Plate Tectonics and Continental Drift Theory
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Questions and Answers

What concept did Harry Hess introduce in relation to oceanic geology?

  • Continental drift
  • Seafloor spreading (correct)
  • Magnetic field reversal
  • Subduction zones

What geological feature is primarily associated with the creation of new ocean crust?

  • Ocean trenches
  • Mid-ocean ridges (correct)
  • Island arcs
  • Continental shelves

What significant evidence supports the theory of seafloor spreading?

  • Glacial deposits in tropical areas
  • Fossil records from volcanic islands
  • Presence of limestone on continental shelves
  • Magnetic striping of ocean floor rocks (correct)

During which historical event was significant mapping of the ocean floor conducted?

<p>World War II (B)</p> Signup and view all the answers

What occurs at mid-ocean ridges according to the seafloor spreading theory?

<p>Molten material erupts and spreads (D)</p> Signup and view all the answers

What type of rocks indicate that molten material has erupted from mid-ocean ridges?

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

What role do trenches play in the seafloor spreading process?

<p>Trenches are zones where ocean crust is destroyed. (D)</p> Signup and view all the answers

What was a consequence of Harry Hess's mapping work during the international Indian Ocean Expedition?

<p>Development of the theory of plate tectonics (C)</p> Signup and view all the answers

What feature makes up the tectonic plates?

<p>Rigid lithosphere (D)</p> Signup and view all the answers

What was the hypothesis proposed by Alfred Wegener?

<p>Continents were once joined as a supercontinent. (D)</p> Signup and view all the answers

Which ocean surrounded the supercontinent Pangaea?

<p>Panthalassa (D)</p> Signup and view all the answers

What is the primary reason the theory of continental drift was initially rejected?

<p>The lack of a strong force for movement. (D)</p> Signup and view all the answers

What does the term 'tectonic' refer to in relation to plate tectonics?

<p>Deformation of the crust (D)</p> Signup and view all the answers

What characterizes the lithosphere?

<p>It is a combination of the crust and upper mantle. (A)</p> Signup and view all the answers

Which of the following was a significant factor in the rejection of the continental drift theory?

<p>Geographical bias in scientific communities. (D)</p> Signup and view all the answers

What type of geological structure is formed from the interaction of tectonic plates?

<p>Volcanoes (D)</p> Signup and view all the answers

What type of boundary occurs when two tectonic plates move towards one another?

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

Which of the following best describes oceanic drilling samples found at ocean ridges?

<p>Younger rocks are found in the center of the ridge. (C)</p> Signup and view all the answers

What is the average rate of tectonic plate movement for most regions?

<p>Approximately 0.60 cm to 10 cm per year (C)</p> Signup and view all the answers

What movement characterizes transform boundaries?

<p>Plates slide past each other horizontally. (A)</p> Signup and view all the answers

Which type of convergent boundary involves oceanic crust colliding with continental crust?

<p>Ocean-Continent boundary (B)</p> Signup and view all the answers

Which of the following is NOT a type of convergent boundary?

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

Which ocean has the fastest average rate of tectonic plate movement?

<p>Pacific Ocean (A)</p> Signup and view all the answers

In which type of convergent boundary do two continental plates collide?

<p>Continent-Continent (A)</p> Signup and view all the answers

Flashcards

Plate Tectonics

The Earth's crust is divided into large plates that move, causing collisions, separations, or friction.

Lithosphere

The rigid outer part of the Earth, including the crust and upper mantle, that tectonic plates are made of.

Asthenosphere

The soft, semi-molten layer beneath the lithosphere.

Plate Movement

Movement of Earth's tectonic plates driven by convection currents in the mantle.

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Continental Drift Theory

The idea that continents were once joined and have drifted apart over time.

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Pangaea

The supercontinent that existed millions of years ago.

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Panthalassa

The large ocean that surrounded the supercontinent Pangaea.

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Tectonic Features

Landforms created by the interaction of tectonic plates.

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Oceanic Drilling Samples

Samples taken from the ocean floor reveal that younger rocks are found at the center of mid-ocean ridges while older rocks are found farther away from the ridge at the trenches.

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Convergent Plate Boundary

Occurs when two tectonic plates move towards each other, causing collisions that result in the formation of mountains, volcanoes, or trenches.

