what tectonic plate is mount st helens on
About Mount St. Helens. Mount St. Helens is part of the ring of fire encircling the Pacific Ocean. It was created and is continually being changed by the collision of the North American and the Juan de Fuca tectonic plates.Mount St. Helens is the youngest and most active Cascade Range volcano, born 40,000 years ago.It erupts roughly once each century.t was created and is continually being changed by the collision of the North American and the Juan de Fuca tectonic plates. Mount St. Helens is the youngest and most active Cascade Range volcano, born 40,000 years ago. It erupts roughly once each century.