Mount St Helens

4 Nov 2016

   At ... geologists have been trying to understand how Mount St Helens works. It is a volcano of the Cascade Arc and one of a string of eruptive volcanoes that run parallel to the hypothetical subduction zone between tow major plates between British Columbia and California. Most of the volcanoes are thought to lie along the line of the plate boundary - but now they think that Mount St Helens might be somewhat offset. In  2014 thousands of sensors were deployed to measure what was going on inside the ground. They then drilled a series of holes and packed them with explosives in order to find out if they could trigger some seismic signals - but al they got was some very minor earthquakes. Instead of a magma chamber beneath Mount St Helens there is serpentine rock. So how did Mount St Helens get is magma? Is there really a subducting plate?