- Slides: 23
Theory of Plate Tectonics
Continental Drift • The geological theory by Alfred Wegner that states that Earth’s continents were once ONE large landmass “Pangea” and over time the continents slowly moved apart. • Evidence. . . ▫ Shape of the Earth’s continents They look like they fit together like pieces of a puzzle
Continental Drift • This theory was NOT CORRECT!!
Plate Tectonics • The geological theory by Tuzo Wilson that states that pieces of Earth’s lithosphere are in constant slow motion. • Evidence ▫ The SAME FOSSILS on different continents ▫ Magnetic patterns found on the ocean floor at along a mid-ocean ridge.
Plate Tectonics – Lithosphere • Lithosphere ▫ Top layer of the Earth which contains the “plates” • Asthenosphere ▫ Partially molten layer of Earth right below the Lithosphere. ▫ There are convection currents in the Asthenosphere that slowly move Earth’s plates (the Lithosphere)
Lithosphere and Asthenosphere Convection Currents in the asthenosphere
Earth’s Plates – Boundary Map
3 Types of Boundaries 1. Transform 2. Divergent 3. Convergent
Transform Boundaries • 2 plates slide past each other, moving in opposite directions • Along these boundaries, crust is neither created or destroyed • Earthquakes occur here • Faults are created
Divergent Boundaries • 2 plates slide apart or diverge • Forms rift valleys and mid-ocean ridge • Sea-floor spreading occurs here
Divergent Boundaries Sea-Floor Spreading Rift valley
Convergent Boundaries • 2 plates slide together or converge • Results in a collision ▫ Denser crust will be on the bottom (oceanic crust) • Usually forms mountains, volcanoes, trenches, and a subduction zone
Convergent Boundaries Subduction Zone The denser plate (oceanic) will go into the Earth Volcano Trench
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Plate Tectonics vs. Continental Drift Plate Tectonics Plates are moving. Theory by: Tuzo Wilson Continental Drift Move Continents are moving. Theory by: Alfred Wegner