Quakes Hint at Volcanic Activity

Thousands of small earthquakes since May indicate that molten rock is moving under the Mammoth Mountain volcano, but an eruption is unlikely, the United States Geological Survey said today.

`` Eruptive activity following this current swarm of earthquakes cannot be excluded, '' agency scientists said, but said the volcano would likely return to a long period of relative calm.

Mammoth Mountain of 11,053 feet, a ski resort in the Sierra Nevada, has risen about half an inch since May 4 and has been rocked by thousands of small earthquakes, but only four were stronger than the magnitude 3 on the Richter scale, said Dave Hill, geophysicist-in-charge of the situation.

No one smelled most of the temblors, some of which were only 1.5 miles deep and often came in rapid gusts.

The most likely explanation is that molten rock, or magma, is squeezed into a vertical crack that extends 3.5 miles to 6 miles below the southern flank of Mammoth Mountain, said Dr.Hill, who presented their findings at the American Geophysical Union's fall meeting here.

This leaf-shaped intrusion is called a dike, and excavations from many old volcanoes reveal that most dikes never burst on the surface, he added.

Posted Date: 2020-06-09

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