classes of volcanoes


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classes of volcanoes

  1. 1. Classes of volcanoes <br />
  2. 2. Add Your Title Here<br />A volcano is a place on the Earth's surface where molten rock, gases and pyroclastic debris erupt through the earth's crust.<br />The most common perception of a volcano… <br />Volcano Classification<br /><ul><li>shape of the volcano
  3. 3. the materials they are built of
  4. 4. the way the volcanoerupts</li></li></ul><li>Stratovolcano<br />A stratovolcano is…<br />Composite volcanoes:<br />-erupt in different ways at different times<br />-built in layers<br />-quiet between eruptions<br />
  5. 5.
  6. 6. Mayon volcano, Philippines<br />Mount Shasta, California<br />Mount Shasta, California<br />Composite Volcanoes or Stratovolcanoes<br />
  7. 7. Andesite magma, tends to form composite cones.<br />-crater at the summit<br />Lava<br />-through breaks in the crater wall <br />-from fissures on the flanks of the cone<br />-8,000 feet above their bases<br />When volcanic activity ceases, erosion begins to destroy the cone.<br />
  8. 8. -cone is stripped away <br />and the hardened magma filling the conduit <br />and fissures (the dikes) become exposed<br />All that is left is the plug or "volcanic neck" and dike complex projecting above the land surface<br />
  9. 9. The Evolution of a Composite volcano<br />A. Magma, rising upward through a conduit, erupts at the Earth's surface to form a volcanic cone. Lava flows spread over the surrounding area.<br />B. As volcanic activity continues, the cone is built to a great height and lava flows form an extensive plateau around its base. <br />C. When volcanic activity ceases, erosion starts to destroy the cone. After thousands of years, the great cone is stripped away to expose the hardened "volcanic plug" in the conduit. <br />D. Continued erosion removes all traces of the cone and the land is worn down to a surface of low relief. All that remains is a projecting plug or "volcanic neck," a small lava-capped mesa, and vestiges of the once lofty volcano and its surrounding lava plateau.<br />
  10. 10. Creation<br /><ul><li>common at subduction zones, forming chains along plate tectonic boundaries where oceanic crust is drawn under continental crust or another oceanic plate</li></ul>Composite volcanoes usually erupt in an explosive way.This is usually caoused by viscous magma.<br />
  11. 11. Hazards<br />In recorded history, explosive eruptions at subduction zone volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, like Mount St. HelensandMount Pinatubo, typically erupt with explosive force.<br />Two Decade Volcanoes that erupted in 1991 provide examples of stratovolcano hazards. <br />
  12. 12. Mount Pinatubo (June 15, 1991) <br />located 90 km from Manila<br />-spewed ash 40 kilometres into the air <br />-produced huge pyroclastic flows and mudflows that devastated a large area around the volcano <br />-one of the largest eruptions in the 20th Century <br />Eruption of Mount Pinatubo was global:<br />-cooler-than-usual temperature<br />-the aerosol dispersed<br />-droplets of sulfuric acid<br />-0.5 °C<br />-affect the weather for a few years<br />
  13. 13.
  14. 14. Mount Pinatubo, Philippines<br />Composite volcano.<br />June 1991<br />
  15. 15. Unzen Volcano(island of Kyushu about 40 km east of Nagasaki) awakened from its 200-year slumber on 3 June 1991<br />-pyroclastic flow killed 43 people, including three volcanologists<br />-one of 75 active volcanoes<br />-1792, more than 15.000 people<br />
  16. 16. Unzen eruption <br />
  17. 17. Pompeii (79AD)<br />On August 24, 79AD Mount Vesuvius literally blew its top, erupting tonnes of molten ash, pumice and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.<br />
  18. 18. Pompeii (79AD)<br />Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the cities of Pompeii, Herculaneum and Stabiae suffocating the inhabitants and burying the buildings.<br />
  19. 19. Pompeii (79AD)<br />The cities remained buried and undiscovered for almost 1700 years until excavation began in 1748. These excavations continue today and provide insight into life during the Roman Empire.<br />
  20. 20. Different shapes of strato-volcanoes: <br /><ul><li>concave (like Agua),
