Bell Work 10/08/13

1. Bell Work 10/08/13 What features do scientists use to mark the boundaries (edges) of the lithospheric plates (plate boundaries)? Mid Ocean Ridges and deep sea trenches.

2. Types of Plate Boundaries

3. Theory of Plate Tectonics • Explains the following: • How oceans formed • How continents formed • How mountains formed • Cause of earthquakes • Cause of volcanoes

4. Plate Boundaries • Plate tectonics states that the Earth’s crust is broken up into tectonic plates. • These tectonic plates move over the Earth’s surface. • Where two tectonic plates meet is called a PLATE BOUNDARY. • Tectonic plates can be destroyed or created at these plate boundaries.

5. Plate Boundaries • Plate boundaries mark the edge of a tectonic plate. Where two plates meet. • There are three general types: • Convergent (plates move towards each other) • Divergent(plates move away from each other) • Transform(plate move past each other).

6. Divergent Plate Boundary • There are two types: • Mid Ocean ridge – involves creation of new seafloor (oceanic crust). • Rift Valley – involves breaking up a continent (continental crust). • What’s Happening?: A Divergent plate boundary is where two plates are moving away from each other creating new seafloor.

7. Divergent Plate Boundary - MOR Rift Valley Shallow EQ Volcanoes

8. Where do DPB Occur? • MOR: Mid-ocean ridges occur in the center of ocean basins • Rift Valley: Rift valleys occur within a plate involving continental crust.

9. Mid-Ocean Ridge Landforms • Shallow EQ • Non-explosive volcanoes with basaltic magma. • Pillow basalts on seafloor • Hydrothermal vents

10. Rift Valley Landforms • Shallow EQ • Both explosive & non-explosive volcanoes. • Weird magmas • Thinning crust • Long linear valleys • Faulting in crust

11. Mid-Ocean Ridge of Iceland

12. Rift Valley of Africa

13. Red Sea Rift Zone

14. Transform Plate Boundary Characteristics What’s happening? Two plates are sliding past each other. Crust is neither created nor destroyed. • There are two kinds of transform plate boundaries: • Transform fault – associated with continental plate • Fracture zone – associated with mid-ocean ridges • Landforms found on this type of boundary is: • Linear mountains (moderate height) • NO volcanoes • Off set landforms • Moderate earthquakes with a moderate depth

15. Transform Plate Boundary

16. SAN ANDREAS FAULT

17. Fracture Zone Caused by the spherical shape of the Earth

19. Convergent Plate Boundaries (CPB) • Ocean crust is destroyed at convergent plate boundaries or landmasses collide. • Each depends on the type of crust involved: • There are three types of Convergent Plate Boundaries • Ocean vs. Ocean crust (subduction zone) • Continental vs. Ocean crust (subduction zone) • Continent vs. Continent crust (collision zone)

20. Subduction Zone • Defined as a convergent plate boundary where one tectonic plate is destroyed underneath another tectonic plate. • Ocean crust is destroyed at a subduction zone. • Trenches mark the spot where subduction occurs.

21. Ocean-Ocean CPB Characteristics • Plate made of ocean crust is beingdestroyed by subducting under another plate of ocean crust. • Also called a subduction zone. • The older, colder crust will be subducted because it is more dense. • Large (9.0+) powerful earthquakes with tsunamis are common. • Earthquakes are deep (near asthenosphere)

22. Ocean-Ocean Subduction Zone Deep EQ

23. O – O Subduction Landforms • Deep trenches that parallel volcanic islands. • Explosive volcanoes with andesitic magma. • Associated with the ring of fire in the Pacific. • Volcanic island chains (island arcs) form due to ocean to ocean subduction. • Examples: Japan, Indonesia, Philippines, and Aleutian Islands in Alaska

24. Oceanic – Oceanic Subduction Zone

25. Oceanic – Oceanic Subduction Zone

26. Oceanic – Oceanic Subduction Zone

27. Continent-Ocean CPB Characteristics • Plate made of ocean crust is beingdestroyed by subducting under a continental landmass. • Also called a subduction zone. • Ocean crust is subducted because it is more dense. • Large (9.0+) powerful earthquakes with tsunamis are common. • Earthquakes are deep (near asthenosphere)

28. Continent-Oceanic Subduction Zone Volcanic Mountain Chain Trench Deep EQ

29. O-C Subduction Plate Landforms • Subduction zones are marked by trenches. • Deep, powerful EQ occur at all types • Explosive land volcanoes with andesitic magma. • Continental volcanic mountain ranges occur with Ocean to Continent subduction. • Examples: Andes, Cascades in N. America, Mexico & Central America

30. Continental – Oceanic Subduction Zone

33. Continent-Continent CPB Characteristics • AKA “Collision Zone” • Crust is shortened and folded but NOT subducted. • Thick continental crust will not subduct. • Large, inter-continent (9.0+) powerful earthquakes • Earthquakes are deep (near asthenosphere)

34. Continent - Continent Collision Zone No Volcanoes Folded Mountain Range Shallow EQ Deep EQ

35. C – C Collision Landforms • Large folded mountain ranges mark where collision occurred. • NO Volcanoes because there is no subduction. • Crust is shortened and thickened. • Examples: Himalayan Mountains, Alps

36. Formation of Himalayas