Part of the show Cambridge Science Festival - Virtual Anatomy
How far down is it to the centre of the Earth ?
The radius of the Earth, or in other words the distance to the centre, is 6,300 km or 3,963 miles. That means the Earth is 12,600km (7,926 miles in diameter) wide in total. The earth has 4 main parts, the crust, mantle and the inner and outer cores. The core is the biggest bit and is 3500 km or 2100 miles wide. It is between 4,300 and 7,200 degrees celsius in the middle of the earth which is hotter than the sun's surface. The inner core is solid iron and the outer core is liquid iron and sulphur. The mantle is between 100 to 250 km deep, and is 3700°C. It contains solid magnesium, iron, aluminium, silicon, and oxygen silicate compounds, which can move about in a plastic like way. The crust or top layer of the earth is the smallest part and is 6 to 11 km under the oceans, and 25 to 90 km thick under the land. This part contains calcium and sodium aluminium silicate minerals. The World's deepest hole is 40,000 feet deep (that's about 7.5 miles). It's in Russia, on the Kola Peninsula near the Norwegian border. They have been drilling since 1970, to gain a better understanding of the Earth's crust which is on average 20 miles thick. The previous deepest hole was in Oklahoma in the USA where a gas well stopped at 32,000 feet (6 miles deep).