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<ul><li>Volcano :  </li></ul><ul><li>an  opening  in the earth’s surface through which lava, hot gases, and rock fragments...
<ul><ul><li>Magma  50-100  miles below the earth’s surface slowly begins to  rise  to the surface </li></ul></ul><ul><ul><...
<ul><ul><li>Pressure  from the surrounding rock causes the magma to  blast  or  melt  a conduit (channel) to the surface w...
<ul><ul><li>The magma, now called lava,  builds  up at the  vent  forming a volcano </li></ul></ul>How do they form?
<ul><ul><li>Often the volcano sides will be higher than the vent forming a depression called a  crater </li></ul></ul>How ...
<ul><li>Crater :  </li></ul>
<ul><li>Caldera:   </li></ul><ul><li>an unusually large crater or the remains when the cone collapses into its own magma c...
Anatomy of a Volcano <ul><li>Cone :  </li></ul><ul><li>the  above  ground structure built from  lava and/or tephra </li></ul>
<ul><li>Conduit :  </li></ul><ul><li>the path that magma takes from the  magma chamber  to the  vent </li></ul>
<ul><li>Magma Chamber :  </li></ul><ul><li>the reservoir located under the volcano where  magma collects  and becomes the ...
<ul><li>Lava:  </li></ul><ul><li>molten,  liquid  rock on the surface of the earth </li></ul>
<ul><li>Parasitic Cone:  </li></ul><ul><li>a smaller secondary volcano built on the side of or near the main volcano, but ...
<ul><li>Fumarole:  </li></ul><ul><li>a secondary vent that emits only  gases </li></ul>
<ul><li>Fissure :  </li></ul><ul><li>a long fissure ( crack ) from which lava flows </li></ul>
<ul><li>Vent :  opening  of the volcano, through which lava, ash and gases flow </li></ul>
What comes out of volcanoes? <ul><li>Lava </li></ul><ul><li>Tephra </li></ul><ul><li>Gases </li></ul>
<ul><li>Lava— 3 kinds: </li></ul>
<ul><li>Pahoehoe lava:  </li></ul><ul><li>Hot, thin, fast flowing  </li></ul><ul><li>harden with a relatively smooth surfa...
<ul><li>Pahoehoe lava:  </li></ul>
<ul><li>Aa lava:  </li></ul><ul><li>Cooler,  thicker , slow moving </li></ul><ul><li>Hardens with a rough, jagged, sharp e...
<ul><ul><li>Pillow Lava:  </li></ul></ul><ul><ul><li>Lava suddenly cooled by  water </li></ul></ul><ul><ul><li>shows sack-...
Tephra <ul><li>Basically,  rock  fragments </li></ul><ul><li>Also known as  pyroclastic  rock fragments. </li></ul><ul><li...
Ash & dust
Volcanic Bombs This dacite breadcrust bomb (about 15 cm in diameter) was erupted from the lava dome at Mount St. Helens, W...
<ul><li>Lahar (mudflow):   </li></ul><ul><li>mixture of  ash, eroded land , and water flowing down river valleys </li></ul>
<ul><li>Lahar (mudflow):   </li></ul>
GASES <ul><li>water vapor,  carbon dioxide , nitrogen,  sulfur dioxide , hydrogen sulfide,  chlorine </li></ul>
Where do Volcanoes Occur?
Where do Volcanoes Occur? location Examples Divergent Boundaries :  where plates move  APART Iceland
Where do Volcanoes Occur? location Examples convergent Boundaries :  where plates  come together Cascade range volcanoes, ...
<ul><li>Cascade Volcanoes </li></ul>
Where do Volcanoes Occur? location Examples Hot Spots :  plates riding over an especially hot place in the mantle   Hawaii...
Hot Spots
<ul><ul><li>Two factors determine the type of eruption :  </li></ul></ul><ul><ul><li>Amount of  water vapor  & other  gase...
<ul><ul><li>Trapped gases under  high  pressure will violently explode when the magma reaches the  lower  pressure of the ...
<ul><ul><li>Has  granitic  magma is very  thick  and  plugs  the vent causing the pressure to build until it blows violent...
<ul><ul><li>The  high  water content of the magma produces more water vapor which when mixed in granitic magma produces ex...
