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. Plate Tectonics and Igneous Rocks Fig. 6.6

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. Plate Tectonics and Igneous Rocks Fig. 6.6

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

13. 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

14. Plate Tectonics and Igneous Rocks Fig. 6.6

15. Hot Spots

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

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

18. Hot Spot Example – Island Chains

19. Island Chain Formation

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

21. 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

22. Shield Volcanoes

23. Volcano Size Comparison

24. Hot Spot Example – Continental  Yellowstone

25. Continental Hot Spot Mechanics

26. Volcanism and Continental Hot Spots