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Question of the Day

Question of the Day. Question: How do we find the epicenter of an earthquake? Answer: … … …. Turn In: A Whole Lot of Shakin ’ Finding an Earthquake ’ s Epicenter. Lava & Volcanoes. Types of Lava Composition. Quartz. Felsic lava/magma -sic = silica = quartz = SiO 2

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Question of the Day

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  1. Question of the Day Question: How do we find the epicenter of an earthquake? Answer: … … … • Turn In: • A Whole Lot of Shakin’ • Finding an Earthquake’s Epicenter

  2. Lava & Volcanoes

  3. Types of Lava Composition Quartz • Felsic lava/magma • -sic = silica = quartz = SiO2 • Forms continental crust • Lighter colored rocks • lower density rocks Granite Feldspar

  4. Types of Lava Composition • Mafic lava/magma • -fic = ferric = Fe = iron • Forms oceanic crust • Darker colored rocks • higher density rocks Hornblende Basalt

  5. Mafic Lava • Mafic Lava • Magma from the mantle rises to the surface • Magma melts through oceanic crust only • Very little SiO2 is picked up by the magma • Erupting lava is mafic in composition

  6. Mafic Lava • At which plate boundaries does mafic lava erupt? • Continental/Oceanic Convergent • Oceanic/ Oceanic Convergent • Continental/ Continental Convergent • Divergent

  7. Mafic Lava • At which plate boundaries does mafic lava form? B. Oceanic/ Oceanic Convergent D. Divergent

  8. Felsic Lava • Felsic Lava • Magma from the mantle rises toward the surface • Magma melts through continental crust • Lots of SiO2 is picked up by the magma from the continental crust • Erupting lava is felsic in composition

  9. Felsic Lava • At which plate boundaries does felsic lava form? • Continental/Oceanic Convergent • Oceanic/ Oceanic Convergent • Continental/ Continental Convergent • Transform

  10. Felsic Lava • At which plate boundaries does felsic lava form? • Continental/Oceanic Convergent

  11. Why is SiO2 important? • SiO2 thickens lava • Changes appearance of igneous rocks produced • Changes types of volcanoes produced • Changes the style of eruptions from those volcanoes

  12. SiO2 & Rocks • SiO2 makes igneous rocks lighter in color • Which of these rocks is felsic? B. Basalt A. Granite

  13. SiO2 & Rocks • SiO2 makes igneous rocks lighter in color • Which of these rocks is felsic? B. Basalt- MAFIC A. Granite- FELSIC

  14. SiO2 & Rocks • Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks • Denser • Less dense • Heavier • Darker

  15. SiO2 & Rocks • Since felsic lava is formed from continental crust, felsic rocks will be _______________ than mafic rocks • Denser • Less dense • Heavier • Darker

  16. Properties of Felsic Lava • Very thick, slow-moving (high viscosity) • Lava cools before it moves very far • Volcanoes are • Narrow with steep sides • Wide with shallow sloping sides

  17. Properties of Felsic Lava • Very thick, slow-moving (high viscosity) • Lava cools before it moves very far • Volcanoes are • Narrow with steep sides • Wide with shallow sloping sides

  18. Properties of Felsic Lava • High viscosity makes it difficult for volcanic gases (CO2,SO2,H2O) to escape • Trapped gases cause eruptions to be more explosive Mt. Pinatubo 1991

  19. Composite Cone/Stratovolcano • Up to 22,000 feet tall • steep-sided, symmetrical cones • Eruptions are extremely explosive Mount Fuji, Japan

  20. Composite Cone/Stratovolcano • alternating layers of lava flows, volcanic ash, and rocks. • Created from felsic lava

  21. Volcanic Dome/ Lava Dome • Rebuilding Stratovolcano • Steep sides because lava cools quickly, before spreading out • Created by felsic lava • Eruptions are extremely explosive Mt. St. Helens, WA (before and after)

  22. Properties of Mafic Lava • Thin, fast- moving lava/magma (low viscosity) • Lava spreads out and cools • Produces wide volcanoes • Volcanic gases escape easily • Eruptions are _______________ A. Explosive B. Not very explosive

  23. Properties of Mafic Lava • Thin, fast- moving lava/magma (low viscosity) • Lava spreads out and cools • Produces wide volcanoes • Volcanic gases escape easily • Eruptions are _______________ B. Not very explosive

  24. Shield Volcano • broad, gentle slopes • Created by fluid mafic lava that spreads out quickly before cooling • largest volcanoes on Earth Kilauea, Hawaii Mauna Loa, Hawaii

  25. What about hot spots? • Hawaii • Magma melts through oceanic crust so lava is • Mafic B. Felsic

  26. What about hot spots? • Hawaii • Magma melts through oceanic crust so lava is • Mafic

  27. What about hot spots? • Hawaii • Magma melts through oceanic crust so lava is • Mafic • Yellowstone • Magma melts through continental crust so lava is A. Mafic B. Felsic

  28. What about hot spots? • Hawaii • Magma melts through oceanic crust so lava is • Mafic • Yellowstone • Magma melts through continental crust so lava is B. Felsic • It all depends on the type of crust it’s under!

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