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Overlook Crater vent broadens as rocks become ammo for future blasts

  • STAR-ADVERTISER

    A lava flow in Leilani Estates sets vegetation on fire.

The active vent within Halemaumau Crater has expanded dramatically within the past few weeks, scientists say, mirroring a pattern of activity that happened in 1924 when Kilauea Volcano erupted in a series of explosive events that sent chunks weighing up to 14 tons from the crater.

The size of the vent, commonly called the Overlook Crater, was an estimated 90 to 94 acres as of Saturday, compared with only 12 acres on May 5, according to Steve Brantley, deputy scientist-in-charge of the Hawaiian Volcano Observatory, part of the U.S. Geological Survey.

The estimates were based on satellite imagery taken of Kilauea’s Summit Caldera.

As the lava lake inside the volcano has subsided, the newly exposed crater walls no longer are supported by lava and begin to collapse inward, enlarging the size of the vent. Earthquakes may have contributed to the walls collapsing, scientists say.

On Sunday more than 40 small quakes rattled the Kilauea summit area, most in the range of magnitude 2.5 to 3. A dozen more shook the flanks, including one upslope at magnitude 3.5 and a magnitude-3 temblor offshore.

The pieces that fall to the bottom essentially create an interior cap that keeps gas and steam from escaping, and the pressure buildup contributes to conditions leading to explosions.

That’s what happened in 1924 when Kilauea had its most powerful eruption since the early 19th century, according to scientists. The largest pieces of debris were hurtled about three-fifths of a mile, or more than 1,000 yards, from the crater rim.

Explosions similarly have been occurring in the latest eruption, but not lasting as long and not nearly as powerful as the 1924 blasts, scientists said. Pieces perhaps no more than 20 pounds have been thrown from Kiluaea, scientists estimate.

Still, the pattern of activity is the same as in 1924, they said.

Brantley said the size of the vent in 1924 roughly doubled in about three weeks.

He told reporters Sunday that there could be larger explosions than what has been happening the past few weeks.

“We still think this is a real possibility,” Brantley said.

But scientists dispelled the notion that the current developments would generate a massive explosion akin to what is seen in Hollywood movies, or the cataclysmic 1980 eruption of Mount St. Helens, northeast of Portland, Ore.

“It’s not as if this is building to some big, huge, crazy explosion,” said Scott Rowland, a geologist at the University of Hawaii in Manoa. “It’s not like there will be one big one that everyone is waiting for.”

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