9.3 Theory of Plate Tectonics

I. Earth’s Moving PlatesA.Earth’s crust is broken into LARGE

pieces called “plates”1. Plates contain continents and oceans 2. Faults = cracks between each plate

a. separate each plate

B.Cause of Movement: convection currents in the mantle

C. Effect: plates move 5 cm per year 1. Results: earthquakes, volcanoes,

mountains

9.4: MECHANISMS OF PLATE MOTION

I. CAUSE OF PLATE MOTIONA.Convection Currents 1.Movement of material due to

differences in densitya. Warm material less dense &

risesb. Cool material is more dense &

sinks2.Occurs in the mantle3.Heat source: the core (middle

of Earth)4.Plates are the “top” of the

currentshttps://www.youtube.com/watch?v=kwfNGatxUJI

II. MANTLE CONVECTION

A.Downward movement: 1. Slab-pull: gravity pulls old crust

into the mantle2.Ridge-push: crust slides below into

the mantleB.Upward movement:

1.Mantle plumes: rising column of mantle rock to the crusta. Creates "hot spots“ & volcanoes

https://www.youtube.com/watch?v=ryrXAGY1dmE