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

continental

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)