the Hilina fault system, 6 to 8 miles (10 to 13 km) south of Kilauea's summit. Recent work by HVO and Smithsonian Institution scientists has discovered evidence of an explosive eruption that occurred on Kilauea's eastern flank approximately 1,100 years ago, about 500 years after Polynesians first settled in Hawai'i. Explosive eruptions at Kilauea are thought to be caused when water comes into contact with hot rock or magma and flashes into steam. Many of Kilauea's pre-1924 explosive eruptions that produced significant ash deposits probably happened when the volcano's summit crater was so deep that its floor was below the water table, letting ground water seep in to form a lake. Because the water table at Kilauea currently lies about 1,700 feet (1,100 m) below the rim of Halema'uma'u, there is little chance of imminent explosive eruptions. The explosive history of Kilauea continues to be revealed through investigations by USGS and other scientists. Knowledge gained from these studies is being used at HVO to identify communities at risk from eruptions of Hawai’i's active volcanoes. These volcanoes are being closely monitored by HVO scientists so that they can alert the public and local government officials to impending eruptions. The work of HVO is part of the USGS Volcano Hazard Program's ongoing efforts to help protect people's lives and property from volcano hazards in all of the volcanic regions of the United States, including Hawaii, Alaska, Wyoming, California, and the Pacific Northwest.

Explosive eruptions at Kilauea Volcano, Hawai`i?

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