Restless Planet

2. Masses of water formed when water vapour in the Earth's atmosphere cooled and condensed.
5. The layer below the Earth's crust which can flow despite the fact that it is solid.
7. Gas which is most abundant in the Earth's atmosphere today.
8. The first life forms on Earth.
9. Gas which was most abundant in the early atmosphere of the Earth.
10. Type of currents in the mantle which cause the tectonic plates to move.
12. Miller-Urey's theory to explain the formation of life on Earth.
13. Nitrogen containing gas found in the early atmosphere of the Earth.

1. Outer layer of the Earth which is broken into tectonic plates.
3. Violent tremors which can occur where plates collide or move past each other.
4. Process carried out by plants and algae which releases Oxygen into the atmosphere.
6. Process taking place in all living organisms which releases Carbon dioxide gas.
10. area at the centre of the Earth which contains magnetic metals such as iron, nickel & cobalt.
11. A feature which can occur at plate boundaries where two plates meet.