Theory of Plate Tectonics

1
Theory of Plate Tectonics
2
Plate Tectonics

• Is theory that states that pieces of the Earths
  crust are in constant, slow motion.
• This motion is caused by convection currents in
  the mantle.

3

• As the plates move, they collide, pull apart, and
  grind past each other.
• No plate can move without affecting the other
  plates.

4
How do the plates move ?

• 1. Convection currents
• Drags the plates along.
• Convection current cools and sinks.
• Downward movement may cause subduction of plates.
  

5

• 2. Slab push slab pull
• Magma rising along the mid-oceanic ridge exerts
  force that pushes plates away.
• Pull hypothesis force of gravity causes plate
  movement by pulling cooler, denser plate down.
• Both may work with convection currents.

6
Plate boundaries

• Edges of the Earths lithosphere meet at plate
  boundaries.
• Faults breaks in the Earths crust where rocks
  slip past each other form these boundaries.

7
Transform Boundary

• A place where two plates slip past each other,
  moving in opposite directions.
• No crust is created along this boundary.
• Earthquakes occur frequently along these
  boundaries.

8
b
9
Divergent Boundary

• Plates move apart or diverge from each other.
• Most occur along the mid-ocean ridge.
• A rift valley, a deep valley, occurs when
  divergent plates move past each other on land.

10
Divergent Boundary
11
Convergent Boundary

• A place where two plates come together.
• This movement results in a collision of the two
  plates.
• Density of the plates determines which one comes
  out on top.

12
Convergent Boundary
13
Convergent Boundaries

• Results of collision
• Oceanic/oceanic - Subduction occurs
• Oceanic/continental - Oceanic plate sinks
• Continental/continental - Mountain range