Continental Drift and Plate Tectonics

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Questions and Answers

What is the process called through which tectonic plates interact and move?

  • Plate dislocation
  • Continental drift
  • Seafloor expansion
  • Plate tectonics (correct)

Which of the following supercontinents existed over a billion years ago?

  • Rodinia (correct)
  • Pangaea
  • Laurasia
  • Pannotia

At what rate are the North American and Eurasian tectonic plates moving away from each other?

  • 1 centimeter per year
  • 0.5 centimeters per year
  • 5 centimeters per year
  • 2.5 centimeters per year (correct)

What geological feature is formed by the process of seafloor spreading?

<p>Mid-ocean ridges (B)</p> Signup and view all the answers

What was one major flaw in Wegener's theory of continental drift?

<p>It did not explain the mechanism behind continental movement. (C)</p> Signup and view all the answers

What will happen to the African continent along the Great Rift Valley system?

<p>It will split into two separate continents. (D)</p> Signup and view all the answers

What substance aids in the process of seafloor spreading by rising from within the Earth?

<p>Magma (C)</p> Signup and view all the answers

What is a significant characteristic of the tectonic plates?

<p>They float on the Earth's mantle. (C)</p> Signup and view all the answers

Who is most associated with the theory of continental drift?

<p>Alfred Wegener (B)</p> Signup and view all the answers

What was the name of the supercontinent that Wegener proposed existed?

<p>Pangaea (B)</p> Signup and view all the answers

Which fossil evidence did Wegener use to support his theory of continental drift?

<p>Mesosaurus (C)</p> Signup and view all the answers

What type of climate evidence did Wegener find in Svalbard, Norway?

<p>Tropical plant fossils (A)</p> Signup and view all the answers

How did Wegener demonstrate the geological relationship between continents?

<p>By examining rock layers and mountain ranges (B)</p> Signup and view all the answers

What did Wegener believe about the movement of continents?

<p>They move slowly and constantly. (A)</p> Signup and view all the answers

Approximately how many million years ago did Pangaea begin to break up?

<p>200 million years ago (B)</p> Signup and view all the answers

What was Wegener's profession before he proposed the theory of continental drift?

<p>Astronomer (B)</p> Signup and view all the answers

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Study Notes

Continental Drift and Plate Tectonics

  • Continental drift was an early theory explaining how continents moved, largely associated with Alfred Wegener.
  • Wegener proposed that all continents were once part of a singular landmass known as Pangaea.
  • He published his theory in the early 20th century based on evidence from biology, botany, and geology.

Evidence for Pangaea

  • Fossils of the mesosaurus, a freshwater reptile, are found exclusively in southern Africa and South America, indicating a shared habitat.
  • Plant fossils discovered in Svalbard, Norway, are of tropical species, suggesting it had a warm climate in the past.
  • The fit of the east coast of South America with the west coast of Africa resembles a jigsaw puzzle, showing geological similarities.
  • Appalachian Mountains in the eastern USA share geological traits with the Caledonian Mountains in Scotland.

Timeline of Pangaea

  • Pangaea existed approximately 240 million years ago and started breaking apart around 200 million years ago.
  • Several supercontinents have formed and fragmented during Earth's history, including Pannotia (600 million years ago) and Rodinia (over 1 billion years ago).

Tectonic Activity

  • Wegener's theory lacked a mechanism to explain continental movement, leading to skepticism among scientists.
  • Current understanding attributes continental movement to tectonic plates, massive rock slabs that constantly shift and interact.

Seafloor Spreading and Rift Valleys

  • Seafloor spreading occurs at mid-ocean ridges, where molten rock adds new oceanic crust, pushing continents apart.
  • The North American and Eurasian plates are drifting apart at about 2.5 centimeters (1 inch) per year due to the Mid-Atlantic Ridge.
  • Rift valleys form when a landmass is splitting apart, such as the East African Rift, which will eventually separate Africa into two continents.

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