Over 130 small earthquakes have shaken Mount St. Helens over the past weeks, said the U.S. Geological Survey (USGS) that monitors this famous volcano in Washington State.

What makes this earthquake swarm worrisome is because the spectacular eruption of Mount St. Helens on May 18, 1980 that killed 57 persons was triggered by an earthquake.

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USGS said the quakes had a strength ranging from magnitude 0.5 to 1.3 on the Richter Scale. Quakes with a magnitude of 2.5 or less are usually not felt by humans but can be recorded by a seismograph. Over 900,000 such quakes are recorded every year around the world.

It's the quakes with a magnitude of 7.0 to 7.9, which are considered major earthquakes, that do serious damage to buildings and manmade structures. There are about 20 of these annually.

The new Mount St. Helens' earthquake swarm occurred from 1.2 to four miles beneath the surface. Seismologists, however, are more worried about the frequency of this swarm and not their magnitudes. USGS recorded a similar swarm at Mount St. Helens in 2013, 2014 and in the 1990s.

The swarms have become more common since March 14, "reaching nearly 40 located earthquakes per week," reported USGS.

USGS, however, said "there is absolutely no sign that it will erupt anytime soon, but the data we collect tells us that the volcano is still very much alive." This conclusion is based on the absence of signs that precede an eruption.

Among these telltale signs are a large increase in the amount of magma; the release of anomalous gases; shallow quakes and deformation of the crust around the volcano.

Seismologists say the volcano is "recharging" or re-pressurizing the magma or semi-molten rock stored underneath it. USGS said this recharging can continue for years without an eruption occurring.

The 1980 eruption removed over 1,000 feet from the top of Mount St. Helens. It left a huge crater and spewed hot volcanic ash and dust across the Northwest USA.

TagsMount St. Helens, earthquake, earthquake swarm, U.S. Geological Survey, Washington State, eruption