Our Changing Planet

Question 1

Describe the crust

Answer 1

• Between 5km and 70km thick
• Very thin layer
• Top layer of the Earth

Question 2

Describe the mantle

Answer 2

• 3000km thick
• Almost entirely solid but parts can flow very slowly
• Goes almost halfway to the centre of the Earth

Question 3

Describe the core

Answer 3

• About half the diameter of the Earth
• Has a high proportion of the magnetic metals iron and nickel
• Has a liquid outer part and solid inner part

Question 4

Describe the atmosphere

Answer 4

• Surrounds the Earth
• Most of the air is within 10km of the surface
• Most of the atmosphere is within 100km of the surface

Question 5

Name the layers of the Earth

Answer 5

• Inner core
• Outer core
• Mantle
• Crust
• Atmosphere

Question 6

What are techtonic plates?

Answer 6

The huge slabs of rock that make up the Earth’s crust and the top part of its mantle

Question 7

How and why do techtonic plates move?

Answer 7

• Move a few centimetres each year due to convection currents in the mantle
• These are caused by the energy released by the decay of radioactive elements heating up the mantle
• Where the plates meet, huge forces build up. Eventually, the rocks give way, changing shape or moving suddenly. This causes earthquakes, volcanoes, or montains to form

Question 8

Why can scientists not predict when and where earthquakes will occur?

Answer 8

Because they still do not know enough about what is happening inside the earth

We do not have good enough data/models to make accurate predicitions

Question 9

Describe the theory of continental drift and why there was opposition to it

Answer 9

• Put forward by Alfred Wegener in 1915
• Other scientists at the time did not accept his ideas, mainly because he couldn’t prove why
• They believed the Earth was shrinking as it cooled
• In the 1960s, scientists found new evidience and plate techtonics was developed

Question 10

How do scientists think the Earth’s atmosphere has changed over time?

Answer 10

• Scientists think the Earth was formed 4.5 billion years ago
• In the 1st billion years it was covered with volcanoes which released CO₂, water vapour, and nitrogen
• As the Earth cooled, most of the water vapour condensed to form oceans. This meant that the early atmosphere was mostly CO₂ with some water vapour. Some scientists believe there was also some nitrogen and possible amonia + methane
• In the next 2 billion years, bacteria, algae, and plants evolved. Algae and plants used CO₂ for photosynthesis and released oxygen
• As the number of plants increased, the amount of CO₂ decreased and the amount of oxygen increased

Question 11

Why are we not sure how life began?

Answer 11

There is insufficient evidence / lots of theories but no proof

Question 12

What was the Miller-Urey experiment and what did it show?

Answer 12

• Conducted in 1952 by Miller + Urey. Based on what scientists at the time was in the early atmosphere
• Used a mixture of water, ammonia, methane, and hydrogen and a high voltage spark to simulte lighting
• After a week they found that amino acids, the building blocks for proteins, had been produced
• Showed that lighting could have triggered reaction to create amino acids which would then create proteins, and from there complex life (plants)

Question 13

What are the other theories about how life on Earth developed?

Answer 13

• Since the 1950s, theories about what was in the early atmosphere have changed, but amino acids have never been able to be produced using a different combination of gasses to Miller and Urey
• One theory suggests that these organic molecules formed a ‘primordial soup’ and that the amino acids in this mixture of gasses combined to make proteins
• Many other theories have been proposed, but there is not enough evidence

Question 14

How do scientists think life on Earth began?

Answer 14

• The plants that produced the oxygen in the atmosphere probably evolved from simple organisms like plakton and algae in the ancient oceans
• But we don’t know how the molecules of the simplest living things were formed
• No one knows for sure because there’s not enough evidence

Question 15

Where did most of the CO₂ from Earth’s early atmosphere go?

Answer 15

• Plants took up much of the CO₂ in the Earth’s early atmosphere
• Animals ate the plants and much of the carbon ended up in plant + animal remains as sedimentary rock and fossil fuels
• Limestone was formed from the shells and skeletons of marine organisms
• Fossil fuels contain carbon and hydrogen from plants and animals
• CO₂ dissolved in oceans and some probably formed insoluble carbonate compounds that were deposited on the seabed to become sedimentary rocks

Question 16

How long ago did the proportions of gases in our atmosphere stablise?

Answer 16

200 million

Question 17

What gases make up our atmosphere today and in what proportions?

Answer 17

• Nitrogen 78%
• Oxygen 21%
• CO₂, Argon, water vapour, other nobel gases, and other gases 1%

Question 18

How can the gases in the air be separated?

Answer 18

• Gases in the air have different boiling points, so can be separated from liquid air by fractional distillation
• This is done industrially to produce pure oxygen and liquid nitrogen
• The air is cooled to below -200°C and fed into a fractional distillation column
• Nitrogen is first separated from oxygen + argon.
• Further distillation is used to produce pure oxygen and argon

Question 19

Why has the amount of carbon dioxide in the atmosphere remained stable for about 200 million years?

Answer 19

Because various natural processes that move carbon dioxide into and out of the atmosphere have achieved a balance

Question 20

What processes move carbon in and out of the atmosphere?

Answer 20

Processes involving:

• Plants
• Animals
• The oceans
• Rocks

The organic carbon cycle shows some of these processes

Question 21

Carbon dioxide dissolves in…

Answer 21

…water, particularly the oceans

Question 22

The reactions of what are important in maintaining the balance of carbon dioxide in the atmosphere?

Answer 22

The reactions of inorganic carbon compounds

Question 23

Why has the amount of carbon dioxide in the atmosphere increased recently?

Answer 23

Due to human activity, specifically the large amounts of fossil fuels we burn

Question 24

Draw a diagram of the organic carbon cycle

Answer 24