Slide 1

VOLCANOES Slide 2 Slide 3 Mount Fuji Slide 4 Mauna Loa Slide 5 Volcanic Landforms Key concepts: Volcanic landforms vary with - tectonic setting, - composition of magma -------- - conditions during eruption, - volume of eruption. Slide 6 Types Shield Composite Fissure Cinder Slide 7 Slide 8 ShieldVolcanoes - 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"). Slide 9 Slide 10 Slide 11 Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 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. Slide 17 Mayon Slide 18 Slide 19 Slide 20 Slide 21 Slide 22 Mount Rainier Slide 23 Slide 24 Slide 25 Mount Fuji Slide 26 Slide 27 Slide 28 Slide 29 Slide 30 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. Slide 31 Slide 32 Slide 33 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. Slide 34 Slide 35 Slide 36 Slide 37 Slide 38 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. Pele, Martinique, etc.Mount St. Helens Slide 39 Slide 40 Slide 41 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 Slide 42 Slide 43 Mount St Helens 1980