Plate Tectonics Lecture Chapter 2
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Plate Tectonics Lecture Chapter 2

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continental drift

continental drift

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  • 1. Plate Tectonics Mr. McKay Earth Science
  • 2. Drifting Continents
    • Evidence of drifting
      • Fossils found on both of the continents of Africa and South America that are of the same organism
        • Fossils: The preserved remains of ancient organisms
      • German scientist Alfred Wegner came up with the theory of continental drift , he was actually a meteorologist and not a geologist
        • The theory called the giant landmass that once was on Earth Pangaea
          • Pangaea : Means all Earth
    • Early Earth & Plate Tectonics
  • 3. Fossil Evidence
    • Fossils play a key role in supporting the theory of Continental drift
      • Glossopteris is an extinct plant
        • They are found in rocks that are around 250,000,000 years old ( 250 million)
        • The seeds were to large to be carried by wind and too fragile to have survived ocean waves
        • The fact that they are found in Antarctica implies that they had to be in a better climate than what is present Antarctica
  • 4. Fossils
    • Glossopteris: a fern found on the southern continents
    • Cynognathus: a land reptile found in South America and Africa
    • Lystrosaurus: a land reptile found in Africa, Antarctica, and India
    • Mesosaurus: a freshwater swimming reptile found in Africa and South America
  • 5. Fossil Evidence
    • From Rocks
      • Not only fossils provide evidence for theory support
        • Rocks in Africa and South America
          • When you examine the continents from these two they look as if they could piece together like a puzzle
          • The layers of coal depth line up with each other
          • Rock deposits from glaciers also match
  • 6. Divergent Boundary
    • Divergent Boundaries
      • Constructive-add new land
      • Mid-ocean Ridge
        • Ocean floor moves away on either side of the ridge
        • Called sea-floor spreading
        • Often offset by transform faults which causes a curve in the ridge
    Transform Faults Sea-Floor Spreading/Mid-Ocean Ridge Spreading Sea Floor Basic Plate Boundaries
  • 7. Magnetic Rock Strips
    • Some minerals have magnetic properties
    • These minerals line up with the Earth’s magnetic poles
    • When the molten rock hardens, a permanent record of the Earth’s magnetism remains
    • The Earth’s magnetic poles have reversed themselves from time to time
    • Animation
    • Sea Floor Spreading
  • 8. Convergent Boundaries
    • Plates collide-destructive
    • Two continents colliding build mountains or plateaus
    • The Indian Plate and the Eurasian Plate collide to form the Himalayas which have Mt. Everest , the highest mountain on Earth.
  • 9. Convergent Boundary
    • Destructive-crust is destroyed (melted by the mantle)
    • Called Subduction
    • When oceanic and continental crust collide
    • Oceanic crust is pushed down into the mantle and melted
    • Some of this melted material surges upward
  • 10.
    • The continental crust is also forced upward producing volcanoes
    • The Cascade Range in Washington and Oregon are an example of this
    Convergent Boundaries Convergent Boundaries
  • 11. Convergent Boundaries
    • When two oceanic plates collide subduction occurs
    • The older denser plate is pushed into the mantle and melted
    • Some of the material rises upward and erupts on the ocean floor forming an island arc
  • 12. Theory of Plate Tectonics
    • Tectonics: refers to the branch of geology that is concerned with plate movements
    • Theory of Plate Tectonics: Links together the ideas of continental drift and ocean floor spreading to explain how the Earth has evolved over time.
      • It explains the formation, movements, collisions, and destruction of the Earth’s crust
      • According to the theory the Earth’s uppermost layer, called the lithosphere, is made up of plates
  • 13. Lithospheric Plates
    • There are seven major plates
      • The Pacific Plate-
        • which covers 1/5 of the Earth
      • North American
      • South American
      • Eurasian
      • African
      • Indo-Australian
      • Antarctic Plates
    • There are also Many smaller plates
      • Caribbean
      • Arabian
    • Plate Tectonics Review