Evidence for continental drift

  • Created by: EEC2145
  • Created on: 11-01-23 12:31
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  • Evidence for continental drift
    • Modern evidence
      • Mantle tomography
        • We have images of the mantle moving based off earthquake waves.
        • Discovered 1960s.
      • Paleomagneti-sm
        • New volcanic rock (basalt) is formed at the ridge, when cooled it magnetises.
        • The crystals rotate and align with the current field allowing the age to be found
          • Discovered by magnetic surveys in the 1960s
          • Lead to Vine and Matthews proposing the theory of sea floor spreading
      • Age of rocks in the Atlantic
        • Maurice Ewing discovered the Mid-Atlantic Ridge in 1948
        • Harry Hess dated the rocks in 1962.
      • Locations of volcanoes and earthquakes
        • They mainly follow Earth's tectonic plate boundaries where the plates meet
      • GPS tracking
        • GPS receiver pins are dropped on the ocean floor and plates can be watcher moving in real time.
          • 1990s-2000s
    • Wegner's evidence 1912
      • Continental fit and matching geology
        • Rocks of similar age, type and formation are found in Southeast Brazil and Southern Africa
        • The continents fit together like a puzzle
          • The best fit is 1000m below sea level with South America and West Africa
        • Coal deposits are found in North America, UK, Northwest Eurpoe and Antarctica.
          • Coal can only form in warm, wet conditions yet not in current locations
        • North America and Europe have mountain ranges that match up when pushed together (Appalachians with belts in Europe and the UK)
        • Geology of Eastern South America and West Africa was mapped to reveal ancient rock outcrops (cratons) over 2000 million years old were continuous from one to the other
      • Animals and Plants
        • Many examples of fossils are found on separate continents and nowhere else
          • Mesosaurus (freshwater crocodile-like creature) (286-258 million years ago)
            • Solely found in Southern Africa and Eastern South America.
            • Would have been physiologically impossible for them to swim the Atlantic
          • Glossopteris (woody, seed-bearing shrub or tree)
            • 299 million years ago
            • Found in Australia, South Africa, South America, India and Antarctica
            • Embedded in the same layer sequence but each continent has a different climate now
        • When the continents of the Southern hemisphere are re-assembled into the single land mass on Gondwanaland
      • Past glaciations.
        • Present day tropical locations show evidence of past glaciations
          • These must have been in a different location previously
            • Glacial deposits formed 300 million years ago are found across the Southern hemisphere
        • Glacial striations (scratches and gouges from glacial abrasion) found in African deserts
        • Glacial deposits formed 300 million years ago are found across the Southern hemisphere


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