Download
volcanoes n.
Skip this Video
Loading SlideShow in 5 Seconds..
VOLCANOES! PowerPoint Presentation

VOLCANOES!

537 Vues Download Presentation
Télécharger la présentation

VOLCANOES!

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. VOLCANOES!

  2. Factors Affecting Eruptions • Magma temperature • Hotter flows easier… • Magma viscosity – determined by temp and composition. High silica = high viscosity (thickness) High viscosity = violent eruptions… • Dissolved gases • More gasses means more violent eruptions…

  3. Volcanic Materials- Lava 3 TYPES OF LAVA FLOWS • Aa- rough and jagged 2) Pahoehoe - wrinkly and ropey texture 3) Pillow - forms underwater at boundaries

  4. Aa Pahoehoe Pillow

  5. Volcanic Materials- Gases • Water Vapor, Carbon Dioxide, Nitrogen, Sulfur Dioxide, and Chlorine Kilauea Volcano, Hawai`i From 1986-2000 emitted 1,000-2,000 metric tons of SO2 every day!

  6. Volcanic Materials • Pyroclastic Materials = Ejected fragments Ash – fine material Cinders and lapilli = medium/pebble sized Bombs and blocks (big stuff) block = hard, bombs = lava

  7. Ash Bombs & Blocks Cinders

  8. Volcanic Terms • Crater – steep walled depression at top • Caldera – large depression in a volcano due to collapse of volcano

  9. Volcanic Terms Conduit – pipe connecting magma chamber to the surface Vent – top of the conduit

  10. Volcanic Terms • Lava plateau – raised flat area of lava • Volcanic neck – remnant of eroded volcano

  11. Columbia Lava Plateau- covers parts of Washington, Oregon, and Idaho

  12. Types of Volcanoes Cinder Cone Composite Shield

  13. Shield Volcanoes • broad base with gently sloping sides Huge in size, mild eruptions, mostly flows, ex: Hawaii Mauna Kea, Hawaii

  14. Cinder Cone • Narrow base and steep sides -Small, violent for size, pyroclastic eruptions, ex: Mt. Paricutin, Sunset crater in AZ

  15. Composite Cone • Medium base and moderately sloped size (volcano looking) Medium size, violent eruptions, andesitic lava, combination of flows and pyroclastic eruptions, ex: Mt. St. Helens

  16. Mt. St. Helens Before & After

  17. Igneous Activity • Plutons (intrusive igneous bodies) • Classified by shape, size, and relationship to surrounding rock layers • Sill – horizontal and between rock layers • Dike – vertical and cut across rock layers • Laccolith – dome/mushroom shaped plutons • Batholith – more than 100 km2 of exposed rock • Stock – less than 100 km2 of exposed rock

  18. Volcano Dangers • Pyroclastic flows – hot gases, glowing ash, and larger rock fragments • Very hot (like cook your butt hot) • Can attain 200 km/hr • Lahars – mudflow formed from volcanic ash and water (melted snow or rain) • Eruptions – you’re there one minute and gone the next…can you say vaporized

  19. Origin of Magma • Read pages 291 – 292 • The role of heat • The role of pressure • The role of water

  20. Volcano Locations • Convergent plates • Subducting plate melts and magma rises • Japan and Mt St Helens • Divergent plates • Plate diverge and magma rises through the rift • Mid-ocean ridge • Iceland • East African Rift • Intraplate (hot spots) • Mantle plume rises towards the surface • Hawaii and Yellowstone