Tectonic boundaries and hot spots

1. Tectonic boundaries and hot spots

2. A useful reference http://www.learner.org/interactives/dynamicearth/sitemap.html http://pubs.usgs.gov/gip/dynamic/dynamic.html#anchor19309449

3. Types of Plate Boundaries • Divergent - Pull apart- Mid Ocean Ridges • Convergent- Come together- subduction zones- Andes Mts. • Transform- sliding past each other- San Andreas fault zone California

4. The all inclusive Plate boundary picture

5. Volcanoes • Mid Ocean volcanoes • Mostly basaltic • Source of magma is hot mantle area. • Shield type volcanoes • Continental Margins and Island Arcs • Source of Magma is mostly remelting of pre-existing rocks, through the continental crust, producing Andesite and Rhyolite lavas • Stratovolcanoes

6. Earthquakes • Earthquake locations are used to determine the plate boundaries. • Plates are the large pieces of the earth that have few earthquakes, the boundaries are where the earthquakes occur because this is where the blocks of the earth are interacting with each other, pushing into each other, sliding past each other

7. Tectonic boundaries and hot spots

8. Mid-ocean Ridges with Transform FaultsThe orientation of Transform faults help to determine plate motion direction. These have shallow earthquakes

9. Trenches at Island ArcsThese have shallow to deep earthquakes and usually rhyolitic flows

10. The west coast shows aspects of both subduction in the north and transform motion in the south

11. The Formation of granitic bodies as a result of subduction and melting of surface rocks

12. Erosion of the Earth’s surface exposes these granitic bodies

13. Major locations of granitic bodies in the North America

14. The Plate Boundaries with the motion of the plates indicated by arrows

15. Convective heat flow from inside the Earth is the ultimate cause of volcanoes, earthquakes, and plate motion. When the Earth cools completely –no more volcanoes etc.

16. Earthquake Waves • There are three types of seismic waves that travel through and on the earth • P waves - Compressional travel about 6 km/sec • Travel trough both solids and liquids • S waves – Shear waves travel about 4 km/sec • Travel only through solids (not the liquid outer core) • Surface waves- travel only along the surface at about 3.5 km/sec

17. Seismic Body Waves

18. Shadow Zones…How do we know how big the liquid core is?

20. Interior of the Earth • The earth’s interior is divided into Crust 0-35 km • Mantle 10-2900 km • Outer Core 2900-5200 km • Inner Core 5200-6000 km • From Earthquake studies • Also: Lithosphere 0-100 km • Asthenosphere 100-700 km • Based on rigid vs. plastic

22. HOT SPOTS OF THE WORLD

23. Hot spots can show the direction of plate motion

24. Problems Not solved • Driving Mechanism • Why Hot Spots • How deep does convection take place

25. Driving forces :Convection, Slab pull, Ridge push

26. Some mineral locations of North America

27. Types of mountains or mountain ranges • Volcanic- West coast –Mt. Rainer • Fault, trusting – Western U.S. Basin and Range area- Nevada • Folded – Appalachian Mts. Eastern Pa, West Virginia etc.

28. USA Relief Map

29. Pennsylvania - folded ridge and valley area

30. Metamorphic region of Eastern U.S,

31. Wisconsin Tectonic History 1

32. Wisconsin Tectonic History 2

33. Wisconsin Tectonic History 3

34. Igneous Adirondacks NY

35. Typical compass for class use

36. Direction a compass points in U.S.

37. Earth’s Dipole Magnetic Field

38. Reversal of the Earth’s magnetic Field Present world - arrows in at North Reversed field – arrows out at North

39. Before 500 years before middle of reversal Middle of reversal 500 year after middle of reversal

40. Example evidence from Igneous rocks: Lava flows and sea floor magnetic anomalies

41. Comparison of Polar wander curves

42. Wisconsin Aeromagnetic map

43. The complex geologic tectonics of the Midwest