CONTINENTAL DRIFT THEORY

He was a key figure in changing ideas about the earth’s surface. In 1912, he proposed that all the continents were once joined in a single supercontinent, called Pangaea.

alfred wegener

He suggested that pangaea began to break up about 200 million years ago and the pieces drifted apart to form the present day continents.

alfred wegener

At the time, Wegener’s theory of __________ was dismissed by geologists because he could not provide a convincing explanation for how the continents were able to move.

continental drift

What are the evidences of continental drift?

fit of the continents, fossil evidence, ancient mountain ranges, past climate evidence

The theory of __________ was developed over time due to the combined efforts of many of pioneering scientists.

continental drift

Seafloor spreading was proposed by _______ to explain continental drift.

Harry Hess

In ______ two oceanic plates move away from each other resulting in the formation of new oceanic crust

seafloor spreading

If you look at the map of the world, you may notice that some of the continents could fit together like pieces of a ______.

puzzle

The key geological theory that explains how the Earth’s surface changes now and has changed in the past is called ________.

plate tectonics

The explanation for how the continents move came from observations of seafloor spreading and other effects. In 1967, these ideas were linked in the _________.

theory of plate tectonics

According to this theory, the earth’s crust is like a jigsaw puzzle made up giant sections called _________.

tectonic plates

How many major tectonic plates are there?

7

The area where two tectonic plates meet is called a _________. Mountains, volcanoes and oceanic trenches are formed at plate boundaries, and earthquakes are more likely to occur here.

plate boundary

there are three types of plate boundary: ______, ______, _______. Each type is characterized by how the plates and the geological effects of this movement.

constructive, destructive, conservative

• the earth’s surface is made up of several huge tectonic plates that are continually moving
  the ocean floors

• the ocean floors are continuallly moving, spreading from the centre and sinking the edges

• earthquakes and volcanoes occur at plate boundaries, where the tectonic plates meet.

• convection currents in the mantle move the tectonic plates on the earth’s surface.

the key points of plate tectonics

what are the three styles of convergent plate boundaries

• continent-continent collision

• continent-oceanic crust collision

• ocean-ocean collision

forms mountains (european alps, himalayas)

continent-continent collision