National Geographic reports that the temperature of the Earth’s outer core is estimated to be between 7,200 and 9,000 degrees Fahrenheit. Due to this high temperature, the outer core is liquid despite being made up of iron and nickel.
The high temperature of the outer core is the result of decaying radioactive elements and frictional heating from denser materials sinking to the center of the earth. Moreover, the Earth still retains some of the heat from when it was formed. To determine the temperature of the outer core, scientists first estimate the density and thickness of the Earth’s layers by capturing and analyzing seismic waves from earthquakes. They then use computer models and laboratory experiments to infer the temperature.