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Questions and Answers
What does the Theory of Continental Drift propose about the continents?
The Theory of Continental Drift proposes that continents were once joined together as a single landmass and eventually drifted apart to their current positions.
Why was the Theory of Continental Drift not widely accepted initially?
It was not widely accepted because Wegener could not provide a mechanism for how the continents moved.
Define Plate Tectonics.
Plate Tectonics is the theory that the Earth's lithosphere is divided into large, rigid plates that move relative to each other over the semi-fluid asthenosphere.
List three pieces of evidence that support the Theory of Plate Tectonics.
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What are convection currents and how do they relate to plate movement?
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What is slab pull and how does it influence plate tectonics?
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Describe the three different types of plate boundaries.
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What contribution did Holmes make to the Theory of Plate Tectonics?
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Study Notes
Theory of Continental Drift
- Suggests continents were once a single landmass called Pangaea.
- Continents drifted apart over time to their current positions.
- Initially not accepted due to lack of mechanism for movement proposed by Alfred Wegener.
Theory of Plate Tectonics
- Earth's lithosphere is divided into large, rigid plates.
- Plates move relative to each other, sliding on the semi-fluid asthenosphere.
Evidence Supporting Plate Tectonics
- Fossil distribution indicates similar species existed on different continents.
- Earthquake occurrences provide insight into tectonic activity and boundaries.
- Geographical features such as mountains, volcanoes, and oceanic trenches reflect tectonic interactions.
Mid-Ocean Ridges and Plate Tectonics
- New ocean floor is created at mid-ocean ridges as tectonic plates separate.
- Supports the theory through the observation of seafloor spreading.
Convection Currents
- Movements in fluids caused by temperature or density differences.
- Radioactive processes in Earth's interior drive plate movement.
Slab Pull Process
- Dense oceanic plates subduct beneath continental plates.
- The subduction force pulls the rest of the tectonic plate into the mantle.
Types of Plate Boundaries
- Divergent Boundaries: New crust forms as plates move apart.
- Convergent Boundaries: Crust is destroyed when one plate subducts under another.
- Transform Boundaries: Plates slide horizontally past each other; no crust is produced or destroyed.
Contributions to Plate Tectonics Development
- Wegener: Proposed the initial theory of Continental Drift.
- Holmes: Introduced mantle convection as a driving mechanism behind drift.
- Vine and Matthews: Discovered magnetic stripes on the ocean floor supporting seafloor spreading.
- Glomar Challenger: Conducted deep-sea drilling, providing empirical evidence for Plate Tectonics.
Topographic Features at Plate Boundaries
- Convergent Boundaries: Deep ocean trenches, volcanoes, island arcs, submarine mountain ranges, fault lines.
- Divergent Boundaries: Rift valleys, ocean ridges, fissure volcanoes, underwater mountain chains.
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Description
Explore the Theory of Continental Drift, which explains how continents were once joined and later drifted apart. Learn about Alfred Wegener's proposal and the reasons for its initial rejection, as well as the subsequent development of the Theory of Plate Tectonics that provided a mechanism for these movements.
