Changes in the Earth and its Atmosphere

Question 1

What is the structure of the Earth?

Answer 1

The crust is the thinnest. The mantle is the thickest.

Question 2

What is the ‘baked apple’ theory?

Answer 2

Early Earth, hot and covered in magma. This cools and the Earcths crust forms. It continues to shrink and the earths crust wrinkles.

This theory is NOT accepted because there is no evidence to support it.

Question 3

What is continental Drift? Is it accepted, if so why?

Answer 3

Alfred Wegener came up with this theory. It says that once, all of the countries were joinined together and over millions of years and they drifted apart. He named the super continent Pangaea.

It is accepted because there is lots of evidence for continental drift.

• There is a jigsaw fit of the continents
• There were similar rocks found in South America and Africa
• Identical fossils of land animals that couldn’t swim found in both South Africa and Africa

Question 4

What causes the continents to move?

Answer 4

Convection currents in the mantle are responcible for the moving continents. Radioactive processes in the core produce heat. This heat causes convection currents in the mantle

Question 5

Describe in detail how the Earth’s atmosphere evolved.

Answer 5

The Earth’s crust and the upper part of the mantle are separated into sections called Tectonic plates. Earthquakes and volcanos occur at the edges of Tectonic plates.There were lots of volcanos that produced carbon dioxide and a small amount of water vapour and nitrogen. The Earth’s early atmosphere was mainly carbon dioxide. The water vapour condenced to form oceans. Simple life began to form in the oceans and photosynthesis occured which reduced the amount of CO₂in the atmosphere.

Question 6

Where did all of the CO₂ go?

Answer 6

• Earth’s early atmosphere- 96% CO₂
• Earth’s current atmosphere- 0.04% CO₂​

The CO₂ has reduced because it has been ‘locked up’ in sedimentary rocks (limestone). Plants absorb carbon dioxide for photosynthesis. CO₂dissolves in the oceans. Salt water can absorb more carbon dioxide than still water without becoming acidic.

Question 7

What happened to the Ammonia and Methane?

Answer 7

These gasses are no longer in the atmosphere because they have reacted with increasing levels of oxygen.

CH₄ + 2O₂—> CO₂ + 2H₂0

4NH₃ + 30₂ —> 2N₂ + 6H₂0