Mountains of Fire: The Nature of Volcanoes

active active volcanoes appear ashfall atmosphere avalanche basaltic began beneath blocks boiling caldera called caused cinder cloud cone continued cooling covered crater crust cubic deep deposits depth dome dust Earth Earth's surface earthquakes effect energy example explosive eruptions fall fields Figure fire formed fragments gases ground Hawaii Hawaiian heat Helens huge hundreds increase island Italy killed kilometers lake land lava flows layers less living magma major material Mauna melting meters million minerals molten Moon Mount St mountain moving mudflows nearly occur ocean particles past period Photograph plate pressure probably produced pyroclastic flows reached record ridges rift rise rock sea level side slowly solid sometimes stage steam stratosphere submarine sulfur summit surface temperature thick thousands types U.S. Geological Survey vent volcanic ash volcanic eruptions volcanoes volume weather zone