There have been a series of over 130 earthquakes detected near Mount St. Helens in Washington State since March 14, 2016. These mini earthquakes are no bigger than magnitude 1.3 but indicate that the most active volcano in the Northwest is charging up.
These earthquakes are triggered when molten rocks move into Mount St. Helens’ magma chamber and is actually quite normal. What’s not as normal is the increased frequency of earthquakes but this still doesn’t indicate that the volcano will erupt anytime soon because they aren’t powerful enough to indicate that an eruption is imminent.
The USGS’ Facebook page says “There is absolutely no sign that it will erupt anytime soon…No anomalous gases, increase in ground inflation or shallow seismicity have been detected with this swarm, and there are no signs of an imminent eruption”. Volcanoes often recharge for many years before an eruption takes place.
To assure us even more that it’s not going to erupt now, the USGS said “It can take many years for a volcano to recharge between eruptive periods. We know this from factual observation at St. Helens. It last erupted in 2004-2008, prior to that 1989-2001 and 1980-1986. Notice there are pauses between eruptive periods… we are in a pause with signals that recharging is occurring.
The frequency of earthquakes have been steadily increasing since they were first detected and have reached nearly 40 per week. As noted before, the biggest was a magnitude 1.3 but that is so small that you wouldn’t even be able to feel it even if you were standing directly above the epicenter since earthquakes of 2.5 or less aren’t usually felt by humans.
In 1980, a major eruption took place that killed 57 people and blasting more than 1,300 feet off its peak and rained volcanic ash for miles around. It was triggered by a magnitude 5.1 earthquake that sent ash over 80,000 feet in the air which reached as far as 250 miles away in Spokane. It also triggered a massive collapse of the north face and was the largest known debris avalanche in recorded history.