Mount Rainer is rattled by more than 300 earthquakes. It's the largest swarm in years.
As of Thursday, July 10, 334 earthquakes had been identified at Mount Rainier by the Pacific Northwest Seismic Network (PNSN), Cascades Volcano Observatory Public Information Officer Holly Weiss-Racine told USA TODAY. The swarm, a cluster of earthquakes occurring in the same area in rapid succession, began in the early morning of Tuesday, July 8.
Scientists do not have any concerns about the earthquakes, the Cascades Volcano Observatory states. The largest so far was recorded at a magnitude of 2.3 on Wednesday, July 9.
Weiss-Racine said the rate peaked at 26 earthquakes per hour on the morning of July 8 and has decreased to "a few" per hour on the morning of July 10.
The PNSN is continuing to locate earthquakes a part of the swarm. Updates are shared on the PNSN website at pnsn.org/volcanoes/mount-rainier.
The earthquake swarm is not dangerous to hikers on the mountain and has posed no indication for concern, the Cascades Volcano Observatory wrote in a news release.
As of July 10, the largest earthquake in the swarm was recorded at a magnitude of 2.3.
According to Michigan Technological University, earthquakes of a 2.5 or less magnitude are common – millions happen each year – and are not usually felt.
Earthquake guide: Earthquakes happen all the time, you just can't feel them.
About nine earthquakes per month are common at Mount Rainier, according to the Cascades Volcano Observatory. Earthquake swarms typically occur one or two times a year at the volcano but are not as large.
The last large earthquake swarm at Mount Rainier occurred in 2009 and lasted for three days. The swarm resulted in more than 1,000 earthquakes and the largest was of a 2.3 magnitude, according to the U.S. Geological Survey.
The Cascades Volcano Observatory states that Mount Rainier is not "due" for an eruption and no signs point to an eruption at this time.
But generally, earthquakes can be related to subsequent volcanic eruptions, according to the U.S. Geological Survey. However, the circumstances have to be just right.
For a volcano to be triggered into eruption by earthquakes, a volcano must have enough "eruptible magma" and significant pressure within its magma storage, the U.S. Geological Survey states.
Mount Rainier hasn't had a major eruption, with strong geologic evidence, in the past 1,000 years, Weiss-Racine said.
Greta Cross is a national trending reporter at USA TODAY. Story idea? Email her at gcross@usatoday.com.
This article originally appeared on USA TODAY: Mount Rainier experiences more than 300 earthquakes in 2 days
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