Kilauea's swelling intrigues scientist
The bulge may herald a summit eruption, a volcano expert says
HILO » Hawaiian Volcano Observatory scientists are monitoring an unusual, 3-mile-wide bulge at the top of Kilauea that may be a harbinger of a summit eruption.
The maximum uplift since early in the year is just 4.3 inches. Still, that amount is so unusual for Kilauea that observatory head Jim Kauahikaua called it "dramatic."
The observatory doesn't have enough information yet to know what it means, although in the long run it could lead to a summit eruption, he said.
While Kilauea's summit periodically puffs up and then sinks, this much bulging is uncommon.
"Over the decades, some (bulges) result in a summit eruption. Most do not," Kauahikaua said. "We don't see this as an immediate cause for concern."
The 4.3-inch bulge is so gradual over a 3-mile distance that scientists aren't sure where its edges are. But the center is immediately south of Kilauea summit's deepest point, Halemaumau Crater.
That point sits above Kilauea's magma chamber, a storage area for liquid rock 2 to 3 miles below the surface.
For the past 23 years, that chamber has collected magma from deep within the earth, then squeezed it sideways 12 miles where it erupts in the area of Pu'u O'o vents.
But in prior years, the magma has erupted more or less straight up instead of going sideways.
One change that could signal a summit eruption would be multiple earthquakes, signaling that underground pressure was building up enough to break rocks.
A lot of earthquakes took place earlier this year, but they tapered off, Kauahikaua said.
As the ground bulges, it also stretches. The observatory has four global positioning system instruments in the area to observe stretching, but only a single tiltmeter there to measure uplift.
Scientists fill in the gaps by surveying, the same way commercial surveyors determine property boundaries, Kauahikaua said.