VOLCANOES

Mount Fuji Mount Fuji

Mauna Loa

Volcanic Landforms Key concepts: Volcanic landforms vary with - tectonic setting, - composition of magma -------- - conditions during eruption, - volume of eruption.

Types Shield Composite Fissure Cinder

ShieldVolcanoes low viscosity basaltic lava flows. - large volcanoes with broad summit areas and low-sloping sides low viscosity basaltic lava flows. A good example of a shield volcano is the Island of Hawaii (the "Big Island").

Composite Volcanoes built by multiple eruptions, sometimes recurring over hundreds of thousands of years, sometimes over a few hundred. Andesite magma, the most common but not the only magma type, tends to form composite cones. built mostly of fragmental debris, with a structural framework of dikes and sills that knits together the voluminous accumulation of volcanic rubble.. Composite cones can grow to such heights that their slopes become unstable.

Mayon

Mount Rainier

Mount Fuji Mount Fuji

Cinder cones Cinder cones are mounds of basaltic fragments. Streaming gases carry liquid lava blombs into the atmosphere that rain back to earth around the vent to form a cone.

Calderas are circular to oblong depressions formed by collapse of the central vent during the extrusion of pyroclastic materials. Their diameters are many times larger than those of associated vents.

Domes Lava domes form by the slow extrusion of highly viscous silica-rich magma Domes can be solitary volcanoes, form in clusters, grow in craters or along the flanks of composite cones. A dome has been growing slowly within the crater of Mount St. Helens since the eruption of 1980. Domes have also filled the crater of Mt. Pelée, Martinique, etc.

List of Volcanic Hazards Pyroclastic Density Currents (pyroclastic flows and surges) Structural Collapse: Debris flow- Avalanches Dome Collapse and the formation of pyroclastic flows and surges Lava flows Tephra fall and ballistic projectiles Volcanic gas Tsunamis

Mount St Helens 1980