Volcanoes

Volcanoes are sites on the surface of the planet through which gaseous, liquid and/or solid materials are expelled or erupted through the action of internal thermal processes. Volcanic eruptions produce two main types of material—lavas and pyroclastsPyroclast. Among the major features associated with them are cratersCrater and calderasCaldera, maarsMaar, lava flows and plateaux, collapse features, and laharsLahar (mudflows). Many volcanoes are associated with plate tectonics, being related to subduction zones, hot spots, etc.