Week 5 - Converging plates

Shortly after visiting Mount St. Helens in Washington state, I decided to learn more about the forces producing these phenomena. So, we kept driving and admiring the adjacent area until reaching the coast. Here at the coast is where the Juan de Fuca plate meets the North American plate.

The above illustration shows the convergent boundaries of the oceanic plate Juan de Fuca and the continental North American plate. The converging of these two plates creates a subduction zone as the oceanic plate moves under the continental plate. As the plate sinks deeper into the earth, water is released and rises into the overlying mantle lowering its melting temperature of the mantle rock to the point of actual melting. Eventually the magma create by the melting mantle rock, rises and continues to rise until reaching earth surface as a volcanic eruption.

All the compressional stresses produced at the convergent boundary created the volcanic mountain I visited earlier in my trip. It created what is call a volcanic arc, in this case the Cascade Volcanic Arc. Folding and faulting of rocks happen on convergent boundaries,           but folding is more evident on this structural style.

   Before departing I learned that earthquakes called megathrust occur at subduction zones.    There is speculation of one happening soon. Let us hope we are wrong about that one.