C1.7 Changes in the Earth and its atmosphere

Question 1

What are tectonic plates?

Answer 1

Cracked pieces of the earth’s crust and upper part of the mantle

Question 2

Why is there convection currents in the mantle and what to the currents cause?

Answer 2

caused by natural radioactive processes

cause the tectonic plates to move at relative speeds, a few cm a year

Question 3

The mantle is mostly ——– but it is able to————

Answer 3

solid

move slowly

Question 4

What are the only source of minerals and other resources humans need?

Answer 4

the earth’s crust, atmosphere and oceans

Question 5

Describe Wegener’s theory of Continental Drift

Answer 5

He said that about 300 million years ago, there had just been 1 super continent. This landmass broke into smaller chunks which moved apart. He claimed that these chunks (our modern day continents) were slowly drifting apart.

Question 6

What evidence did Wegener have to explain his theory of continental drift?

Answer 6

• Found fossils of very similar plants and animals which were found o opposite sides of the Atlantic Ocean.
• The coastlines of Africa and South America seemed to match like pieces in a jigsaw
• There were matching layers in the rocks in different continents.

Question 7

Why was Wegener’s theory of Continental Drift not accepted for many years?

Answer 7

• Did not have a convincing reason for why it was happening
• Used inaccurate data so made wild predictions
• He was not a proper geologist

Question 8

What did scientists once think the features of the earth’s surface was a result of?

Answer 8

The shrinking of the crust as the earth cooled down after its formation

Question 9

Why cannot scientists accurately predict when earthquakes and volcanic eruptions will occur?

Answer 9

Scientists can not monitor what is happening below the Earth’s crust

not all tremors indicate that a volcano will erupt

plates move suddenly

Question 10

Where do volcanic eruptions and earthquakes occur?

Answer 10

at the boundaries between plate tectonics.

Question 11

Describe the proportions of different gasses in the atmosphere

Answer 11

For 200 million years there has been about:

80% nitrogen

20% oxygen

small proportions of various other gasses including: carbon dioxide, water vapour and noble gasses

Question 12

Describe what happened during the first billion years of the earths existence

Answer 12

• intense volcanic activity
• this released gases that formed the early atmosphere
• water vapour condensed to form oceans

Question 13

Describe one theory about how the ATMOSPHERE was formed

Answer 13

Early period- mainly carbon dioxide and there would have been little or no oxygen gas. (like atmosphere of venus or mars today). There may also have been some water vapour and small proportions of METHANE and AMMONIA

Question 14

Describe one theory how LIFE was formed (primordial soup theory)

Answer 14

• Billions of years ago, earth’s atmosphere contained hydrocarbons and ammonia
• LIGHTENING struck- caused chemical reaction between gases resulting in the formation of amino acids
• amino acids combined to produce organic matter- evolved into simple living organisms

Question 15

What produced the oxygen that is now in the atmosphere?

Answer 15

Plants and algae

through photosynthesis- uses carbon dioxide from atmosphere

Question 16

Where has most of the carbon dioxide from the early atmosphere gone?

Answer 16

carbon became locked up in sedimentary rocks as carbonates and fossil fuels

carbon dioxide dissolves in the oceans

Question 17

What is limestone formed from?

Answer 17

shells and skeletons of marine organisms

Question 18

What do fossil fuels contain?

Answer 18

carbon and hydrocarbons that are the remains of plants and animals.

Question 19

Why can air be fractionally distilled?

Answer 19

As air is a mixture of gases with different boiling points.

gasses can be used for a variety of industrial processes

Question 20

What were the results of the experiment to prove the primordial soup theory and what do they suggest?

Answer 20

They found amino acids were made, but not as many as there are on earth.

Suggests the theory is along the right lines, but isn’t quite right

Question 21

Describe the structure of the Earth

Answer 21

core

mantle

crust - very thin

Question 22

Why does Iceland have volcanoes?

Answer 22

As Iceland is on a boundary between tectonic plates

Question 23

Describe how activity within the earth results in earthquakes

Answer 23

Earthquakes are caused by the sudden movement of the earths tectonic plates

The movement is caused by convection currents in the earths mantle

convection currents are caused by the heat released by radioactive processes in the mantle

Question 24

Describe how volcanic activity during the first billion years of the earths existence led to the formation of oceans

Answer 24

Water vapour was released by the volcanic activity

water vapour condensed to form oceans

Question 25

Give reasons why the percentage of carbon dioxide decreased in the Earth’s early atmosphere

Answer 25

• Carbon dioxide dissolved in oceans
• marine animals used dissolved carbon dioxide to form their shells/skeletons
• plants absorbed carbon dioxide for photosynthesis

Question 26

Why did Miller and Urey use methane, ammonia and hydrogen to reconstruct the earth’s early atmosphere?

Answer 26

Because these gases contain the atoms that are in amino acids

Question 27

Why does the Miller Urey experiment provide weak evidence of how amino acids formed on Earth?

Answer 27

• nobody knows what was in the earth’s early atmosphere- hydrogen, methane and ammonia may not have been in the earth’s early atmosphere
• There may not have been lightening

Miller and Urey only selected gases needed to produce amino acids

Question 28

What is locked up carbon dioxide?

Answer 28

Carbon dioxide from the earths early atmosphere

which formed sedimentary rocks

Question 29

Describe how the percentage of carbon dioxide has changed in the last 4500 million years

Answer 29

decreased rapidly at first

then slowly levels off

Question 30

Should we be concerned about the change in the concentration of carbon dioxide in the atmosphere over the last 200 years?

Answer 30

yes- because percentage is increasing which causes global warming

no- because percentage of carbon dioxide is low compared to millions of years ago.

Question 31

Describe the layered structure of the earth and the relative sizes of the layers

Answer 31

consists of crust, mantle and core

crust is thinner than mantle and core

Question 32

suggest why, in 1920, other scientists thought that Wegener’s theory of continental drift was wrong

Answer 32

• he had little evidence to explain why the plates were moving
• Not well respected as did not have a status- not a proper geologist
• other scientists believed the ‘land bridge’ explained the similar rocks and fossils in africa and south america

Question 33

Deep inside the earth ……………. processes release large amounts of energy. These processes heat up the substances in the Earth’s ………..

Answer 33

radioactive

mantle

Question 34

In the fractional distillation of liquid air, suggest why the air is filtered before the gases are separated

Answer 34

to remove solid/dust particles

Question 35

In the factional distillation of liquid air, suggest why water vapour and carbon dioxide are removed before the gases are compressed and cooled at -200 degrees

Answer 35

as at -200 degrees, water and carbon dioxide are solids

this would therefore block pipes

Question 36

suggest why there are many theories about how life was formed on earth

Answer 36

not enough evidence

Question 37

Explain how the surface of the earth has changed since the earths formation

Answer 37

number of volcanoes reduced because the Earth cooled forming a crust

continents formed because the earth cooled forming a supercontinent which formed the separate continents

Question 38

Describe how and explain why continental drift takes place

Answer 38

• earths crust is divided into tectonic plates
• heat is released by radioactive PROCESSES in the mantle
• causes convection currents in the mantle that move the tectonic plates