What is the Earth's core made of?
Earth's core is made mostly of iron and nickel. It has a liquid outer core and a solid inner core, which is about as hot as the surface of the Sun.
The core begins about 2,900 kilometers below the surface. The outer core is a layer of molten iron and nickel about 2,200 kilometers thick. The inner core is a solid ball about 1,220 kilometers in radius. It stays solid despite temperatures of around 5,000 to 6,000 degrees Celsius because of the enormous pressure.
No one has ever drilled anywhere near the core. The deepest hole, the Kola Superdeep Borehole in Russia, reached only about 12 kilometers. Scientists learn about the core by studying how seismic waves from earthquakes travel through the planet, bending and changing speed in different layers.
Earth's magnetic shield
The swirling liquid iron in the outer core creates Earth's magnetic field, a process called the geodynamo. This field protects the planet from harmful charged particles from the Sun and causes the auroras near the poles. It also lets compasses work.
Did You Know?
Studies suggest the inner core's rotation speed changes slightly over decades compared with the rest of the planet, a topic scientists are still debating.