• Like
Plate tectonics
Upcoming SlideShare
Loading in...5
×

Plate tectonics

  • 2,761 views
Uploaded on

 

More in: Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
2,761
On Slideshare
0
From Embeds
0
Number of Embeds
2

Actions

Shares
Downloads
196
Comments
0
Likes
2

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Plate Tectonics Continental Drift
  • 2. 4-1 Continental Drift – objectives…
    • Explain Wegener’s hypothesis of continental drift.
    • List evidence for Wegener’s hypothesis of continental drift.
    • Describe seafloor spreading.
  • 3. Continental Drift
    • Began with observations made over 400 years ago.
    • The first reliable maps were studied and it was noticed that the continents fit together like a puzzle.
  • 4. Hypothesis on Continental Drift.
    • The continents were once part of the same landmass – Pangea
    • Surrounding Pangea was a great ocean – Panthalassa
    • About 200 mya, Pangea began breaking apart.
    • This motion caused crumpling which led to today’s land features.
  • 5. Alfred Wegener
    • A german scientist.
    • Proposed his hypothesis on continental drift in 1912.
  • 6. Observations led to questions…
    • Were the continents once part of the same landmass?
    • If so, what caused this landmass to break apart?
    • What caused the continents to move to their present locations?
  • 7.  
  • 8.  
  • 9. Evidence
    • Coastline similarities
  • 10. Evidence
    • Fossils
      • Mesosaurus
      • Cynognatyhus
      • Lystrosaurus
      • Glossopteris
  • 11.  
  • 12. Geologic Evidence
    • Age and types of rocks
    • Mountains
      • Applachian mountains fit continuously with a band of mountains in Greenland.
  • 13. Climatic Evidence
    • Layers of glaciers in southern Africa and South America
    • Coal deposits in the Eastern US, Europe, and Sibera
    • These climatic similarities are easy to explain if the continents were once joined.
  • 14. Climatic Evidence - glaciation
    • Evidence of ancient glaciation indicated that parts of southern Africa, India, Australia, and South America were covered by a large ice sheet. Arrows indicate direction of ice movement.
  • 15. There was little support for Wegner’s hypothesis….until.two decades after his death…
  • 16. Seafloor Spreading
    • 1947, mapping the Mid-Atlantic Ridge
      • Discovered the ocean floor is much younger than continental rocks.
        • Oceanic rocks – 150 million years old
        • Continental rocks – 4 billion years old
    • Harry Hess suggested a hypothesis
      • Seafloor spreading
        • Rocks in/near the rift were younger as a result of the upwelling and solidification of magma.
  • 17. Seafloor Spreading
    • Seafloor spreading provided the support Wegner needed for a mechanism for continental drift.
    • Still no proof…
  • 18. Paleomagnetism
    • Magnetism resulting from the cooling of magma mirrors the existing magnetism of the earth.
    • Magnetic orientations were discovered that appeared normal then reversed…normal then reversed…
    • This supported seafloor spreading…and thus further anchored Wegner’s Hypothesis.
  • 19. Paleomagnetism
  • 20. Review of 4-1…
    • What observation first led to Wegner’s hypothesis of continental drift?
    • What types of evidence support Wegener’s hypothesis?
    • Describe the process of seafloor spreading.
    • Explain how scientists know that the earth’s magnetic poles have reversed themselves many times during earth’s history.
  • 21. 4-2 – Plate Tectonics - objectives
    • Summarize the theory of Plate Tectonics.
    • Compare the characteristic geologic activities that occur along the three types of plate boundaries.
    • Explain the possible role convection currents in plate movement.
    • Summarize the theory of suspect terranes.
  • 22. A theory emerges…
    • 1960’s…
    • A combination of continental drift and seafloor spreading…
    • Describes continental movement but also proposes a possible explanation of why and how continents move.
  • 23. The Earth’s Layers
    • Two types of crust:
      • Oceanic – ocean floor
      • Continental – dry land
    • Both types of crust plus the rigid upper mantle make up the Lithosphere.
    Himilayian Crust
  • 24. The Earth’s Layers
    • Lithosphere – the thin outer layer
      • Lithospheric plates
    • Asthenosphere – a layer of “plastic” rock
      • Denser than the lithosphere.
  • 25. Earth’s Layers
  • 26. Lithospheric Plate Boundaries
  • 27. Lithospheric Plate Boundaries
    • Continent margins don’t necessarily follow plate boundaries.
    • 30 plates have been identified at some speed of constant motion.
  • 28. Types of Plate Boundaries
  • 29. Divergent Boundaries
    • spreading centers where two lithospheric plates move away from each other
  • 30. Divergent Boundaries
  • 31. Convergent Boundaries
    • A converging boundary forms when two plates move toward each other
    • Two Types
      • Collision
      • Subduction
  • 32. Convergent Boundary - Collision
    • Oceanic crust – Oceanic crust
  • 33. Convergent Boundary - Collision
    • Oceanic crust – continental crust
  • 34. Convergent Boundaries
    • Continental crust – continental crust
  • 35.  
  • 36.  
  • 37. Transform Fault Boundaries
    • San Andreas fault, California
  • 38. Causes of Plate Motion
    • Many scientists think that the movement of the lithospheric plates is due to convection currents.
  • 39. Convection Currents