Mount St Helens Is Rumbling Again, So Should We Be Worried?

Peering at the peak through the nearby observatory deck. Daniel W. Slocum/Shutterstock

As has been reported by the United States Geological Survey (USGS), Mount St Helens is rumbling again, with swarms of earthquakes beneath the surface appearing to suggest that magma is moving around down there. Don’t panic though – this happens more than you think, and besides, if you’re worried about this, then you’re focusing on the wrong volcano.

Just recently, some particularly heavy snowfall caused the famous volcano’s monitoring equipment to fail for a while. Bad weather delayed repairs, but at the end of April, technicians managed to get everything online again. Immediately, the equipment started registering small and very frequent seismic tremors beneath the surface.

Between April 21 and May 5, there were about 47 quakes registered, but it’s likely that there were around 100 in total. They are fairly shallow, ranging from surface-level shakes to those 2-7 kilometers (1.2-4.3 miles) beneath the ground, and they’re all of a similar, albeit low (<1.3M) magnitude. This suggests that magma is moving around in the volcano’s complex plumbing system.

Beyond that, however, there’s little that can be inferred from this data. There’s no indication that an eruption is imminent – the ground isn’t deforming, and volatile gases aren’t being emitted at the summit. Groundwater isn’t getting hotter or showing drastically altered chemistry.

These types of low-level swarms have been taking place since at least 2008. This long-term pattern suggests that the magma chambers beneath Mount St Helens are recharging.

If this sounds scary, then let me assuage your nerves. It’s good to remember that there are thousands of dormant volcanoes around the world that are recharging in this manner, and explosive-style stratovolcanoes tend to take a few hundred years to build up to something paroxysmal.

Mount St Helens last blew its top in a catastrophic manner back in May 1980. It was so powerful that the magma burst out the side of the volcano rather than just the top, which demolished much of the “original” mountain. This event released plenty of pent-up pressure and emptied its bizarrely arranged magma caches, which means that it’ll be some time before another major eruption will take place.

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There will be minor eruptions in the near future, but nothing anyone should worry about. Matthew Connolly/Shutterstock

You should be more worried about the other volcanoes nearby, many of which are poorly monitored. Mount Rainier up near Seattle, for example, hasn’t properly erupted in 5,000 years, which means something significant is on its way. There are 3.7 million people living nearby that are at risk of such a future eruption.

It’s worth pointing out that the President was keen to defund the USGS and its volcano monitoring capabilities, but Congress, fortunately, refused to comply. If you want to know whether a volcano in the US – including Mount St Helens – is going to kill you, you should probably give volcanologists their funding, don’t you think?

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