Earthquakes Intensify Volcanic Eruptions
The Merapi volcano erupting on May 11, 2006 - two weeks prior to the Java earthquake - as captured by Space Imaging’s IKONOS satellite. A faint volcanic plume (gray) extends from the volcano’s summit toward clouds (white).
Credit: GeoEye

The violent rumblings of a major earthquake can almost immediately intensify nearby volcanic eruptions, scientists said today.

Three days after a 6.4-magnitude earthquake shook Indonesia's Java Island in May 2006, killing nearly 6,000 people, the intensity of two of the island's ongoing volcanic eruptions increased sharply. The heightened activity lasted for about nine days.

"During this period, we found clear evidence that the earthquake caused both volcanoes to release greater amounts of heat, and lava emission surged to two to three times higher than prior to the tremor," said study lead author Andrew Harris of the University of Hawaii.

To detect the intensity of the eruptions, satellites monitored the heat output of the two volcanoes, Merapi and Semeru, which were roughly 50 kilometers (31 miles) north and 280 kilometers (174 miles) east of the earthquake epicenter, respectively.

The researchers believe that underground stresses from the earthquake's seismic waves pumped magma from under the volcanoes up to the surface.

"The responses at Merapi and Semeru lagged about three days behind the triggering earthquake, which may reflect the time it took the change felt by magma residing at deeper level to be transmitted to the surface," Harris said.

The researchers concluded that earthquakes have the power to intensify ongoing eruptions, but whether they can trigger new eruptions remains an important question.

The study, detailed in January 25 issue of the journal Geophysical Research Letters, was announced today by NASA. It also shows that satellite monitoring may be able to help predict volcanic eruptions.

A study last year revealed that the weight of Hawaiian volcanoes can trigger earthquakes.

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