Titan reveals cause of the sub-volcano eruption

Subsequent magma injection identified as the trigger for eruption 76, 000 years ago

A piece of volcanic deposits and quartz crystals © Rensselaer Polytechnic Institute / David Wark
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About 76, 000 years ago, a super volcano erupted in North America, burying almost the entire western half of the continent under an ash layer. Now geologists have discovered what triggered this super eruption. The new findings could also help predict future outbreaks of this kind better.

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The Long-Valley Caldera is a 15 by 30-kilometer depression located 20 kilometers south of the California Mono-Lake on the eastern edge of the Sierra Nevada. In the last three million years numerous volcanic eruptions occurred here, including the eruption of the super volcano, which caused the caldera to emerge. The recent eruption, in Mono Lake, is only 250 years back. Scientists at the Rensselaer Polytechnic Institute, led by David Wark, have now explored this region to find out what triggered the massive eruption 76, 000 years ago.

They used the distribution of the trace element titanium in quartz crystals from the deposits of volcanic ash as a "geothermometer". Earlier, scientists from the institute had found out that the titanium allows conclusions about the temperature conditions under which the quartz crystallized.

The investigations of the supervulcan deposits showed that the outer edges of the crystals crystallized in much hotter conditions than the inner regions. According to the researchers, this indicates a subsequent injection of fresh, hot magma from the depths into the magma chamber of the volcano. This "reloading" could have disturbed the balance in the underground and thus triggered the eruption. Investigations showed that this injection must have taken place within a time frame of about 100 years before the outbreak. display

"The Long-Valley Caldera has been intensively researched, but using geothermal quartz as a source of quartz crystals allowed us to gain new insights into the causes of the eruption, " says Wark. "This work also helps geologists understand how supervolcanoes work and what makes them break out. One day, it could also help predict future eruptions better. "

(Rensselaer Polytechnic Institute, 06.03.2007 - NPO)