<ul><ul><li>Low pressure gas </li></ul></ul>Quiet Eruptions
<ul><ul><li>Has  basaltic  magma (is more fluid and will flow instead of explode) </li></ul></ul>Quiet Eruptions
<ul><ul><li>… and has low  water  content </li></ul></ul><ul><ul><li>Examples : Hawaii </li></ul></ul>Quiet Eruptions
Cinder cones <ul><li>Small base,  steep-sided, loosely consolidated </li></ul><ul><li>Up to 1000 feet tall </li></ul><ul><...
 
<ul><ul><li>Cinder Cones :  </li></ul></ul>Cinder Cones
Shield volcanoes <ul><li>Large base,  gentle slope , lava rock layers </li></ul><ul><li>A few  miles  high </li></ul><ul><...
Shield volcano on Mars; Taken from space Take a look at these examples: http://www.volcano.si.edu/world/tpgallery.cfm?cate...
<ul><li>Shield Volcanoes   </li></ul>Mauna Kea Shield volcanoes
Composite or strato <ul><ul><li>Large mountain volcano often  snow capped , a few miles high </li></ul></ul><ul><ul><li>Li...
Composite or strato <ul><ul><li>Have alternating eruptions of  tephra  (air-borne) and  lava .  The tephra adds  height  t...
STrato/Composite Llaima Volcano, Chile.
<ul><ul><li>Composite (strato) Volcanoes examples:  </li></ul></ul>Mt. Rainier Mt. Fuji Mt. Kilimanjaro
Composite/strato volcanoes
<ul><ul><li>Active (awake):  </li></ul></ul><ul><ul><li>Has erupted within recent time and can erupt again at  any time . ...
Mt St. Helens
<ul><li>Dormant (sleeping):  </li></ul><ul><li>No  eruption within recent times, but there is record of past eruptions  </...
<ul><li>Extinct:  </li></ul><ul><li>No eruption within recorded history </li></ul><ul><li>Not expected to  ever erupt agai...
Crater Lake
<ul><li>Mount Rainier </li></ul><ul><ul><li>The most  dangerous  volcano in the US </li></ul></ul><ul><ul><li>The danger i...
<ul><li>Mount Rainier </li></ul><ul><ul><li>The mountain is dangerously  unstable , a tall, steep heap of loose rock held ...
 
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Volcanoes2009

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Transcript of "Volcanoes2009"

  1. 2. <ul><li>Volcano : </li></ul><ul><li>an opening in the earth’s surface through which lava, hot gases, and rock fragments erupt </li></ul>Introduction to volcanoes
  2. 3. <ul><ul><li>Magma 50-100 miles below the earth’s surface slowly begins to rise to the surface </li></ul></ul><ul><ul><li>As the magma rises it melts gaps in the surrounding rock </li></ul></ul><ul><ul><li>As more magma rises a large reservoir forms as close as 2 miles below the surface (magma chamber) </li></ul></ul>How do they form?
  3. 4. <ul><ul><li>Pressure from the surrounding rock causes the magma to blast or melt a conduit (channel) to the surface where magma erupts onto the surface through a vent (opening) </li></ul></ul>How do they form?
  4. 5. <ul><ul><li>The magma, now called lava, builds up at the vent forming a volcano </li></ul></ul>How do they form?
  5. 6. <ul><ul><li>Often the volcano sides will be higher than the vent forming a depression called a crater </li></ul></ul>How do they Form?
