Hundreds of Quakes Show Mount St. Helens Recharging

Mount-St-Helens
A swarm of earthquakes has been recorded beneath volcanic Mount St Helens, although an eruption is not seen as imminent. Andy Clark/REUTERS

Mount St. Helens is very much an active volcano, with new data showing it is filling with magma once again.

The U.S. Geological Survey reports that there have been 130 small earthquakes beneath the volcano in the last eight weeks, and that the seismic activity has been increasing since March to the current average of about 40 temblors per week.

Luckily, this swarm of quakes doesn't mean that an eruption is necessarily imminent. The quakes are quite small—between magnitudes of 0.5 and 1.3—and pretty far beneath the volcano, at depths of 1.2 to 4 miles. These are small enough that they couldn't even be felt if you were standing right above them, the survey notes.

The quakes are caused by "recharging," meaning that magma is flowing upward toward the volcano. As this molten rock squeezes through cracks in the rock, it produces small quakes.

Mount St. Helens has become one of the best-monitored volcanoes in the world since its eruption on May 18, 1980, which was the most devastating of any in the history of the United States. A swarm of 10,000 earthquakes preceded that event, according to the Christian Science Monitor, but those quakes were larger, and the eruption was ultimately triggered by a 5.1 magnitude temblor.

Aside from the quakes, the agency hasn't detected any indications that are often seen before eruptions, such as inflation of the volcano itself or anomalous gases. "There is absolutely no sign that it will erupt anytime soon," the USGS said of Mount St. Helens in a statement.

Hundreds of Quakes Show Mount St. Helens Recharging | Tech & Science
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