C1.7 Changes in the earth and its atmosphere

Question 1

What are the only sources of minerals and resources that humans need?

Answer 1

• Earth’s crust
• Earth’s atmosphere
• Earth’s oceans

Question 2

What does the earth consist of?

Answer 2

• A core made of nickel and iron (why we have magnetic poles)
• A very thin crust (5km - 50km)
• Mantle with all the properties of a solid but it can flow very slowly

Question 3

What is earth’s crust and upper part of the mantle divided into?

Answer 3

Large pieces - tectonic plates

Question 4

Why do tectonic plates move a few centimetres a year?

Answer 4

• Radioactive decay in the core releases heat
• This causes convection currents in the mantle
• This causes the tectonic plates of the crust to move

Question 5

Explain the theory of continental drift.

Answer 5

• 300 million years ago, earth was one supercontinent called Pangea.
• Pangea broke into smaller chunks which moved apart to their current positions and are still drifting

Question 6

How came up with the theory of continental drift?

Answer 6

Albert Wegner

Question 7

What was Albert Wegner’s evidence for continental drift?

Answer 7

• Africa and South America fit together like a jigsaw

- Fossils and rock types matched on opposite sides of the world (people thought this was due to land bridges)

Question 8

Explain the raisin/shrinking earth theory.

Answer 8

Mountain ranges were forced up by the wrinkling process of the earth as it was cooling down from the Big Bang

Question 9

Give 3 reasons why Wegner’s theory was not accepted.

Answer 9

• He didn’t have a proper reason for the driving mechanism
• He wasn’t a “proper” geologist - he studied astrology
• He used inaccurate data in his predictions

Question 10

What can happen at boundaries between tectonic plates?

Answer 10

• Earthquakes

- Volcanic eruptions

Question 11

What has the atmosphere of earth been made up for the past 200 million years?

Answer 11

• 80 % nitrogen
• 20% oxygen
• Small proportions of carbon dioxide, water vapour and noble gases

Question 12

Where did earth’s early atmosphere come from?

Answer 12

• During the first billion years there was intense volcanic activity
• This activity released gases forming earth’s early atmosphere
• Water vapour condensed to form the oceans

Question 13

What was earth’s early atmosphere like?

Answer 13

Mostly carbon dioxide with some water vapour and traces of methane and ammonia

Question 14

How did carbon dioxide from earth’s early atmosphere decrease?

Answer 14

• Plants evolved and absorbed carbon dioxide in photosynthesis
• Carbon dioxide was locked up in fossil fuels and sedimentary rocks as carbonates
• Carbon dioxide was dissolved in oceans

Question 15

How did oxygen increase from earth’s early atmosphere?

Answer 15

Plants released it in photosynthesis

Question 16

What did the oxygen increase from earth’s early atmosphere cause?

Answer 16

• The ozone layer, blocking harmful rays from the sun and allowing more complex organisms to evolve

Question 17

What causes eruptions/earthquakes at plate boundaries?

Answer 17

A sudden release of strain energy

Question 18

Why are earthquakes hard to predict?

Answer 18

• Scientists can’t be certain what is happening under the crust
• Scientists can’t be certain where the forces/pressure are building up
• Scientists can’t be certain of the force measurement

Question 19

Who carried out an experiment to prove the primordial soup theory?

Answer 19

Miller and Urey

Question 20

What did Miller and Urey find about the primordial soup theory?

Answer 20

Amino acids were made, but as many as there are on earth.

Question 21

Explain the primordial soup theory

Answer 21

• Billions of years ago, the earth’s atmosphere was rich in nitrogen, hydrogen, ammonia and methane
• Lightning struck, causing a chemical reaction that produced amino acids
• They eventually combined to form organic matter which evolved into organisms

Question 22

What is the other theory for how life began?

Answer 22

Life came to earth on a meteorite crashing into earth

Question 23

How did nitrogen increase from earth’s early atmosphere?

Answer 23

• Ammonia reacted with oxygen to produce it

- Bacteria released it

Question 24

How can we get a variety of gases to use in industry?

Answer 24

By fractionally distilling our air

Question 25

Explain how air is fractionally distilled.

Answer 25

• Air is filtered to remove dust
• It is then cooled to around -200c degrees and becomes a liquid with a high pressure
• Pressure is released so air expands rapidly causing temperature to decrease further
• Carbon dioxide and water solidify and are removed
• The liquefied air is heated up as it enters the fractionating column
• The remaining gases are separated by fractional distillation - the lower boiling point gases boil off first and are separated
• Oxygen and argon come out together so another column is used to separate them

Question 26

What is the effect of increased carbon dioxide levels on the climate and oceans?

Answer 26

• An increase in carbon dioxide is causing global warming
• Oceans are a natural store of carbon dioxide as they absorb it from the atmosphere but the extra carbon dioxide we’re releasing is making them too acidic.
• This causes shellfish and coral to die, and us not being able to store CO2 in the future

Question 27

Why are carbon dioxide levels increasing?

Answer 27

• The world is becoming more industrialised

- So more fossil fuels are being burnt in power stations and in car engines