Mount St. Helens was an active stratovolcano located in the state of Washington. It was known for its famous by its Eruption in 1980. It last erupted in 2008.
During the 2012 apocalypse, the volcano presumably entered in an eruption, destroying the entire state of Washington, engulfing it under volcanic ash, as the other volcanoes, Mount Adams also erupted in the area. Mount St Helens was then swept by a megatsunami during the Worldwide Flooding.
As a result of the apocalypse, Mount St Helens went back to a dormant status, but like Washington, it is currently submerged underwater.