  21. 21. pyramidal (like Stromboli)
  22. 22. convex-concave (like Vesuvius),
  23. 23. helmet-shaped (like Mount Rainier),
  24. 24. collapse caldera (like Graciosa),
  25. 25. nested (like El Piton in Teide),
  26. 26. multiple summits (like Shasta),
  27. 27. elongated along a fissure (like Hekla). </li></li></ul><li>There are many composite volcano chains on earth, notably around the Pacific rim, known as the "Rim of Fire".<br />
  28. 28. Shield volcano<br />Shield volcano<br />Some of the largest volcanoes in the world<br />products of hotspot volcanism, but can form at rift and subduction zones as well<br />The types of eruptions -Hawaiian eruptions<br />
  29. 29. 22<br />
  30. 30. Characteristics of hawaiian eruption:<br />effusive emission of fluid lavas<br />mobile nature of these lavas<br />Shield volcanoes vary widely in size with their age.<br />-often measure 5 to 6 km in diameter and surpass 460 to 610 m in height<br />-largest shield volcano (and the largest active volcano) in the world is<br />Mauna Loa in Hawaiʻi,<br />projects 4,169 m above sea level, and is over 97 km wide.<br />contain 80,000 km3 of basalt<br />
  31. 31. The Hawaiian shield volcanoes and the Galápagos islands are<br />unique. <br />-are not located near any plate boundaries; instead, the two<br />chains are fed by the movement of oceanic plates over hotspot<br />-their lavas are characterized by high levels of<br />sodium, potassium, and aluminum<br />
  32. 32. Hallmarks of shield volcanism:<br /><ul><li>rift zones</li></ul>- linear series of fissures in the volcanic edifice allows lava to be erupted from the volcano's flank instead of from its summit.<br /><ul><li>lava tubes</li></ul>-natural conduits through which lava travels<br /><ul><li>multiple splatter (or cinder) cones
  33. 33. calderas</li></ul>Valentine Cave in Lava Beds National Monument, California. This shows the classic tube shape and the curbs on the wall mark former flow levels.<br />Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii. <br />East Rift Zone on Kilauea<br />
  34. 34. Lava tube: hollow beneath a lava flow.<br />
  35. 35. Lava Tube<br />in Hawaii<br />
  36. 36. Distribution<br />Image of the sites of active and dormant shield volcanoes around the world<br />
  37. 37. Shield volcanoes are found worldwide.<br />They can form over:<br /><ul><li> hotspots (Hawaiian-Emperor seamount chain and the Galápagos Islands)
  38. 38. over rift zones(Icelandic shields and the shield volcanoes of the East Africa)
  39. 39. found in ocean basins, although they can be found in inland as well (East Africa)</li></li></ul><li>Hawaiian islands<br />-the largest shield volcano chain in the world<br /> Galápagos islands<br />-1,200 km east of Ecuador<br /> Iceland<br />-major center of shield volcanic activity <br />Pahoehoe lava flow in Hawaii.<br />
  40. 40.
  41. 41. Extraterrestrial<br />Mars' shields <br /><ul><li>27 km in height and 563 km in diameter
  42. 42. resemblance to the volcanoes of the Hawaiian Islands
  43. 43. Olympus Mons- highest known mountain in</li></ul> the solar system<br />Dangers<br />-do not pose much threat to humans <br />-they are hazardous to agriculture and infrastructure<br />-1983 eruption of Kīlauea has destroyed over 200 structures <br />and buried kilometers of highways<br />
  44. 44. Cinder conescoria cones, cinder and spatter cones<br /><ul><li>they aren't famous
  45. 45. built from lavafragments called cinders
  46. 46. grow up in groups
  47. 47. often occur on the flanks of strato volcanoes and shield volcanoes
  48. 48. grow rapidly ( 250m in height and 500m in diameter)
  49. 49. have a bowl-shaped crater at the summit. </li></ul>Most famous cinder cone-Paricutin(field in Mexico in 1943)<br /><ul><li>lava flows covered 25 km²
  50. 50. cone -424 meters
  51. 51. numerous in western North America</li></ul> cinders<br />
  52. 52. Cinder cone (230 m high) in Lassen Volcanic National Park, CA.<br />
  53. 53. Cerro Negro in Nicaragua (born in 1850)<br /><ul><li>The Earth's most historically active cinder cone
  54. 54. erupted more than 20 times</li></ul>Schematic representation of the internal structure of a typical cinder cone<br />Paricutin Volcano<br />
  55. 55.
