Dynamic Pulsating Eruptions

Soufriere Hill exploding -part I

Photo - Barry Voight

Recently Jon Blundy from Bristol University, England teamed up with Kathy Cashman from the University of Oregon, US to study Mount St Helens, Washington state. Together they became convinced that many of the crystals in the lavas of Mount St Helens were formed not in some large magma chamber, but as a consequence of the decrease in pressure as the magma moved up from a much greater depth. As pressure decreases magma releases its dissolved gas, rather like gas escaping when a champagne or beer bottle is opened. The loss of gas causes the magma to solidify and crystallize. Like the volcanologists working on Monserrat, Blundy and Cashman also concluded that the existence of a magma chamber beneath Mount St Helens was perhaps an illusion. During my own work on the Soufriere Hills eruptions I had also become convinced that a great deal of crystallization seen in the lavas occurred due to the loss of gas during magma ascent and that this feature might be the key to understanding the dynamics of the volcano. The escaping, bubbling gas may have caused the rising magma to turn from a mobile fluid into a strong stiff solid.

Soufriere Hill exploding - part II

Photo - Barry Voight