Ch.5.less.2.what happens when earth plates move

What happens

when earth plates move?

Ch.5: Less.2:

Alfred Wegener

German Geologist

(Geologist is a scientist who

studies rocks to find about earth’s

history and structure)

Wegener’s Hypothesis

• In 1912 Alfred Wegener proposed the theory of continental drift.

• Continental drift theory: States that the continents once formed a single land that broke up, and drifted to their current location today.

• Wegener used several different types of evidence to support his hypothesis

PANGAEAWhen all the continent where 1 landmass, it was called:

Continental Drift Theory

Wegener used several

different types of evidence to

support his hypothesis

1) Wegener noticed that the continents fit each other like jigsaw puzzle pieces (as time passed some force pulled the puzzle pieces apart)

2) Scientists found that the mountains in south America and Africa had the same types of rocks and the same age.

3) Similar fossils where found on different continents.

Mesosaurus (a fresh water reptile)The mesosaurus fossil was found in South America and Africa (it cannot swim in the ocean)

Fossil Evidence

What forces caused

the continenta

l drift?

Scientists came up with the “Plate tectonics theory”

“Plate tectonics theory” States that the lithosphere is made of huge plates of solid rock and these plates slide on the slippery surface of the asthenosphere causing the continents on them to move.

There are 3 types of tectonic plate movement.

Divergent Convergent Transform

1) Divergent tectonic plates

Magma (hot melted rocks) from the mantle moves upwards pushing the plates apart causing tension (push).

This push causes:1) Ocean floor spreading and 2) mid ocean ridges.

(Because the continents are resting on these plates they also move apart)

2) Convergent tectonic plates

When the plates are pushed into each other, they form a compression force.

Compression causes:1) Folded mountains(earth crust is folded) and

Example.Himalayas are folded mountains (formed when Asia and India collided together)

3) Transform tectonic plates

When the plates are rub together, they form a shear force.

The break in the earth’s crust where the plates rub against each other is called

faults.Break in the crust at faults cause:

1) Fault block mountains

Sierra Nevada Mountains (U.S.A)