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Page 160. Daily Question. At which type of plate boundary would you find mafic igneous rocks? Explain Would the rocks be basalt, gabbro, or could both rock types occur? Explain . Fig. 6.6. Plate Tectonics and Igneous Rocks. Ophiolite Complex. Oceanic Crust Marine Sediment

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Page 160

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  1. Page 160

  2. Daily Question • At which type of plate boundary would you find mafic igneous rocks? Explain • Would the rocks be basalt, gabbro, or could both rock types occur? Explain

  3. Fig. 6.6 Plate Tectonics and Igneous Rocks

  4. Ophiolite Complex Oceanic Crust Marine Sediment Pillow Basalts Sheeted Dikes Gabbro

  5. Pillow Basalts in the Ocean

  6. Pillow Basalts on the Continents

  7. Sheeted Dikes

  8. Gabbro

  9. Fig. 6.6 Plate Tectonics and Igneous Rocks

  10. Cinder Cones • Built from ejected lava fragments • Have steep slopes (controlled by angle of repose – the steepest angle at which material remains stable) • Small – 300 m (1000 ft) high, 2 km in diameter

  11. Composite Cones - Stratovolcano • Most encircle the pacific ocean (ring of fire) as part of magmatic arcs • Large – ~1 km high, 5 - 25 km wide • Symmetrical structure • Composed of alternating lava flows and pyroclastic deposits • Product of high viscosity magma • Have violent eruptions Mount Rainer

  12. Fig. 6.6 Plate Tectonics and Igneous Rocks

  13. Hot Spots

  14. Produced by rising plume of mantle material (mantle plume) • They are stationary – plates move over the hotspots

  15. Basalts produced by hot spots are chemically different from basalts produced at MOR

  16. Hot Spot Example – Island Chains

  17. Island Chain Formation

  18. Hot Spot Under Hawaii • Notice linear layout of islands • Could determine plate movement rate for data • Island continually being formed

  19. Shield Volcanoes • Broad, slightly domed strucutre • Large structure 9 km (~6 miles) high & 50 km (~30 miles) wide • Produced by fluid (low viscosity) lava • Example: Mauna Loa, Kilauea, other island chains

  20. Shield Volcanoes

  21. Volcano Size Comparison

  22. Hot Spot Example – Continental • Yellowstone

  23. Continental Hot Spot Mechanics

  24. Volcanism and Continental Hot Spots

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