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Ocean-Continent Convergence

Occurs when an oceanic plate collides with a continental plate, leading to the formation of a subduction zone where the denser oceanic plate slides beneath the continental plate.

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Ocean-Ocean Convergence

Occurs when two oceanic plates collide. The older and denser plate subducts beneath the younger plate, forming a trench and volcanic island arcs.

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Continent-Continent Convergence

Occurs when two continental plates collide, creating immense pressure that folds and deforms the crust. This often results in the formation of mountain ranges.

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Divergent Plate Boundary

Occurs when two tectonic plates move apart, creating new crust at mid-ocean ridges or rift valleys.

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Lateral Plate Boundary

Also known as a transform boundary, where two tectonic plates slide past each other horizontally, creating earthquakes.

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Plate Movement Rate

The average speed at which tectonic plates move, ranging from approximately 0.60 cm/yr to 10 cm/yr.

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Seafloor Spreading

The process where new ocean crust is formed at mid-ocean ridges and old crust is pushed away, causing continents to move.

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Mid-Ocean Ridge

A large underwater mountain chain where new ocean crust is formed due to the eruption of molten material from the mantle.

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Rock Pillows

Pillow-shaped rocks found near mid-ocean ridges, formed when molten material erupts and cools quickly in the ocean.

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Magnetic Striping

A pattern of magnetized stripes on the ocean floor, representing the record of Earth's magnetic field reversals.

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What is the evidence for seafloor spreading?

The existence of rock pillows near mid-ocean ridges and magnetic striping patterns on the ocean floor, indicating the creation and movement of new ocean crust.

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Why was the ocean floor mapped during World War II?

To locate enemy submarines hidden in shallow seas, leading to the first detailed maps of the ocean floor.

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Who mapped the ocean floor and proposed seafloor spreading?

American geophysicist and Naval officer Harry Hess, whose work contributed to the development of plate tectonics.

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How does molten material contribute to seafloor spreading?

Molten material rises from the mantle at the mid-ocean ridge, erupts, and spreads out, pushing older rock to both sides of the ridge, driving the process of seafloor spreading.

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Study Notes

Plate Tectonics

  • Earth's crust is divided into 7 major plates that move.
  • Plate movement causes collisions, separations, or friction.
  • Interactions create Earth structures (tectonic features).
  • Tectonic refers to crust deformation due to plate interaction.
  • Lithosphere comprises crust and upper mantle.
  • Asthenosphere underlies lithosphere.
  • Plates move due to underlying mantle convection cells.

Continental Drift Theory

  • Proposed by Alfred Wegener.
  • Continents were once assembled into one supercontinent (Pangaea).
  • Continents drifted apart over geologic time, now spread across the globe..
  • Evidence includes continental shapes fitting together, fossil distribution, and glacial deposits.

Rejection of Continental Drift Theory

  • Many influential scientists were in the Northern Hemisphere, with data mostly from the Southern Hemisphere.
  • Plausible alternative explanations for fossil and glacial distributions existed.

Seafloor Spreading

  • Proposed by Harry Hess (1962).
  • Ocean floors act like conveyer belts, shifting continents.
  • New crust is formed at mid-ocean ridges.
  • Older crust is destroyed at ocean trenches.
  • Molten material from the mantle rises and erupts at mid-ocean ridges.
  • Evidence includes the mountain ranges of mid-ocean ridges, and rock formations that were the result of lava flow and cooling.
  • Newly formed rocks show magnetic reversals.

Types of Plate Movement

  • Convergent: Plates collide.

    • Ocean-continent: Oceanic crust dives below continental crust.
    • Ocean-ocean: One oceanic plate dives below another.
    • Continent-continent: Two continental plates collide.

  • Divergent: Plates move apart.

  • Lateral/Transform: Plates slide past each other.

  • Plate movement rate varies (0.60 cm/yr to 10 cm/yr).

  • Research suggests average rate is around 0.6-10 cm per year.

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Description

Explore the fascinating concepts of plate tectonics and continental drift. This quiz covers the movement of Earth's plates, the evidence for Alfred Wegener's theory, and the rejection of this theory during its time. Test your knowledge on how these geological processes shape our planet's structure.

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