C1.7 Changes in the Earth and its atmosphere

Question 1

What was Alfred Wegener’s theory?

Answer 1

Continental drift, at one time all the continents were joined together but over time they have slowly drifted apart to form the modern day continents we know today

Question 2

What was his evidence of continental drift?

Answer 2

He found fossils of very similar plants and animals on opposite sides of the atlantic ocean. He also found other cases of this. Additionally he notice that Africa and South America seemed to fit together like a jigsaw. Their were matching rocks in different continents. Some fossils were found in the wrong continents, i.e. where they wouldn’t have survived.

Question 3

What was the name Wegener gave to the original ‘supercontinent’?

Answer 3

Pangaea

Question 4

Why was Wegener’s theory rejected?

Answer 4

Geologists thought it was impossible and one calculated that the forces needed to move the continents would have stopped the earth rotating. Wegener had used inaccurate data in his calculations. Wegener wasn’t a ‘proper’ geologist

Question 5

By when was the theory accepted?

Answer 5

1960’s

Question 6

Which part of the earth do we live on?

Answer 6

The crust

Question 7

What are the properties of the crust?

Answer 7

It is very thin. From 5km to 50km. It is surrounded by the atmosphere

Question 8

What is below the crust?

Answer 8

The mantle

Question 9

What are the properties of the mantle?

Answer 9

It has the properties of a solid except it can flow very slowly. Radioactive decay takes place, producing a lot of heat

Question 10

What occurs in the mantle?

Answer 10

Convection currents

Question 11

What is at the centre of the earth?

Answer 11

The core

Question 12

What is the inner core made of?

Answer 12

It is made up of solid iron and nickel

Question 13

What is the outer core made up of?

Answer 13

It is made up of liquid iron and nickel

Question 14

Which part of the earth is the hottest?

Answer 14

The inner core, with temperatures up to 5,500 degrees celsius

Question 15

How thick is the mantle?

Answer 15

Approximately 2,900 km

Question 16

What are the crust and the upper part of the mantle cracked into?

Answer 16

Tectonic plates which float on the mantle

Question 17

Why do tectonic plates drift?

Answer 17

Because of convection currents in the mantle. The large amounts of heat released through radioactive processes cause convection currents to form

Question 18

What causes convection currents in the mantle?

Answer 18

The heat released from radioactive processes causes the mantle to heat at the bottom. As heat rises the mantle also slowly rises until it loses energy and cools, causing it to fall back down again. This forms a steady current of movement in the mantle, causing the tectonic plates to move

Question 19

How much do tectonic plates move each year?

Answer 19

A couple of centimetres

Question 20

What happens when the tectonic plates move very suddenly?

Answer 20

An earthquake

Question 21

Where do volcanoes and earthquakes often occur?

Answer 21

At the boundaries between two tectonic plates (fault lines)

Question 22

Are volcanoes and earthquakes easy to predict?

Answer 22

No, they are very sudden and disastrous. However there are some methods of detection but they can sometimes lead to a false alarm

Question 23

How was the atmosphere formed?

Answer 23

Volcanoes gave out a lot of gas

Question 24

What was the early atmosphere?

Answer 24

Mostly CO2, water vapour and small amounts of methane and ammonia

Question 25

How were the oceans formed?

Answer 25

When the water vapour condensed

Question 26

What is the proportions of different gases in the current atmosphere?

Answer 26

80% Nitrogen
20% Oxygen
Small proportions of other gases such as carbon dioxide, water vapour and noble gases

Question 27

What was Earth’s surface originally like?

Answer 27

Molten and so hot any atmosphere ‘boiled away.’ Eventually it cooled down a bit and a thin crust formed

Question 28

Why did green plants and algae evolve over the earth?

Answer 28

The were happy in the CO2 atmosphere

Question 29

What happened to the early CO2?

Answer 29

A lot of it was dissolved into the ocean and the green plants and algae absorbed some of the CO2, producing O2 by photosynthesis

Question 30

What happened to the dead plants and algae?

Answer 30

It was buried under layers of sediment along with other dead organisms. The carbon and hydrocarbons inside them became locked up in sedimentary rocks as insoluble rocks and fossil fuels

Question 31

What happens when we burn fossil fuels?

Answer 31

The ‘locked-up’ carbon is released and the concentration of CO2 in the atmosphere increases

Question 32

What happened as a result of the build-up of oxygen?

Answer 32

Many of the earlier organisms died as they could not tolerate it, but other more complex organisms were allowed to evolve

Question 33

What did the oxygen create

Answer 33

The Ozone, which blocks harmful rays

Question 34

How much carbon dioxide is there in the atmosphere now?

Answer 34

Very little

Question 35

What did the oceans act as?

Answer 35

A reservoir for carbon dioxide

Question 36

Give an example of an insoluble carbonate

Answer 36

Limestone, formed by shells and skeletons of marine organisms

Question 37

Name the theory surrounding how life was formed by interaction between hydrocarbons, ammonia and lightning

Answer 37

The primordial soup theory

Question 38

What is the primordial soup theory?

Answer 38

The earth’s atmosphere was once rich in nitrogen, hydrogen, ammonia and methane. Lightning struck, causing a chemical reaction between the gases resulting in the formation of amino acids. The amino acids collected a a ‘primordial soup’ and gradually combined to produce organic matter which eventually evolved into simple living organisms

Question 39

Who carried out an experiment to prove this theory?

Answer 39

Miller and Urey

Question 40

What experiment did Miller and Urey do?

Answer 40

They sealed the gases in their apparatus, heated them and applied an electrical charge for a week. They found that amino acids were made, but not quite as much as there are on earth

Question 41

Can we fractionally distill air?

Answer 41

Yes as the mixtures of gases have different boiling points. By fractionally distilling air we can get a variety of products for use in the industry

Question 42

What is the process of Fraction Distillation with air?

Answer 42

1. The air is filtered to remove dust
2. It is then cooled to -200 degrees and becomes a liquid
3. During cooling the water vapour condenses and is removed
4. Carbon dioxide freezes and is removed
5. The liquified air then enters the column and is heated slowly
6. The remaining gases are separated by fractional distillation. (Oxygen and argon come out together so another column is used to separate them)