Small earthquakes are shaking the dormant Mount St. Helens

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Small Earthquakes Are Shaking The Dormant Mount St. Helens

Mount St. Helens -- dormant since 2008 -- seems to be rumbling. The U.S. Geological Survey says more than 130 small earthquakes have been detected under the volcano in the past eight weeks.

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None of the earthquakes have been very big -- the largest was a 1.3 on the Richter scale -- and they've all been at least a mile below the surface, meaning people probably didn't feel them.

FLASHBACK: Mount St. Helens through time

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Mount St. Helens' eruption 35 years ago
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Small earthquakes are shaking the dormant Mount St. Helens
An eruption column rises from Mount St. Helens, Washington, 22nd July 1980. This was one of a series of explosive eruptions by the volcano in 1980, the most destructve occurring on 18th May and causing the entire north face (nearest camera) to slide away. In the background (right) is the stratovolcano Mount Hood, Oregon. (Photo by Max Gutierrez/Bride Lane Library/Popperfoto/Getty Images)
360998 18: A helicopter hovers over a cloud of ash May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 20: Ash covers a pickup truck May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 21: A cloud of ash covers a mountaintop May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 17: Ash covers the landscape May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 14: A cloud of ash covers a mountaintop May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 10: Ash covers a pickup truck May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 30: Ash and mud surrounds trees May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 28: A cloud of ash covers landscape May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 08: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 11: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 04: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 12: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360998 29: A mudslide covers a road May 23, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 05: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
360995 03: A cloud of ash covers a mountaintop May 22, 1980 in Washington State. On May 18, 1980, an earthquake caused a landslide on Mount St. Helens'' north face, taking off the top of the mountain and triggering an eruption that killed 57 people, wiped out river valleys and destroyed enough trees to build 300,000 homes. (Photo by John Barr/Liaison)
In 1980, a major volcanic eruption occurred at Mount St Helens, a volcano located in state of Washington, in the United States. (Photo by: Universal History Archive/UIG via Getty images)
True colour satellite image of Mount St-Helens, an active vulcanoe (2250m high) in Washington State, US. Image taken on 29 July 1972, before its catastrophic eruption of 1980, using LANDSAT data., Mount St Helens, Washington State, Us, In 1972, True Colour Satellite Image (Photo by Planet Observer/Universal Images Group via Getty Images)
In 1980, a major volcanic eruption occurred at Mount St Helens, a volcano located in state of Washington, in the United States. (Photo by: Universal History Archive/UIG via Getty images)
Golden shovels are shown Tuesday, May 18, 2010, near Mount St. Helens, prior to the ground-breaking for a new outdoor amphitheater at the Johnston Ridge Observatory, on the 30th anniversary of the volcano's violent May 18, 1980 eruption in Washington state. (AP Photo/Ted S. Warren)
**ADVANCE FOR WEEKEND, MAY 14-15 ** Crosses commemorating Ed and Eleanor Murphy, who were killed in the massive Mount St. Helens eruption nearly 25 years ago, are decorated with flowers as they stand in the forest approximately 11 miles west of the active volcano in Washington state, May 5, 2005. Of the 57 people known to have lost their lives on the mountain May 18, 1980, only three are known to have been killed within the "red zone," the area cordoned off by officials in the weeks leading up to the eruption. (AP Photo/Don Ryan)
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But for those who study volcanoes, this swarm of activity indicates Mount St. Helens is recharging. In other words, new magma is refilling the volcano's chamber.

In 1980, an explosive eruption blew the top off the mountain, killing 57 people, and the hot ash sparked forest fires.

A repeat of that isn't likely this time. In fact, there were larger earthquake swarms in the early and late 1990s, which didn't lead to anything severe. There are also none of the usual indications of imminent eruptions like irregular gas release or ground inflation.

And the last time Mount St. Helens erupted in 2004, it wasn't nearly as violent. The USGS says it can take years for magma recharge to reach a point that it causes an eruption.

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