Those of you who are about my age will remember back in 1980, when Mount St Helens erupted through vast amounts of ash into the air and lava down the sides of it’s slopes. That eruption ripped 1300 feet off the top of the mountain and led to the death of 57 people. The ash was so thick and voluminous that the city of Spokane, Washington was blacked out.
The eruption was triggered by an earthquake measuring 5+. Instruments now show that there are earthquakes under Mount St Helens every two hours or so but none yet larger than 1.3 in magnitude. Scientists say there is no need to panic yet and that it could be a while before it erupts again, but erupt it will.
Scientists with the Cascades Volcano Observatory (CVO) and the Pacific Northwest Seismic Network (PNSN) first detected the earthquakes on April 21, according to the USGS.
Deep snow this past winter left the monitoring sites buried, and knocked out telemetry and power.
But, once everything had been restored to nearly full capacity, the network immediately began picking up signs of small earthquakes at a rate of one quake every few hours.
The scientists have found ‘good evidence’ to suggest this swarm began as early as April 16, and was definitely underway by the 18th.
The largest so far was a magnitude 1.3, and most have occurred between sea level and 3 mi (5 km) below sea level (approximately 2-7 km below the surface), according to USGS.
The earthquakes detected this year at Mount St Helens are thought to be tied to the recharge in the magmatic system, which was first detected in 2008.
And, the activity mirrors swarms that occurred this past November and almost exactly a year ago in March-May, which brought low-magnitude earthquakes at a rate of about 1-2 quakes per hour.
Still, the researchers say the current activity does not indicate that the volcano is readying for another deadly eruption anytime soon.