  56. 56. Fissure vent<br />large flood basalts and lava channels<br />hard to recognize<br />crack in the ground<br />along rifts and rift zones (Iceland and the Great Rift Valley in Africa) <br />often found in shield volcanoes<br /> The Laki fissure system<br />-biggest eruption on earth in historical times<br />-during the Eldgjá eruption A.D. 934, which releas19.6 km³ of lava<br />
  57. 57. Fissure vents of Hawaiian volcanoes-“curtains of fire” <br />A volcanic fissures and lava channels<br />Fissure eruption in Iceland<br />
  58. 58. Lava dome<br />High viscosity :<br />high levels of silica in the magma<br />degassing of fluidmagma<br /> Most of the preserved domes have high silica. <br />-heights -several hundred meters <br />-grow slowly and steadily for months, years, or even<br />centuries<br />Image of the rhyoliticlava dome of Chaitén Volcano during its 2008–2009 eruption.<br />
  59. 59. Hazards<br />pyroclastic flows, destruction of property, forest fires…<br /> Characteristics <br />hemispherical dome shape<br />cycles of dome growth over long periods<br />sudden onsets of violent explosive activity <br />
  60. 60. Steep-sided lava dome, Alaska<br />
  61. 61. Subglacial volcano<br /><ul><li>pillow shapes
  62. 62. pillow breccia (a rock composed of pillow fragments) and hyaloclastite form </li></ul>The shape <br />-flattened top and steep sides. <br /><ul><li>most common in Iceland and Antarctica
  63. 63. older formations -British Columbia and Yukon Territory, Canada
  64. 64. cause jökulhlaups (great floods of water)</li></li></ul><li>the Grímsvötn Volcano beneath the Vatnajökull<br />(Iceland)(November 1996) ice sheet erupted and caused a<br />Jökulhlaup that affected more than 750 km² and destroyed<br />or severely damaged several bridges <br />Iceland’s Grimsvotn Volcano Is Erupting<br />Remnants of bridge twisted by November 5, 1996 flood following Grímsvötn eruption <br />
  65. 65. Stage 1. Early eruptions – pillow lavas and hyaloclastiteStage 2b. Formation of a subglacial moundStage 3b. Formation of a tuya<br />type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet.<br />
  66. 66. Mud volcanoGas-oil volcano<br /><ul><li>associated with subduction zones
  67. 67. 700 have been identified
  68. 68. cooler temperature
  69. 69. the largest mud volcano structures (10 kilometres in diameter and 700 metres in height)
  70. 70. 86% methane, less carbon dioxide and nitrogen
  71. 71. associated with petroleum deposits, tectonic subductionzones and orogenic belts, lava volcanoes
  72. 72. 1,100 mud volcanoes have been identified</li></li></ul><li>VolcanEl Totumo (Colombia)<br />15 m high and can accommodate 10 to 15 people on its crater<br />Volcan de Lodo El Totumo (MudVolcano), Cartagena<br />
  73. 73. Submarine volcano<br />located near areas of tectonic plate movement, known as ocean ridges<br />exist in shallow water<br />There are three circumstances where tectonic<br />plates can interact with each other and the Earth's<br />molten interior to form submarine volcanoes. <br />tectonic plate slides over a "hot spot" <br />where tectonic plates are spreading apart at the mid-ocean ridges<br />subduction<br />
  74. 74. Pillowed Lava Flow<br /><ul><li>lava flow that formed under water
  75. 75. interaction of water with the molten lava forms a thick glassy crust around the flowing lava</li></li></ul><li>Scientists still have much to learn about the location and activity of underwater volcanoes.<br />The Kolumbo underwater volcano (Aegean Sea) was discovered in 1650 when it burst from the sea and erupted, killing 70 people on the nearby island of Santorini.<br /><ul><li>seamounts
  76. 76. formed from extinct volcanoes, rising from a seafloor of 1,000 - 4,000 meters depth.
  77. 77. 30,000 seamounts occur across the globe, with only a few </li></ul> having been studied<br />
  78. 78. Supervolcano<br />magma rises into the crust from a hotspotbut is unable to break through the crust<br />pressure builds in a large and growing magma pool until the crust is unable to contain the pressure<br />form at convergent plate boundaries and continental hotspot locations<br />rate VEI 8 -"super eruptions“ <br />colossal events that throw out at least 1,000 km3Dense Rock Equivalent (DRE) of ejecta<br />
  79. 79.
  80. 80.
  81. 81. rases virtually all life in a radius of hundreds of kilometers from the site, and entire continental regions further out can be buried meters deep in ash<br />Form circular calderas<br />remain for millions of years after all volcanic activity at the site has died<br />every 50,000 years the Earth experiences a super-volcano<br />
  82. 82. 1,000 sq km of land obliterated by pyroclastic ash flows, the surrounding continent is coated in ash and sulphur gases are injected into the atmosphere<br />Taupo in New Zealand,mostrecent super-volcano, around 26,500 years ago<br />the most damaging super-volcano in human history was Toba, on Sumatra, Indonesia, 74,000 years ago<br /> -close to the equator <br />-temperatures were dramatically reduced <br />
  83. 83. Volcano Types<br />