Week 5 - Earth, Moon and Atmosphere

Question 1

Outline the major stages in the formation of the Earth.

Answer 1

1. Accretion
2. Differentiation
3. The Big Splat (or the Giant Impact Hypothesis)
4. Stabilisation

Question 2

Describe how the atmosphere formed.

Answer 2

Around 4.6 GYA ago volcanoes began to spit out molten rock & gases (outgassing). H & He escaped Earths gravity while heavier elements were retained as gaseous layer or atmosphere.

Question 3

Describe how the oceans formed.

Answer 3

Eruptions also led to the outgassing of water from Earths interior. Water vapour condensed in cooler parts of the atmosphere. Surface water then collected and flowed to the lowest parts of Earths surface to form oceans.

Question 4

Explain why the composition of the atmosphere changed over time.

Answer 4

Earths original atmosphere was 12% CO2, now only 0.04% is CO2.

Reason:

1. Cyanobacteria - photosynthesis convert CO2 + sunlight to sugars, water and oxygen.
2. Tied up in carbonate rocks e.g. limestone
3. Trapped in rock layers - hydrocarbons (coal, oil, gas)

Question 5

Briefly describe the atmospheres of the terrestrial planets

Answer 5

Mercury - traces of sodium
Venus - 96% CO2 and 4% N
Earth - 78% N, 21% O
Mars - 95% CO2

Question 6

Briefly describe the atmospheres of the Jovian planets

Answer 6

Jupiter - 86% H, 14% He
Saturn - 92% H, 7.4% He
Uranus - 84% H, 14% He
Neptune - 84% H, ? He

Question 7

How did the Moon form?

Answer 7

Glancing collision with a Mars sized body.

Question 8

How did/does the Moon affect life on Earth?

Answer 8

Tides - 2/3 Moon, 1/3 from Sun

Stabilises Earths rotation axis - if not present, obliquity could vary wildly (this happened on Mars)

Seasons would also fluctuate erratically