C1.7 Changes in the Earth and its Atomosphere

Question 1

What is the modern theory of how mountains were formed?

Answer 1

The earth’s surface is split up into big chunks called tectonic plates, and mountains are formed when these tectonic plates collide

Question 2

Who created the theory of ‘continental drift’?

Answer 2

Alfred Wegner

Question 3

What was the theory of continental drift?

Answer 3

That about 300 million years ago, there had been just one ‘supercontinent’ called Pangaea - which eventually drifted apart into smaller chunks which are now their own continent

Question 4

What was Wegner’s evidence for continental drift? (3)

Answer 4

Fossils of similar plants and animals were found on the opposite sides of the Atlantic ocean, he noticed that the coastlines of south America and Africa fit together like a jigsaw and fossils were found in areas where that particular organism would not be able to survive

Question 5

Reactions to Wegner’s was mostly hostile, why? (3)

Answer 5

Wegner couldn’t explain how the continents moved - he believed their movement was caused by tidal forces, but other geologists said that was impossible, also, land bridges explained a lot of Wegner’s evidence and Wegner wasn’t a geologist, he studied astronomy

Question 6

Why did the theory of land bridges prove Wegner’s theory wrong?

Answer 6

Land bridges between continents meant that animals could easily move between continents, (explaining why fossils were found) and over time they sunk or were covered

Question 7

When did Wegner’s theory get some appreciation?

Answer 7

In the 1950s, when the ocean floor could be investigated - he wasn’t completely right, but his main idea was right, and by the 1960s tectonic plates were discovered

Question 8

What are the layers of the earth, from outside in? (4)

Answer 8

Atmosphere, crust, mantle and an iron and nickel core

Question 9

What are the properties of the earth’s crust?

Answer 9

It’s the bit we live on, it’s very thin and is surrounded by the atmosphere

Question 10

What are the properties of the earth’s mantle?

Answer 10

It has all the properties of a solid, except that it can flow very slowly in convention currents - due to the large amounts of heat produced by radioactive decay in the core

Question 11

Where do humans get our resources from? (3)

Answer 11

The crust, oceans and the atmospheres

Question 12

What are tectonic plates?

Answer 12

Large pieces of rock which ‘float’ on the mantle

Question 13

How do tectonic plates move?

Answer 13

Due to convention currents from the mantle, the plates drift

Question 14

How quickly do tectonic plates move? What happens if they move quickly?

Answer 14

They move a few centimetres a year, if they move suddenly they can cause earthquakes

Question 15

Why is it so difficult to predict an earthquake?

Answer 15

Because we can’t see what’s happening deep underground

Question 16

Why are predictions for earthquakes ignored by people? (4)

Answer 16

Because predictions don’t have an exact date, you can’t predict the strength of the earthquake - many earthquakes cause little or no damage, the exact location of an earthquake isn’t accurate and you can’t stop an earthquake, you can only evacuate, which can be expensive so people want to be sure that there is an earthquake before leaving

Question 17

How are volcanic eruptions predicted?

Answer 17

Before an eruption molten rock rises up into chambers near the surface which causes mini-earthquakes near the volcano - but sometimes molten rock cools down instead of erupting, so it can be a false alarm

Question 18

What are the main gases in the atmosphere? What else is there?

Answer 18

Oxygen (20%) and nitrogen (80%) - but there’s also carbon dioxide, water vapour and noble gases

Question 19

Before an atmosphere was formed, what was the surface of the earth like?

Answer 19

Molten - any formation of an atmosphere just boiled away into space

Question 20

What is theory for how oceans were formed?

Answer 20

It is thought that the atmosphere was once mainly CO2* and water vapour - and as the earth cooled, the water vapour condensed to form oceans

Question 21

If levels of CO2* were so high, why is there such a low % of CO2* now?

Answer 21

Due to the absorption by ocean and the absorption by plants and algae - photosynthesis produces oxygen, which is why levels of oxygen are so much higher now

Question 22

How was the carbon that was once in our atmosphere, ‘locked away’?

Answer 22

In fossil fuels - which is made is made of the remains of plants and animals

Question 23

How does increasing levels of carbon dioxide affect the earth?

Answer 23

Global warming - an increase in the average temp. on earth, and acidity in oceans - the oceans absorb the carbon dioxide which increases their acidity, this can lead to the death of marine animals

Question 24

Why is air fractionally distilled?

Answer 24

To get a variety of products that can be used as raw materials in industry

Question 25

How are impurities removed from the air (in the fractional distillation of air)?

Answer 25

The air is first filtered to remove dust. It is then cooled to -200C and becomes liquid - here, carbon dioxide freezes so it can be removed

Question 26

Why is the fractional distillation of air possible?

Answer 26

Because different gases in air have different boiling points so they will condense at different temperatures

Question 27

How are the different gases from air extracted from a fractionating column?

Answer 27

Once the air vaporises, the different gases can be extracted at the different levels where they condense

Question 28

What is the primordial soup theory?

Answer 28

Lightning struck earth which had an atmosphere rich in nitrogen, hydrogen, ammonia and methane. This caused a chemical reaction which formed amino acids - these then collected to form a body of water out which life gradually crawled

Question 29

Who tested the primordial soup theory?

Answer 29

Miller and Urey

Question 30

Why will there always be a mystery of life?

Answer 30

Because we are unable to know exactly what happened 3 billion years ago - we can only guess