Plate Tectonics

Question 1

The Earth’s surface is very ____ - lots of ____ and ____

Answer 1

The Earth’s surface is very crinkly - lots of mountains and valleys

Question 2

What did scientists previously think caused the Earth’s ‘wrinkled’ surface?

Answer 2

The shrinkage of the surface as it cooled down after the Earth was formed

Question 3

What replaced the theory of surface shrinkage?

Answer 3

Continental drift

Question 4

Who came up with the theory of continental drift?

Answer 4

Alfred Wegner

Question 5

What were the 2 main pieces of evidence that pointed to Wegner’s theory of continental drift?

Answer 5

1. Similar organisms’ fossils found on opposite sides of the Atlantic ocean
2. The sides of continents ‘matching up’ in shape and layer
3. Fossils found in ‘wrong’ places

Question 6

How did fossil findings help Wegner come up with the theory of continental drift?

(2)

Answer 6

1. Came across some work listing the fossils of very similiar plants and animals which had been found on opposite sides of the Atlantic ocean
2. Investigating further, he found other cases of this.

Question 7

How did other scientists explain the discovery of fossils of very similar organisms found on opposite sides of the Atlantic ocean?

Answer 7

That there had once been land bridges connecting the continents which animals could cross.

Believed they had ‘sunk’ or been covered over since then

Question 8

Describe Wegner’s 2 findings of ‘matching’ continents

Answer 8

1. The coastlines of Africa and South America seemed to ‘match’ like pieces of a jigsaw
2. There were matching layers in the rocks in different continents

Question 9

What was Wegner’s thinking behind the ‘matching’ of the coastlines of Africa and South America?

Answer 9

Wondered if they had previously been one continent and then split

Question 10

Give an example of fossils being found in the ‘wrong’ places

Answer 10

Fossils of tropical plants being found on Arctic islands, where the current climate would clearly have killed them off

Question 11

When did Wegener publish his theory of continental drift?

Answer 11

1915

Question 12

Describe Wegner’s theory of continental drift

Answer 12

About 300 million years ago there had been just one supercontinent called Pangaea.

It broke into smaller parts which moved apart.

These parts - our modern-day continents - are still drifting apart

Question 13

Was Wegner’s theory accepted straightaway?

Answer 13

NO

It took many years to convince people

Question 14

How did the majority of other scienists react to Wegner’s theory?

Answer 14

They reacted with hostility

Question 15

What were the 4 main reasons scientists at the time opposed Wegner’s theory?

Answer 15

1. Wegner said continents were ‘ploughing through’ the sea bed, and their movement was caused by tidal forces and the Earth’s rotation
   - other geologists said this was impossible - 1 said it would stop the Earth’s rotation (which it hadn’t)
2. Wegner had used innacurate data - wild predictions about speed of continental drift
3. Wegner was an astonomist, not a ‘proper’ geologist
4. Wegner was quite young - seen as inexperienced and not respected

Question 16

What happened in the 1950s concerning continental drift?

Answer 16

In an investigation of the ocean floor, new evidence found to support it.

Main idea = correct

Question 17

When was the theory of continental drift accepted as the main theory?

Answer 17

In the 1960s

Question 18

What is our belief concerning continental drift today?

Answer 18

The Earth’s crust is made up of several parts called tectonic plates which move around, and that colliding plates push the land up to create mountains