The Theory of Plate Tectonics lesson.pptx

volcanoes and plate tectonics

1. The Theory of Plate Tectonics

2. Plate Tectonics

3. What is Plate Tectonics? The EARTH crust and upper mantle are broken into sections called plates Plates move around on top of the mantle like rafts

4. What is Lithosphere? The crust and part of the upper mantle is called Lithosphere. It is 100km thick Less dense that the material below. “It floats”

5. What is Asthenosphere? The plastic layer below the Lithosphere is called asthenosphere. This is where the lithosphere “floats”.

6. There are 2 types of Plates Ocean Plates- Plates below the oceans Continental Plates- Plates below the continents

7. Plate Boundaries

8. Convergent Boundaries It is the boundaries between two plates that are colliding. There are three types of convergent boundaries

9. TYPE 1 Ocean Plate colliding with a dense Continental plate. Subduction Zone : Where the less dense plate slides under the more dense plate Volcanoes: occur at subduction zone.

10. Continental and Oceanic Plates

11. TYPE 2 Ocean Plate colliding with another Ocean plate . The less dense plate slides over the more dense plate creating a subduction zone called TRENCH.

12. TYPE 3 A continental plate colliding with another continental plate. Collisions Zones The place where folded and thrust faulted mountains form.

13. Divergent Boundaries

14. Divergent Boundaries Boundary between two plates that are moving apart or rifting Rifting causes the Seafloor spreading!

15. Features of Divergent Boundaries Mid- Ocean Ridges Rift Valleys Fissure Volcanoes

16. Mid-Ocean Ridges

17. Rift Valleys

18. Fissure Volcanoes

19. Transform Fault Boundaries

20. Transform Fault Boundaries Boundary between two plates that are sliding past each other. Earthquakes along the faults

21. San Andreas Fault

22. Causes of Plate Tectonics

23. Convection Currents Hot Magma in the Earth moves toward the surface, cools, then sinks again. Creates convection currents beneath the plates that cause the plates to move

24. Internal Structure of the Earth

25. Internal Structure of the Earth The Earth has four internal layers: Crust Mantle Outer core Inner core

26. How do we know there are four layers? We don’t, it’s a theory! Using earthquake waves, they can tell whether an object is a liquid or a solid, so by using that information, they theorized about the interior layers of the Earth

27. P waves , meaning primary waves, travel fastest and thus arrive first at seismic stations. The S, or secondary, waves arrive after the P waves.

28. Layers of the Earth Crust Ocean crust: Dark, dense, and thin CRUST: Made out of ocean crust or continental crust Thinnest layer The one we live on We have never dug through this layer Ocean crust: Dark, dense, and thin Continental crust: Light, less dense, and thicker

29. Mohorovičić Discontinuity - The Moho The Mohorovicic Discontinuity, or "Moho," is the boundary between the crust and the mantle. The red line in the diagram shows its location. In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. One of these surfaces exists at an average depth of 8 kilometers beneath the ocean basin and at an average depth of about 32 kilometers beneath the continents. At this discontinuity, seismic waves accelerate. It would be made of elements such as oxygen, iron, sodium, silicon, and aluminum, among others. These elements would be present in rocks that make up both the Earth's crust and mantle.

30. Ocean Vs. Continental Crust Basalt = Ocean Crust Granite = Continental Crust

31. Mantle The mantle is the thickest layer The material is similar to Sapin - sapin —not quite a solid, but not a liquid either The elasticity of the substance allows the plates to move around the planet The mantle is broken into two parts Lithosphere: upper mantle and crust Asthenosphere: lower mantle

32. Outer Core/Inner Core The outer core is made out of liquid Iron and Nickel The inner core is a solid layer made out of Iron and Nickel Both layers make up the majority of the weight of the planet

33. Theory of Continental Drift The theory that continents drifted across the ocean to get their current spots on the globe. First suggested by Alfred Wegner First used the idea of one super giant continent called Pangaea.

34. What was the evidence behind Wegner’s idea? The continents fit together like puzzle pieces. The fossils and rocks on separate continents being identical. Climate regions (found by looking at fossils) that did not match up with the positions the continents are located today.

35. What made it go? Wegner believed that the continents floated on the waters of the ocean to get to their current locations.

36. Convection Current Theory Arthur Holmes elaborated one of the Wegner’s hypotheses that the mantle undergoes thermal convection. This idea is based on the fact that as a substance is heated its density decreases and rises to the surface until it is cooled and sinks again. This repeated heating and cooling results in a current which may be enough to cause continents to move. Initially not accepted, but Harry Hess (1962) published on the Mantle convection current or “sea floor spreading”. This idea was basically the same as that proposed by Holmes over 30 years earlier.

37. SHORT QUIZ

38. What is lithosphere? What is Asthenosphere? Explain the connection between the two? What are the two types of plates? Short Quiz

39. Answer the following question. What type of plate is Plate A? What type of plate is Plate B? Describe what happens to Plate A as it collides with Plate B? As the plate continue to grind against each other, what other geologic event could take place? What geologic feature might form at the surface of plate A? A B