1. Plate Tectonics - The Engine That Drives the Rock Cycle Jim Miller Dept of Geological Sciences Precambrian Research Center University of Minnesota- Duluth

2. Geological Processes Melting 2 Compaction & Cementation Cooling & Crystallization Tectonic Uplift Erosion, Transportation & Deposition Weathering Melting 1 Subduction Heat & Pressure Precipitation Earth Materials SEDIMENTARY ROCKS MAGMA VOLCANIC ROCKS SEDIMENT INTRUSIVE ROCKS METAMOPHIC ROCKS SOIL

3. Rock Cycle Basalt Granite Mafic Quartz + Clay+Lithics Felsic Gabbro Rhyolite Clay+Lithics Graywacke Shale Slate Schist Gneiss Migmatite Qtz Sandstone Limestone Quartzite Marble Greenstone Amphibolite

4. Overview of Plate Tectonics Jim Miller

5. Plate Tectonic Theory The Earth’s outer shell (lithosphere) is composed of rigid plates that are moving relative to one another.

6. Physical and Chemical Structure of the Earth Chemical Layers Physical Layers Lithosphere Compositional Components of the Lithosphere Continental Crust – ~62% SiO 2, low density rocks, “felsic” Oceanic Crust - ~ 48% SiO 2, high density rocks, “mafic” Lithospheric Mantle - ~ 40% SiO 2, very high density rocks, “ultramafic” Lithospheric Mantle

7. Plate Tectonics drives 2 Stages of Crust-making 1. Mantle partially melts to make ocean crust 2. Ocean crust melts to make continental crust

8. What moves the Plates? Slab Pull - densification of subducted plate pulls the plate into the mantle Mantle Push - Upwelling of the asthenospheric mantle pushes the plates apart Ridge Slide – Thermal upwelling at ridges causes plates to separate by sliding downhill (by gravity) Problem - we are not sure how the mantle is structured.

9. Types of Plate Boundaries

10. Divergent Plate Boundaries Mid-ocean Ridges Where Stage 1 Crust is Made

11. Youthful Oceanic Crust 200 100 0 Ma

12. Basalt – Rock Type of the Oceanic Crust Remember: Melting the Mantle Makes Mafic Magma!! Always

13. Continental Rifting The creation of new ocean basins

14. Continental Rifting and The Break-up of Pangea

15. Convergent Boundaries Making 2 nd Stage Crust Ancient Continental Crust

16. Convergent Boundaries- Where the Action Is!! Ocean- Continent Continent - Continent Ocean - Ocean Earthquakes Volcanoes

17. Mt. St. Helens May 18, 1980 Consequences of Convergence Explosive Volcanism

18. Consequences of Convergence Mountain Building and Rock Deformation

19. Consequences of Convergence - Earthquakes 1326 Aftershocks

20. OROGENESIS The Culmination of Convergence

21. San Francisco Earthquake April 18, 1906 Mag 7.8 Transform Boundaries Connects other Boundaries

22. Mantle Plumes (Hotspots) Creation of overthickened oceanic crust

23. Famous Hotspots Hawaii Yellowstone Iceland

24. Plate Tectonics - The Engine That Drives the Rock Cycle Use Illustrations as Rock Cycle Story Starters