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STRUCTURES DUE TO VOLCANISM

STRUCTURES DUE TO VOLCANISM. INTRUSIVE AND EXTRUSIVE VOLCANIC LANDFORMS. VOLCANISM :.

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STRUCTURES DUE TO VOLCANISM

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  1. STRUCTURES DUE TO VOLCANISM INTRUSIVE AND EXTRUSIVE VOLCANIC LANDFORMS

  2. VOLCANISM: • Defined as the transfer of magma from one area of the earth to another, due to a change in the pressure of the earth. It is the drop in pressure that allows the semi-liquid molten rock to become liquid and rise to the top.

  3. EXTRUSIVE FORMS • When magma reaches the surface of the earth. • Extrusive forms have been exposed by erosion or released in the form of lava. • The volcanic shape (cone) is considered an extrusive feature.

  4. PARTS OF A VOLCANO • A cone or crater at the top. • When the cone walls break away, the basin which is left over is a caldera. • Sometimes, this is filled with water and is called a crater lake.

  5. Calderas • range in shape from circular to oblong. These depressions are formed by collapse of the central vent during the extrusion of pyroclastic materials. • Their diameters are many times larger than those of associated vents.

  6. CONE OR CRATER: Wizard Is. OR

  7. CALDERA

  8. 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.

  9. TYPES OF VOLCANOES • The type of volcano is dependent upon what type of plate boundary it is at and what type of magma is extruded • There are 3 types: cinder, shield, and composite volcanoes.

  10. CINDER CONE • Mainly acidic or SIALIC magma is extruded. The rock cools quickly in the form of cinder and ash. This results in steep sides and a narrow neck. This volcano can become plugged easily and thus is explosive in nature.

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

  12. CINDER CONE

  13. CINDER CONE: Diamond Head

  14. CINDER CONE: ARIZONA

  15. Cinder Cone: Pu`u ka Pele – Maui

  16. SHIELD CONE • Mainly basic or SIMATIC magma is extruded. The rock cools very slowly and forms low cones and wide sheets of lava. Free flows and slow cooling means low explosiveness.

  17. Shield Volcanoes • - large volcanoes with broad summit areas and low-sloping sides • low viscosity basaltic lava flows.

  18. SHIELD CONE

  19. SHIELD CONE: Mauna Kea Hawaii

  20. SHIELD CONE: Haleakala10000 ft above, 18000 ft below

  21. Gabi Laske – Iceland

  22. COMPOSITE CONE • Formed by the mixture of SIALIC AND SIMATIC magma. This builds up alternate layers of cinder ash and lava. As a result, both great width and height are attained, making the world’s largest volcanoes. • Most common in oceanic-continental subduction zones, where there is a mixture of simatic and sialic rock

  23. Composite Continued • Also known as – Strato Volcanoes • built by multiple eruptions, sometimes recurring over hundreds of thousands of years, sometimes over a few hundred.

  24. COMPOSITE CONE

  25. COMPOSITE CONE: Mt Fuji

  26. COMPOSITE CONE: Mt. Rainier

  27. Mount Rainier

  28. COMPOSITE CONE:Mt. St Helens

  29. MT ST HELENS MAY 18, 1980

  30. MT ST HELENS MAY 18, 1980

  31. BEFORE:

  32. AFTER:

  33. VOLCANO CLASSIFICATION • Active means they show signs of movement and unrest • Dormant shows possibilities of future unrest • Extinct show no signs of any activity

  34. DESTRUCTIVE EFFECTS: • Lava flow and explosive rock can destroy surrounding countrysides. • Cinder ash can bury surrounding areas and affect weather patterns worldwide • Tidal waves (tsunamis) can result • Nuee ardentes, clouds of super-heated steam and gas can blow down the mountain destroying all in its path.

  35. 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 LAVA FLOW

  36. CINDER ASH and MUDFLOW (lahar)

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