Vocabulary

• Plate• Scientific theory• Plate tectonics• Fault• Transform boundary • Diverent boundary• Rift valley• Convergent boundary

The Theory ofThe Theory of Plate TectonicsPlate Tectonics

Chapter 1 Section 5Chapter 1 Section 5

What isWhat is Plate TectonicsPlate Tectonics??

In 1965, J Tuzo Wilson put together Wegner’s theory of continental drift and Hess’ theory

about sea-floor spreading into one big theory- Plate Tectonics

Plate TectonicsPlate Tectonics is the theory is the theory that states that pieces of that states that pieces of

Earth’sEarth’s lithospherelithosphere are in are in constant, slow motion, driven constant, slow motion, driven byby convection currentsconvection currents inin the the

mantle.mantle.

Confused?Confused?

I’ll explain. I’ll explain.

These pieces of the lithosphere These pieces of the lithosphere are calledare called platesplates or or tectonic tectonic platesplates..

TheThe platesplates are always are always moving in slow motion.moving in slow motion.

So what moves them?So what moves them?

Scientists think that Scientists think that convection currentsconvection currents inside the mantle do!inside the mantle do!

Plate TectonicsPlate Tectonics is the theory is the theory that states that pieces of that states that pieces of

Earth’sEarth’s lithospherelithosphere are in are in constant, slow motion, driven constant, slow motion, driven byby convection currentsconvection currents inin the the

mantle.mantle.

As the plates move As the plates move around they collide, around they collide, pull apart and grind pull apart and grind

past each other!past each other!

Plates collide Plates collide atat

convergent convergent zoneszones

The Cascades were formed at aThe Cascades were formed at a convergent zoneconvergent zone

Many volcanic islands are Many volcanic islands are formed atformed at convergent zonesconvergent zones..

So were the Himalayas!So were the Himalayas!

Do you see how?Do you see how?

Plates move apart, Plates move apart, or divide, ator divide, at

divergent divergent boundariesboundaries..

The mid- ocean ridge is a The mid- ocean ridge is a divergent boundarydivergent boundary..

Plates slide past Plates slide past each other ateach other at

transform transform boundariesboundaries..

Crust is neither Crust is neither created or destroyed created or destroyed at at transform transform boundariesboundaries..

3 boundaries are 3 boundaries are convergentconvergent, , divergentdivergent and and transformtransform!!