explosive eruption is a volcanic eruption of the most violent type . A notable example is the 1980 eruption of Mount St. Helens . Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent . Sometimes a lava plug will block the conduit to the summit , and when this occurs , eruptions are more violent . Explosive eruptions can send rocks , dust , gas and pyroclastic material up to into the atmosphere at a rate of up to 100,000 tonnes per second , traveling at several hundred meters per second . This cloud may then collapse , creating a fast-moving pyroclastic flow of hot volcanic matter
1980 eruption
1980 eruption of Mount St. Helens
Explosive eruption