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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
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. Plate Tectonics and Igneous Rocks
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

13. Composite Cones - Stratovolcano
Most encircle the pacific ocean (ring of fire) as part of magmatic arcs
Large – ~1 km high, 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
Plate Tectonics and Igneous Rocks

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