Structure of the Earth
- The Earth is almost spherical with a radius of about 6400km. At the surface is a thin, soild crust. The thickness of the crust varies between 5 km and 70 km. It is the thinnest under the sea.
- The mantle is under the crust. It is about 3000 km thick and so goes almost halfway to the centre of the Earth. The mantle is almost entirely soild, but it can very slowly.
- The core is very dense amd made of metals, mainly nickel and iron. The outer core is liquid and the inner core is solid. This model of the Earth was built up using evidence from seismic waves from earthquakes.
Scientists once thought that mountains and valleys where formed by the Earth shrinking. They believed that the crust solidifed as the Earth cooled down then the Earth continued to shrink, causing the crust to wrinkle.
REMEMBER: the inner core is solid and the outer core is liquid.