Module 12 volcanoes

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Bahan ajar Geologi Dasar Fakultas Teknologi Mineral UPN "Veteran" Yogyakarta

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Module 12 volcanoes

  1. 1. Module 12 Volcanoes
  2. 2. The gods of volcanoes doing their task
  3. 3. VOLCANOES  A volcano is a vent or fissure in the Earth’s crust through which molten magma, hot gases, and other fluids escape to the surface of the land or to the bottom of the sea  Volcanoes may be classified broadly into:  Central Types: the products escape via a single pipe (vent)  Fissure Types: the products escape from a linear vent or crack
  4. 4. Vent positions
  5. 5. Vent positions Central Eruption Fissure Eruption Side Eruption
  6. 6. Earth’s Geotherm  GEOTHERM: increase in temperature with depth in the earth  GEOTHERMAL GRADIENT is the rate of change of T with depth  In upper 100 km, average geothermal gradient = 300C km-1  Heat source is decay of radioactive elements  This heat causes melting of rocks to form Magma
  7. 7. Composition of Magma  Variation in magma properties include:  SILICA CONTENT varies from 45% to 75%  VOLATILES (GAS CONTENT) most common gases: H2O vapor, CO2, SO2, H2S  TEMPERATURE OF ERUPTED MAGMA varies from 12000C to about 8000C  Variation in magma properties affect VISCOSITY of the magma
  8. 8. Viscosity of Magma  VISCOSITY refers to the thickness or fluidity of a liquid  Liquid with HIGH viscosity are very thick, sticky  Liquid with LOW viscosity are very fluid  Effect of various properties on magma viscosity:  Temperature: HIGH temperature = LOW viscosity (i.e. very fluid)  Silica Content: HIGH silica = HIGH viscosity  Volatile Content: HIGH volatiles = LOW viscosity (However, high gas contents contribute to explosive eruptions)
  9. 9. Types of Volcanoes
  10. 10. Types of Volcanoes
  11. 11. Shield Volcanoes
  12. 12. Shield Volcanoes
  13. 13. Shield Volcanoes
  14. 14. Shield Volcanoes
  15. 15. Shield Volcanoes
  16. 16. Shield Volcanoes
  17. 17. Shield Volcanoes HOT SPOT
  18. 18. Cinder Cone Volcanoes
  19. 19. Cinder Cone Volcanoes
  20. 20. Strato Volcanoes
  21. 21. Strato Volcanoes
  22. 22. Strato Volcanoes
  23. 23. Strato Volcanoes
  24. 24. Strato Volcanoes
  25. 25. Strato Volcanoes
  26. 26. Lava Dome Volcanoes
  27. 27. Dome Volcanoes
  28. 28. Caldera Volcanoes
  29. 29. Caldera Volcanoes The formation of Caldera
  30. 30. Eruption Types
  31. 31. Eruption Types HAWAIIAN-HAWAI
  32. 32. Eruption Types STROMBOLIAN - ANAK KRAKATAU
  33. 33. Eruption Types VULCANIAN DOME - MERAPI
  34. 34. Eruption Types VULCANIAN - SURTSEYAN
  35. 35. Eruption Types VULCANIAN - PAPANDAYAN GAMALAMA
  36. 36. Eruption Types PELEEAN - ST HELLENS
  37. 37. Eruption Types PLINIAN PINATUBO
  38. 38. Eruption Types PLINIAN - TAMBORA
  39. 39. Global Distribution of Volcanoes
  40. 40. from: http://www.geo.lsa.umich.edu/~crlb/COURSES/270 Distribution of Volcanoes Most subduction zones are in the “Ring of Fire” (so-called because of volcanism of the Pacific)
  41. 41. Volcanism & Plate Tectonics Volcanism in continental Volcanism in islands arc
  42. 42. Volcanism & Plate Tectonics Volcanism in Mid Oceanic Ridge Pacific Ocean
  43. 43. Volcanism & Plate Tectonics Hot Spot Volcanism
  44. 44. Classification of Volcanic Environment
  45. 45. Types and Zones of Volcanism
  46. 46. Finally . . . Rest in Peace COLUMNAR JOINT VOLCANIC NECK
  47. 47. Major Volcanoes of Indonesia (with eruptions since 1900 A.D.)
  48. 48. Distribution of Magmatic Arcs of Indonesia (source: Carlile & Michell, 1994)

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