Continental Drift Theory Quiz

Study Notes

Proposed by Alfred Lothar Wegener in 1912, suggesting continents were once a single supercontinent called Pangaea, meaning "All Earth."
Pangaea began breaking apart approximately 200 million years ago, leading to the formation of present-day continents.

From Rocks:
- Fossils of Mesosaurus, a freshwater reptile, found on separate continents support the theory.
- Rock formations in Africa and South America align, indicating historical connection.
From Fossils:
- Fossilized leaves of Glossopteris, an extinct plant, found across Southern Africa, Australia, India, and Antarctica, showing these continents were once joined.
- Large seeds of Glossopteris could not have crossed vast oceans by wind or waves.
Coal Deposits and Ancient Climates:
- Coal beds formed from decomposed swamp plants discovered in regions now under different climates, including Antarctica, suggesting it once had a tropical climate near the Equator.
Evidence of Glaciation:
- Glacial striations found in South America, Africa, India, and Australia indicate past glacial activity, where large boulders scratched surfaces beneath glacial movements.

Wegener's estimated continental motion speed of 250 cm/year was deemed too rapid.
He failed to provide a plausible mechanism for the movement of continents.

Mantle: Linked to the Earth's less dense molten material which rises and sinks.
Asthenosphere: A plastic-like layer in the upper mantle where lithospheric plates float and move, not a liquid but a viscoelastic solid.
Magma: Hot molten rocks formed beneath the Earth’s surface.

Convection Currents: Facilitate lithospheric plate movement through energy transfer in the asthenosphere.

Core: Innermost layer generating heat for the mantle.
Lithospheric Plates: Massive slabs of solid rock comprising continental and oceanic lithosphere.

Radioactive Decay: Contributes significant heat from decay of elements like uranium and thorium, influencing heat distribution.
Sources of Heat: Include primordial heat, frictional heating from core material, and heat from radioactive decay.
Convection Current: Warm materials rise, cool and sink, creating a loop that contributes to lithospheric plate movement.
Ridge Push and Slab Pull: Movements caused by rising and sinking magma lead to sea-floor spreading and subduction.

Proposed by Arthur Holmes, suggesting heated mantle material becomes less dense and rises, while cooled material sinks, creating a conveyor belt effect that can both separate and rejoin continents.