9.3 Theory of Plate Tectonics. I. Earth’s Moving Plates A.Earth’s crust is broken into LARGE...

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