The heat generated from the planet formation process, the radioactive decay of certain elements, and friction between the layers have kept the Earth’s core at extremely high temperatures after 4.5 billion years.
At the center of the Earth, temperatures reach up to 5,200 degrees Celsius, nearly as hot as the surface of the Sun. This hellish temperature is sustained by forces that have existed for billions of years, according to IFL Science. The Earth’s core is divided into two distinct regions: the outer core, primarily composed of molten iron and nickel, and the inner core, essentially a large solid sphere about the size of the Moon, made up of two metals.
Simulation of the Earth’s core. (Photo: Physic World).
Despite the extreme temperatures within the core, we cannot feel this heat on the surface except through volcanic activity and geothermal springs. The outer core begins at a depth of 2,889 km beneath the Earth’s crust. Between the crust and the outer core lies a significant amount of material, where the mantle contains rock that absorbs and disperses heat. In fact, there is no way to directly measure the heat. Since it is impossible to send probes or people deep into the Earth’s interior, scientists calculate temperature by studying how iron and iron-rich compounds melt under high pressure. By determining the melting temperature, they can infer the temperature in the core.
Some of this heat is a remnant from the past, linked to the planet’s formation. The Earth would cool quickly, while the core remains the last area to cool down. The Earth formed about 4.5 billion years ago when gravity condensed a mass of material from a cloud of hot gas and particles surrounding the young Sun. As the molten sphere cooled, the outer layer solidified like candle wax, forming the crust. However, the mantle still retains some heat and continues to cool gradually.
A study in 2011 estimated that the residual heat from the planet formation process accounts for nearly half of the heat within the Earth. The remaining heat comes from the radioactive decay of uranium-238 and thorium-232 in the planet’s core, comprising about 54%. Lastly, heat is also generated from the friction caused by the movement of solid and liquid layers under immense pressure.
The heat within the Earth is crucial for the surface because it is the primary driver behind tectonic plates, causing them to move around, creating or destroying continents. Researchers predict that the Earth’s core will cool and solidify 91 billion years after the Sun dies.
