Sunday, June 24, 2007

Earthquakes shaking Kilauea volcano may be clue to lava activity

Hundreds of small earthquakes that suggest that magma is on the move under the surface of the Kilauea volcano sent scientists and national park officials scrambling over the weekend and prompted the rare closure of most of Hawaii Volcanoes National Park.

The earthquake swarm began at 2:15 a.m. Sunday, with more than 260 recorded in 17 hours. Another nine were reported on the island of Hawaii between midnight and 4 a.m. today, as well as one 26 miles offshore. The largest of those registered a 3.2 magnitude at the U.S. Geological Survey at the Hawaiian Volcano Observatory.

Eleven campers and some livestock were evacuated from portions of the park as rangers monitored the unusual earthquake activity for signs of a shift in the ongoing Kilauea eruption. Fresh cracks were reported in nearby roads.Park Ranger Mardie Lane said it was the first time she could recall since about 1999 that seismic activity caused by underground magma movement prompted the park to take such extensive precautions.

Park officials planned to reassess the situation today.“It looks like the rift has expanded a bit, possibly to accommodate magma, and the earthquakes are accompanying that process,” said Jim Kauahikaua, scientist-in-charge of the volcano observatory.Steve Brantley, deputy scientist-in-charge for the observatory, said the center of the earthquakes was about a mile southwest of Mauna Ulu, but during the day, the hub of the seismic activity migrated about 3 miles down the east rift zone toward Pu’u ’O’o, the source of the ongoing eruption.

At the same time, the summit area of Kilauea volcano began to deflate or contract, another clue that magma is shifting from beneath the summit to some other part of the volcano, Brantley said.All the activity raised concerns for the National Park Service, which closed the 18-mile Chain of Craters Road that visitors normally use to reach lowland areas where lava flows into the sea.

Lane said more than 1,000 people may drive at least partway down that road on a typical weekend day.With the apparent new movement of magma, Lane said, the concern was that if lava suddenly burst to the surface in an unexpected area, it could cut roads and trails, spew poisonous fumes or start brush fires that could pose a threat to visitors.“It’s a hidden hazard,” Lane said.

“Our job is to have this place open, but not at the risk of anybody’s life.”Brantley said that although the hub of the earthquake activity shifted downslope during the day Sunday, the Chain of Craters Road and other areas farther downslope from the earthquakes could still be at risk.“Assuming that our inference is correct” — that the earthquakes signal magma movement — “the magma could head to the surface at any time,” he said.

Kauahikaua said the observatory was watching the situation closely. There are several possible outcomes, he said.“The most dramatic would be some sort of surface breakout of lava here near Mauna Ulu,” Kauahikaua said. “The best would be, of course, that it’s just going to remain underground.”

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