At 3:00PM PDT on September 26 the US Geological Survey Cascades Volcano Observatory issued a Notice of VolcanicUnrest for Mt. St. Helens. This advisory was issued becauseof pattern of earthquakes that are consistent with movementof magma within the volcano.
A swarm of very small, shallow earthquakes that began on themorning of September 23, peaked on September 24, thensubsided on Saturday morning, and it was initially thoughtthat they might be due to rainwater seeping into hot areaswithin the volcano.
Since then, however, the swarm has change to include morethan ten large earthquakes, the most in a 24-hour periodsince the October, 1986 eruption. These quakes are of a typethat suggests the involvement of pressurized water andsteam, and possibly magma.
The USGS said that “several causes are possible, but mostpoint toward an increased probability of explosions from thelava dome if the level of current unrest continues orescalates.”
There may be much healingneeded soon.
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