Tectonic plate: A large slab of the earth’s crust. Plates are irregular in shape and made of solid rock.
Plate boundary: Where plates meet.
Crust: The thin outer layer of the earth, made up of solid rock. The crust is between 30 and 70 km thick on continents and 5 and 11 km thick under the oceans.
Mantle: Found underneath the crust. Consists of hot molten (melted) and semi-molten rock known as magma . The mantle moves around in the form of very slow currents. Temperatures can reach 4,000 Celsius (°C) here.
Outer core: Consists of liquid nickel and iron – this is molten.
Inner core: The solid centre of the earth. Temperatures here are extremely high – up to 6,000 °C.
3. The structure of the earth The Earth’s Crust
The earth is made up of several different layers. The outer layer is known as the crust and is made of solid rock. The crust ranges from 5 to 70 km in depth and is split into a number of pieces known as plates. Some plates have oceans on top and are known as oceanic crust. This is dense, thinner and mainly made of basalt rock. Other plates have land on top of them. This is known as continental crust and it is less dense, thicker and mainly made up of granite. The point where plates meet is called a plate boundary.
FUN FACT! Below Central Valley in
California, US, the crust is only
20 km thick, but under the Himalayas it has a thickness of up to 70 km. Underneath the ocean, it has a thickness of 5–11 km.