Plate Tectonics Lecture Chapter 2


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Plate Tectonics Lecture Chapter 2

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