  6. 7. <ul><li>Crater : </li></ul>
  7. 8. <ul><li>Caldera: </li></ul><ul><li>an unusually large crater or the remains when the cone collapses into its own magma chamber </li></ul>
  8. 9. Anatomy of a Volcano <ul><li>Cone : </li></ul><ul><li>the above ground structure built from lava and/or tephra </li></ul>
  9. 10. <ul><li>Conduit : </li></ul><ul><li>the path that magma takes from the magma chamber to the vent </li></ul>
  10. 11. <ul><li>Magma Chamber : </li></ul><ul><li>the reservoir located under the volcano where magma collects and becomes the supply of magma/lava to build the volcano </li></ul>
  11. 12. <ul><li>Lava: </li></ul><ul><li>molten, liquid rock on the surface of the earth </li></ul>
  12. 13. <ul><li>Parasitic Cone: </li></ul><ul><li>a smaller secondary volcano built on the side of or near the main volcano, but sharing the same conduit to the magma chamber </li></ul>
  13. 14. <ul><li>Fumarole: </li></ul><ul><li>a secondary vent that emits only gases </li></ul>
  14. 15. <ul><li>Fissure : </li></ul><ul><li>a long fissure ( crack ) from which lava flows </li></ul>
  15. 16. <ul><li>Vent : opening of the volcano, through which lava, ash and gases flow </li></ul>
  16. 17. What comes out of volcanoes? <ul><li>Lava </li></ul><ul><li>Tephra </li></ul><ul><li>Gases </li></ul>
  17. 18. <ul><li>Lava— 3 kinds: </li></ul>
  18. 19. <ul><li>Pahoehoe lava: </li></ul><ul><li>Hot, thin, fast flowing </li></ul><ul><li>harden with a relatively smooth surface </li></ul><ul><li>Often has a ropy or wrinkled appearance </li></ul>
  19. 20. <ul><li>Pahoehoe lava: </li></ul>
  20. 21. <ul><li>Aa lava: </li></ul><ul><li>Cooler, thicker , slow moving </li></ul><ul><li>Hardens with a rough, jagged, sharp edge surface </li></ul>
  21. 22. <ul><ul><li>Pillow Lava: </li></ul></ul><ul><ul><li>Lava suddenly cooled by water </li></ul></ul><ul><ul><li>shows sack-like segments (stuffed pillows) </li></ul></ul>
  22. 23. Tephra <ul><li>Basically, rock fragments </li></ul><ul><li>Also known as pyroclastic rock fragments. </li></ul><ul><li>There are many different possible sizes, from very small (volcanic ash or dust to much larger rocks (called volcanic bombs ) </li></ul>
  23. 24. Ash & dust
  24. 25. Volcanic Bombs This dacite breadcrust bomb (about 15 cm in diameter) was erupted from the lava dome at Mount St. Helens, Washington.
  25. 26. <ul><li>Lahar (mudflow): </li></ul><ul><li>mixture of ash, eroded land , and water flowing down river valleys </li></ul>
  26. 27. <ul><li>Lahar (mudflow): </li></ul>
  27. 28. GASES <ul><li>water vapor, carbon dioxide , nitrogen, sulfur dioxide , hydrogen sulfide, chlorine </li></ul>
  28. 29. Where do Volcanoes Occur?
  29. 30. Where do Volcanoes Occur? location Examples Divergent Boundaries : where plates move APART Iceland
  30. 31. Where do Volcanoes Occur? location Examples convergent Boundaries : where plates come together Cascade range volcanoes, Andes
  31. 32. <ul><li>Cascade Volcanoes </li></ul>
  32. 33. Where do Volcanoes Occur? location Examples Hot Spots : plates riding over an especially hot place in the mantle Hawaii, Yellowstone, Iceland
  33. 34. Hot Spots
  34. 35. <ul><ul><li>Two factors determine the type of eruption : </li></ul></ul><ul><ul><li>Amount of water vapor & other gases in the magma </li></ul></ul><ul><ul><li>The chemical composition of the magma </li></ul></ul>Types of Volcanic Eruptions
  35. 36. <ul><ul><li>Trapped gases under high pressure will violently explode when the magma reaches the lower pressure of the surface. </li></ul></ul>Explosive Eruptions
  36. 37. <ul><ul><li>Has granitic magma is very thick and plugs the vent causing the pressure to build until it blows violently out the vent </li></ul></ul>Explosive Eruptions Mt. St. Helens
  37. 38. <ul><ul><li>The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions </li></ul></ul>Explosive Eruptions Mont serrat
  38. 39. <ul><ul><li>Low pressure gas </li></ul></ul>Quiet Eruptions
  39. 40. <ul><ul><li>Has basaltic magma (is more fluid and will flow instead of explode) </li></ul></ul>Quiet Eruptions
  40. 41. <ul><ul><li>… and has low water content </li></ul></ul><ul><ul><li>Examples : Hawaii </li></ul></ul>Quiet Eruptions
  41. 42. Cinder cones <ul><li>Small base, steep-sided, loosely consolidated </li></ul><ul><li>Up to 1000 feet tall </li></ul><ul><li>Life span of a few years </li></ul><ul><li>Commonly built from gravel size lava rock fragments called cinders </li></ul><ul><li>Violent eruptions, dangerous when close---High pressure gas bubbles causes thick lava to explode into the air, lava begins to cool as it rises and falls becoming very sticky </li></ul><ul><li>When lava hits the ground it sticks rather than flows </li></ul><ul><li>This builds a steep cone with a small base </li></ul>
  42. 44. <ul><ul><li>Cinder Cones : </li></ul></ul>Cinder Cones
  43. 45. Shield volcanoes <ul><li>Large base, gentle slope , lava rock layers </li></ul><ul><li>A few miles high </li></ul><ul><li>Life span of a million years or more </li></ul><ul><li>The lava is hot, thin, very fluid often basaltic </li></ul><ul><li>Example: Hawaiian Islands, Iceland </li></ul>
  44. 46. Shield volcano on Mars; Taken from space Take a look at these examples: http://www.volcano.si.edu/world/tpgallery.cfm?category=Shield%20Volcanoes The Mauna Loa volcano in Hawaii—the largest volcano on Earth—has the broad expanse characteristic of shield volcanoes. It spreads across half the island of Hawaii.
