Volcano Notes


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Description of volcanoes

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  • Volcano Notes

    1. 1. Volcano Notes
    2. 2. Individual Volcanoes - Locations <ul><li>Subduction Zones: </li></ul><ul><ul><li>Association between volcanoes & subduction zones. </li></ul></ul><ul><ul><li>Ring of Fire = Ring of Subduction Zones </li></ul></ul><ul><li>Continental Rift Zone: </li></ul><ul><ul><li>A few volcanoes are associated with rift zones. </li></ul></ul><ul><ul><li>e.g. Kilimanjaro & others in east African rift. </li></ul></ul><ul><li>Hot Spots: </li></ul><ul><ul><li>Some coincide with plate boundaries, most don’t. </li></ul></ul><ul><ul><li>e.g. Hawaii </li></ul></ul><ul><ul><li>Galapagos Is., Iceland, Yellowstone. </li></ul></ul>
    3. 3. Where are volcanoes located? Is there a pattern? AT PLATE BOUNDARIES
    4. 4. <ul><li>Patterns: </li></ul><ul><li>Not random </li></ul><ul><li>Linear </li></ul><ul><li>Around large inactive plates </li></ul><ul><li>Near areas where elevation is changing </li></ul>
    5. 5. Ring of Fire There are currently about 1500 active volcanoes around the world
    6. 6. Volcanoes <ul><li>Not currently erupting (but still could anytime) </li></ul><ul><ul><li>Dormant (still has seismic activity and lava flow) </li></ul></ul><ul><li>Currently erupting </li></ul><ul><ul><li>Active </li></ul></ul><ul><li>Not able to erupt (permanently) </li></ul><ul><ul><li>Extinct (no seismic activity, no magma flow) </li></ul></ul><ul><li>Magma </li></ul><ul><ul><li>Molten rock material under the surface of the earth </li></ul></ul><ul><li>Lava </li></ul><ul><ul><li>Molten rock material above the surface of the earth </li></ul></ul>
    7. 7. Volcanoes <ul><li>The largest most recent eruption in the US was Mt. St. Helens in Washington State in 1980 </li></ul><ul><li>The largest most recent eruption outside of the US was Mt. Pinatubo in the Philippine Is. In 1991 </li></ul><ul><li>Mt. Kilauea in Hawaii is the world’s most active volcano </li></ul>
    8. 8. Volcanoes <ul><li>The largest volcanic eruption of the twentieth century occurred on the Alaskan Peninsula ( Novarupta – 1912) </li></ul>
    9. 9. Volcanoes <ul><li>How do volcanoes form? </li></ul><ul><ul><li>Deep inside the earth, heat and pressure cause rock to melt and form magma </li></ul></ul><ul><li>Why is magma forced upward toward the earth’s surface? </li></ul><ul><ul><li>Magma is less dense than the rock around it, so it is forced upward towards the earth’s surface </li></ul></ul>
    10. 10. Volcanoes <ul><li>The opening at the top of a volcano is a </li></ul><ul><ul><li>Vent </li></ul></ul><ul><li>The steep walled depression around the vent is the </li></ul><ul><ul><li>Crater </li></ul></ul>
    11. 11. Volcano Structure
    12. 12. Volcanoes <ul><li>Where do volcanoes occur? </li></ul><ul><ul><li>Along plate boundaries and above hot spots AND rift boundaries </li></ul></ul><ul><li>A hot part in the middle of the mantle that melts rock that is then forced upward as magma </li></ul><ul><ul><li>Hotspot </li></ul></ul>
    13. 13. Volcanoes <ul><li>An example of a volcanic area at divergent plate boundaries </li></ul><ul><ul><li>Mid Atlantic Ridge </li></ul></ul><ul><li>An example of a volcano at convergent plate boundaries </li></ul><ul><ul><li>Soufriere Hills Volcano </li></ul></ul><ul><ul><ul><li>(Montserrat, West Indies – 1995) </li></ul></ul></ul>
