Plate Tectonics: Movement and Structure

• Plate tectonics is the theory that the Earth's surface is broken into large crustal pieces called plates.
• These plates move on a softer layer called the asthenosphere, the upper part of the mantle.
• Plate tectonics explained continental drift and tied together geological observations.

Plate Thickness and Boundaries

• Continental plates are up to 150 km thick.
• Oceanic plates average about 5-10 km thick.
• Plate boundaries differ from continental boundaries and can be underwater.
• The North American plate extends from the mid-Atlantic Ocean to North America's west coast.

Causes of Plate Movement

• Heat from Earth's core causes convection cells in the mantle, moving the plates.
• Radioactive decay of uranium and other elements generates heat
• The heat softens the rock, allowing it to flow over thousands of years.
• Hot rock rises toward the crust, while cooler rock sinks back toward the core, forming convection currents.

Additional Causes

• Convection currents encounter the crust, causing plate movement.
• Plate movement leads to plates colliding, sliding, or being pushed under each other.
• Ridge push contributes to plate movement.
• Plates higher at the spreading center flow downhill due to gravity.
• Ridge push forces new crust up at the fault, and subsequent movement.
• Oceanic crust can be forced under another plate at converging boundaries.
• Deep ocean trenches indicate where one plate slides under another.
• As a plate slides under, gravity helps pull it along, adding to the force.
• Trenches are created when oceanic plates are forced under other plates.

Explore the theory of plate tectonics, explaining that Earth's surface is divided into large crustal plates. Learn about plate thickness, boundaries, and the underlying causes of plate movement, including mantle convection and radioactive decay. Discover how these plates drift.