  45. 47. <ul><li>Shield Volcanoes </li></ul>Mauna Kea Shield volcanoes
  46. 48. Composite or strato <ul><ul><li>Large mountain volcano often snow capped , a few miles high </li></ul></ul><ul><ul><li>Life span of million years or more </li></ul></ul>
  47. 49. Composite or strato <ul><ul><li>Have alternating eruptions of tephra (air-borne) and lava . The tephra adds height to the volcano and the lava cements the tephra together and adds to the base . </li></ul></ul><ul><ul><li>Found mostly in subduction zones and have violent eruptions. </li></ul></ul>
  48. 50. STrato/Composite Llaima Volcano, Chile.
  49. 51. <ul><ul><li>Composite (strato) Volcanoes examples: </li></ul></ul>Mt. Rainier Mt. Fuji Mt. Kilimanjaro
  50. 52. Composite/strato volcanoes
  51. 53. <ul><ul><li>Active (awake): </li></ul></ul><ul><ul><li>Has erupted within recent time and can erupt again at any time . </li></ul></ul><ul><ul><li>Pre-eruption activities : </li></ul></ul><ul><ul><ul><li>Increase in earthquake activity under the cone </li></ul></ul></ul><ul><ul><ul><li>increase in temperature of cone, </li></ul></ul></ul><ul><ul><ul><li>melting of ice/snow in the crater </li></ul></ul></ul><ul><ul><ul><li>swelling of the cone </li></ul></ul></ul><ul><ul><ul><li>steam eruptions </li></ul></ul></ul><ul><ul><ul><li>minor ash eruptions </li></ul></ul></ul>Volcano Activity Levels (Stages)
  52. 54. Mt St. Helens
  53. 55. <ul><li>Dormant (sleeping): </li></ul><ul><li>No eruption within recent times, but there is record of past eruptions </li></ul><ul><li>Can become active and erupt again after a “wake up” period </li></ul><ul><li>Example : Mt. Rainier </li></ul>
  54. 56. <ul><li>Extinct: </li></ul><ul><li>No eruption within recorded history </li></ul><ul><li>Not expected to ever erupt again </li></ul><ul><li>Example: Mount Mazama (Crater Lake) </li></ul>
  55. 57. Crater Lake
  56. 58. <ul><li>Mount Rainier </li></ul><ul><ul><li>The most dangerous volcano in the US </li></ul></ul><ul><ul><li>The danger is mostly from lahars traveling down river valleys at a speed of 25mph and destroying everything in its path </li></ul></ul><ul><ul><li>100,000 people live on the solidified mudflows of previous eruptions </li></ul></ul>
  57. 59. <ul><li>Mount Rainier </li></ul><ul><ul><li>The mountain is dangerously unstable , a tall, steep heap of loose rock held together by the force of gravity and a cubic mile of glacier ice that could be melted or shaken loose </li></ul></ul><ul><ul><li>Lahar flows average every 500 years and have gone as far as the Puget Sound lowlands </li></ul></ul><ul><ul><li>Mount Rainier has erupted 4 times in the last 4000 years with the last eruption 200 years ago </li></ul></ul>
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