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Unformatted text preview: Building a Volcano Melting at the Mantle Pre-Er uption I nf lation Change in tilt, distance Number of Ear thquakes olcano inf lates pr ior to er uption Volcano in repose Int roduction to Volcanoes What is a volcano?- A place on the earths surface where molten rock and gases are erupted.- A hill or mountain built up by the eruption of molten rock Stratavolcano Ideal Volcano- Cones are built up of layers of lava and volcanic ash.- Examples: o Mount Hood, Cascades o Mount Shasta, Cascades Cinder Cones - Simplest type of volcano - Built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone.- Examples: o Haleakala, H I o Surtsey, Iceland o Paricutin, Mexico Shield Volcanoes- Formed mostly from the solidification of lava flows of basalt- Lava flows are low viscosity fluid travels great distances- Examples: o Mauna Loa, H I Worlds largest volcano 13,690 ft about sea level 33,000 ft from ocean floor o Mauna Kea, HI o Kilauea, HI o Newberry, Oregon- Composed of vicious lavas and ash, shield volcanoes are made of fluid basalt lava flows- Lava flows give volcanoes a shield like shape 1- Olympus Mons o Giant shield volcano on Mars o Believed to be the largest volcano in the solar system Holes and Craters- Mars and explosion craters are produced when hot magma reacts violently with shallow water or water soaked ground- Example: o Zuni Maar, New Mexico o Vitti, Iceland o Crater Lake, Oregon Different kind of hole in the ground What is now left of a large stratavolcano that blew itself to bits 6,845 years ago o Long Valley Caldera, CA Some volcanic holes in the ground are too big to be appreciated Formed by a collapse bout 760,000 years ago following a gigantic explosion Last eruption was 600 yrs ago Fissures- Lava erupting from cracks can produce huge thick piles of lava o Eastern Iceland o Krafla, Iceland o Snake River Plain, Idaho Where do volcanoes occur?- Plate Margins o Spreading Margins Mid-Ocean Ridges Iceland Rifting Continents E. African Rift o Converging Margins Island Arcs Aleutians, Japan Continental Margins Cascades, Andes- Plate Interiors o Oceanic Plates - Hawaii o Continental Plates Yellowstone Volcanic Activity- Total number of recognizable volcanoes: 10,000- Active Volcanoes known to have erupted during historical times - 529- Dormant Volcanoes that have no erupted during historical times, but will probably erupt again 1,340- Extinct Volcanoes that are unlikely to erupt again- 500 currently active volcanoes- 5-10 volcanoes erupt per month (50/yr)- 262,000 people have been killed by volcanoes since 1600 A.D....
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This note was uploaded on 03/17/2009 for the course GEO SCI 105 taught by Professor Rhodes during the Spring '06 term at UMass (Amherst).
- Spring '06