A cryptodome literally means "hidden dome" and refers to a lava dome which is hidden within the structure of the volcano. Most lava domes are extruded in the crater area of the volcano. If however the rising magma cannot ascend to the surface then the dome will build within the volcano causing the volcanoes slopes to bulge. The most infamous example is of Mt St Helens where a cryptodome caused the the northern slopes of the volcano to bulge. An earthquake dislodged the mountain covering the dome causing a landslide which dramatically released the pressure on the magma causing a massive lateral blast that extended for 20 miles.