Earth's Structure
- The Earth has four main layers:
- The crust
- The mantle
- The outer core
- The inner core
Crust
- There are two types of crust:
- Continental - a thicker (up to 70km), less dense layer mainly composed of granite
- Oceanic - a thinner (5-10km) , denser layer mainly composed of basalt
Mantle
- The mantle is between the crust and core and is the widest layer (2900km)
- The upper mantle has two layers
- The rigid layer above the asthenosphere which together with the crust makes up the lithosphere
- The asthenosphere is a plastic-type layer which moves very slowly under high pressure and carries the lithosphere on top
- The lower mantle is hotter and denser than the upper mantle
- The intense pressure, at depth, keeps the lower mantle solid
Core
- The core is made up of two parts:
- Inner Core - solid centre, mostly composed of iron
- Outer core - semi-molten, mostly liquid iron and nickel
Earth's structure
- The lithosphere consists of seven major and several minor tectonic plates which float on top of the asthenosphere
Tectonic plates
- The core is the hottest part of the Earth, and this heat is the main driver of tectonic activity
- There are two key causes of this extreme heat:
- Radioactive decay of elements such as uranium and potassium inside the earth’s core
- Heat left over from the collisions of asteroids and other small bodies which resulted in the formation of Earth
