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Volcanoes

Volcanoes. Volcano : an opening in the earth’s surface through which lava, hot gases, and rock fragments erupt. How do they form?. Magma 50-100 miles below the earth’s surface slowly begins to rise to the surface As the magma rises it melts gaps in the surrounding rock

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Volcanoes

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  1. Volcanoes

  2. Volcano: an opening in the earth’s surface through which lava, hot gases, and rock fragments erupt

  3. How do they form? • Magma 50-100 miles below the earth’s surface slowly begins to rise to the surface • As the magma rises it melts gaps in the surrounding rock • As more magma rises a large reservoir forms as close as 2 miles below the surface (magma chamber)

  4. How do they form? • 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)

  5. How do they form? • The magma, now called lava, builds up at the vent forming a volcano

  6. How do they Form? • Often the volcano sides will be higher than the vent forming a depression called a crater

  7. Crater:

  8. Caldera: an unusually large crater or the remains when the cone collapses into its own magma chamber

  9. The Birth of a Volcano

  10. Anatomy of a Volcano Cone: the above ground structure built from lava and/or tephra

  11. Conduit: the path that magma takes from the magma chamber to the vent

  12. Magma Chamber: the reservoir located under the volcano where magma collects and becomes the supply of magma/lava to build the volcano

  13. Lava: molten, liquid rock on the surface of the earth

  14. Parasitic Cone: • a smaller secondary volcano built on the side of or near the main volcano, but sharing the same conduit to the magma chamber

  15. Fumarole: a secondary vent that emits only gases

  16. Fissure: a long fissure (crack) from which lava flows

  17. Vent: opening of the volcano, through which lava, ash and gases flow

  18. Take a minute to label the parts on the diagram (not all parts are shown)

  19. Crater Ash Cloud/Gases Vent Parasitic Cone Lava Flow conduit mantle Magma chamber

  20. Types of Volcanic Eruptions Two factors determine the type of eruption: • Amount of water vapor & other gases in the magma • The chemical composition of the magma

  21. Explosive Eruptions • Trapped gases under high pressure will violently explode when the magma reaches the lower pressure of the surface.

  22. Explosive Eruptions • Has granitic magma is very thick and plugs the vent causing the pressure to build until it blows violently out the vent Mt. St. Helens

  23. Explosive Eruptions • The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions Mont serrat

  24. Explosive Eruptions-Examples Mt. Fuji Mt. Pinatubo Mt. St. Helens

  25. Eruption of Mt. St. Helens

  26. Quiet Eruptions • Low pressure gas

  27. Quiet Eruptions • Has basaltic magma (is more fluid and will flow instead of explode)

  28. Quiet Eruptions • …and has low water content • Examples: Hawaii

  29. Typical Hawaiian Eruption

  30. Directed Reading!!! Pg. 1–2 Textbook pg. 438

  31. Get outyour Directed Reading!!! Pg. 1-2 Find a Checking Pen & Your Volcano Notes!!

  32. Cinder cones

  33. Cinder Cone Volcanoes

  34. Cinder Cones:

  35. Shield volcanoes

  36. Shield Volcanoes 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. Shield volcano on Mars; Taken from space

  37. Shield Volcanoes Mauna Kea

  38. Composite or strato

  39. Composite or strato

  40. STrato/Composite Llaima Volcano, Chile.

  41. Composite (strato) Volcanoes examples: Mt. Fuji Mt. Rainier Mt. Kilimanjaro

  42. Types of Volcanoes Review

  43. Where do Volcanoes Occur?

  44. Where do Volcanoes Occur?

  45. Where do Volcanoes Occur?

  46. Cascade Volcanoes

  47. Where do Volcanoes Occur?

  48. Hot Spots: Formation of the Hawaiian Islands

  49. What comes out of volcanoes? • Lava • Tephra • Gases

  50. Lava—3 kinds:

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