Here’s our top ten facts on Earth Structure and Composition:

1. We can’t see the layers that the Earth is made up of but scientists have used data from the seismic waves produced during earthquakes to predict their properties.
2. The inner core of the Earth is mainly iron at a temperature of around 5 000 °C. The enormous pressure acting on the core keeps the iron solid (at normal pressure it would have melted at 1 500°C).
3. Scientists think that the Earth’s magnetic field is generated by the core. Sometime within the next few thousand years they think that the field could flip, with the magnetic north pole becoming the south and vice versa.
4. The deepest hole ever dug is in Russia and is called the Kola Superdeep Borehole. It is 12 km deep but only reaches a third of the way through the crust.
5. Molten rock under the Earth’s surface is called magma. When it reaches above the Earth’s surface it is called lava.
6. When magma rises to the surface of the Earth and cools it forms extrusive igneous rocks such as basalt. Because of the quick speed of cooling, they have small crystals.
7. When lava cools under the surface of the Earth it forms intrusive igneous rock which has large crystals because of the slow cooling. An example is granite.
8. 95% of the Earth’s crust is made of igneous rock.
9. Metamorphic rocks are so called because they start off as another type of rock. You will have heard of metamorphosis as a stage in some animals’ life cycle when they change from one form into another.
10. Sedimentary rocks form in layers, the oldest being at the bottom. Fossils can be found in the layers and this gives us clues about the age of the surrounding rock.