    14. 14. Volcanoes <ul><li>Volcanic eruptions can be </li></ul><ul><ul><li>Explosive </li></ul></ul><ul><ul><li>Violent </li></ul></ul><ul><ul><li>Quiet </li></ul></ul><ul><li>What 3 factors control the style of a volcanic eruption </li></ul><ul><ul><li>Water Vapor </li></ul></ul><ul><ul><li>Amount of trapped gases </li></ul></ul><ul><ul><li>Magma composition </li></ul></ul>
    15. 15. Volcanoes <ul><li>A volcanoes form depends on whether it is the result of a QUIET or and EXPLOSIVE eruption and whether it is made a silica-rich or silica-poor lava. </li></ul>
    16. 16. Magma! What is the difference between “lava” and “magma”? Magma is below ground and lava is above ground.
    17. 17. Measuring Volcanoes
    18. 18. Novarupta
    19. 19. Volcanoes <ul><li>Shield Volcano: A broad volcano with gently sloping sides, quiet eruptions, silica-poor lava. (ex. Hawaiian Islands) </li></ul>
    20. 21. Volcanoes <ul><li>Cinder Cone Volcano: steep sided volcano, explosive eruptions that throw lava and rock in the air, silica-rich lava (ex. Paricutin in Mexico) </li></ul>
    21. 23. Volcanoes <ul><li>Composite Volcano: a small volcano, both quiet and violent eruptions </li></ul><ul><li>(ex. Mt. St. Helens) </li></ul><ul><li>Also called “stratocones” </li></ul>
    22. 25. Volcanic (lava) Domes <ul><li>A volcanic dome is created when a body of viscous lava slowly pushes its way upward. </li></ul><ul><li>An example is the Dome formed in crater left by 1980 eruption (explosion) of Mount St. Helens. </li></ul>
    23. 26. Volcanic (Lava) Dome Shape
    24. 27. Lava Dome
    25. 28. Volcanoes <ul><li>Tephra: pieces of rock and solidified lava that fall from the air. </li></ul>
    26. 29. Igneous Rocks <ul><li>Volcanic eruptions are the results of the activity of igneous rocks. </li></ul><ul><ul><li>Intrusive Rock formed when magma cools UNDER the ground </li></ul></ul><ul><ul><li>Extrusive Rock form when magma cools ABOVE the ground </li></ul></ul>
    27. 30. Igneous Rock Features <ul><li>Batholiths – largest igneous rocks formed when magma cools underground . </li></ul><ul><li>Dike – magma that is squeezed into a generally VERTICAL crack that cuts across rock layers and hardens </li></ul><ul><li>Sill – magma that is squeezed into a HORIZONTAL crack between rock layers and hardens </li></ul>
    28. 31. Volcanoes <ul><li>Volcanic Neck- the solid igneous core of a volcano left behind when a volcano stops erupting </li></ul><ul><li>Caldera – large opening formed when a volcano collapses </li></ul>
    29. 32. Caldera formation
    30. 34. Volcanoes <ul><li>Igneous Rock – formed when magma hardens below the ground. Eventually, the process of erosion wears down rock at the surface, exposing features such as </li></ul><ul><ul><li>Batholiths </li></ul></ul><ul><ul><li>Dikes </li></ul></ul><ul><ul><li>Sills </li></ul></ul>
    31. 35. Hot Spots <ul><li>Areas of volcanic activity in middle of a plate </li></ul><ul><li>Exact cause is unclear, possibly due to hot area of magma under the lithosphere </li></ul><ul><li>There are two equally valid hypotheses that might explain hot spots: </li></ul><ul><ul><li>The plate could be moving over a stationary hot plume in the mantle, or the hot area causing the volcanic activity may be moving under a static, unmoving surface. At this point in our explorations, we are unable to confirm one or the other hypothesis--each is worthy of consideration. </li></ul></ul>
    32. 36. Examples of Hot Spots
    33. 37. Hot Spot Forming Islands
    34. 38. Hawa’ii
    35. 39. Cascade Range Volcanoes
    36. 40. Cascade Eruptions – 2000 B.C. to Present
    37. 41. Volcanic Results
    38. 44. Volcanic Mud Flow (Lahar)
    39. 45. Pyroclastic Flows This eruption of Mt. Pinatubo caused LOWER GLOBAL TEMPERATURES