Earth and changing atmosphere

Question 1

Crust

Answer 1

Outer layer of the earth – between 5-70km thick

Question 2

Mantle

Answer 2

The layer under the crust – about 3000km thick. Behaves like a solid but can flow slowly - convection currents.

Question 3

Core

Answer 3

The central part of the earth. Made of the magnetic metals nickel and iron. The outer core is liquid and the inner core is solid.

Question 4

Convection currents

Answer 4

Radioactive decay within the earth produces energy. This heats up the mantle, which becomes less dense and rises upwards towards the crust.

Question 5

Tectonic plates

Answer 5

The crust is cracked into huge sections called plates.

Question 6

Earthquakes

Answer 6

Sudden movement caused by plates sliding past each other.

Found at plate boundaries.

Question 7

Volcanoes

Answer 7

Caused when two plates collide and molten rock comes to the surface.

Found at plate boundaries.

Question 8

Early atmosphere

Answer 8

4 billion years ago the earth’s atmosphere was mostly carbon dioxide, with some methane and ammonia.

Atmosphere made by intense volcanic atmosphere.

Water vapour formed the oceans.

Question 9

Modern Atmosphere

Explain changes from early earth

Answer 9

Consists of 79% nitrogen, 20% oxygen, and small amounts of carbon dioxide, water and noble gases.

Changes from earlier atmosphere

Increase in oxygen due to photosynthesis in plants and algae.

Decrease in carbon dioxide due to absorption in photosynthesis, ocean and locked up in fossil fuels and sedimentary rocks.

Question 10

Describe the Miller-Urey experiment

Answer 10

An experiment to support the theory of how life was formed.

Involves a mixture known as ‘primordial soup’ which contained hydrocarbons (methane) and ammonia and electrical sparks that pretended to be lightening.

Results formed basic blocks of life – amino acids.