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- 1. Module 12 Volcanoes
- 2. The gods of volcanoes doing their task
- 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. Vent positions
- 5. Vent positions Central Eruption Fissure Eruption Side Eruption
- 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. 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. 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. Types of Volcanoes
- 10. Types of Volcanoes
- 11. Shield Volcanoes
- 12. Shield Volcanoes
- 13. Shield Volcanoes
- 14. Shield Volcanoes
- 15. Shield Volcanoes
- 16. Shield Volcanoes
- 17. Shield Volcanoes HOT SPOT
- 18. Cinder Cone Volcanoes
- 19. Cinder Cone Volcanoes
- 20. Strato Volcanoes
- 21. Strato Volcanoes
- 22. Strato Volcanoes
- 23. Strato Volcanoes
- 24. Strato Volcanoes
- 25. Strato Volcanoes
- 26. Lava Dome Volcanoes
- 27. Dome Volcanoes
- 28. Caldera Volcanoes
- 29. Caldera Volcanoes The formation of Caldera
- 30. Eruption Types
- 31. Eruption Types HAWAIIAN-HAWAI
- 32. Eruption Types STROMBOLIAN - ANAK KRAKATAU
- 33. Eruption Types VULCANIAN DOME - MERAPI
- 34. Eruption Types VULCANIAN - SURTSEYAN
- 35. Eruption Types VULCANIAN - PAPANDAYAN GAMALAMA
- 36. Eruption Types PELEEAN - ST HELLENS
- 37. Eruption Types PLINIAN PINATUBO
- 38. Eruption Types PLINIAN - TAMBORA
- 39. Global Distribution of Volcanoes
- 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. Volcanism & Plate Tectonics Volcanism in continental Volcanism in islands arc
- 42. Volcanism & Plate Tectonics Volcanism in Mid Oceanic Ridge Pacific Ocean
- 43. Volcanism & Plate Tectonics Hot Spot Volcanism
- 44. Classification of Volcanic Environment
- 45. Types and Zones of Volcanism
- 46. Finally . . . Rest in Peace COLUMNAR JOINT VOLCANIC NECK
- 47. Major Volcanoes of Indonesia (with eruptions since 1900 A.D.)
- 48. Distribution of Magmatic Arcs of Indonesia (source: Carlile & Michell, 1994)
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