Plate Tectonics and Plate Boundaries

Plate Tectonics Theory

• The theory of plate tectonics states that the Earth's lithosphere is broken into several large plates that float on the more fluid asthenosphere.
• These plates are in continuous motion, sliding over the more fluid mantle below.

Types of Plate Boundaries

• There are three types of plate boundaries: convergent, divergent, and transform boundaries.

Convection Currents

• Convection currents are formed within the mantle as hot material rises to the surface, cools, and then sinks back down.
• This circulation of hot material is driven by heat from the Earth's core.

Driving Force behind Plate Movement

• The driving force behind plate movement is convection currents in the mantle.

Plate Boundary Interactions

• Convergent boundaries are formed when two plates collide, resulting in subduction or collision.
• Divergent boundaries are formed when two plates move apart, resulting in the creation of new crust.
• Transform boundaries are formed when two plates slide past each other horizontally.

Convergent Boundaries

• At a convergent boundary, one plate is forced beneath another (subduction) or the two plates collide.
• When an oceanic plate sinks under another plate, it encounters increasing heat and pressure, causing it to melt and release magma, resulting in volcanic activity.
• When oceanic crust collides with continental crust, the denser oceanic crust is pushed beneath the continental crust.

Divergent Boundaries

• At a divergent boundary, new crust is created as magma rises from the mantle and solidifies.
• A sign of a divergent boundary is the presence of shield volcanoes, linear cracks, and fault lines.

Transform Boundaries

• At a transform boundary, two plates slide past each other horizontally, resulting in faulting and earthquakes.
• The San Andreas Fault in California is a famous example of a transform boundary.

Crust Types

• There are two types of crust: continental crust (thick and buoyant) and oceanic crust (thin and dense).

Faults

• A fault is a crack or break in the Earth's crust where rocks on either side have moved past each other.