Why is the center of the earth hot?

The earth, like all of the planets in our solar system, had a very violent start in its creation. There are areas in space that are called the ‘planetary nurseries’ and they are filled with gas, dust and various elements. When the pressure builds up inside of them, combined with a potential ‘trigger’ (like an old star that explodes), it causes the creation of a star and all of the contents explode outward. There is an incredible amount of energy that is released in the beginning stages of the creation of stars and planets. Part of this energy is why the center of the earth is hot.

Structure of the Earth

Not all planets have a center or core that is hot. It is believed that when earth was created, over billions of years, there were actually large chunks of asteroids and planetary objects hitting each other from the explosion. As each one crashed into another, energy was produced, making the center hotter and hotter. Each ‘hit’ also made the almost-planet spin in rotation. The more hits it got, the higher the energy level and the heat moved further towards the center.

The bigger the planet got, the more it developed internal energy. The spinning, or rotation, also allowed the development of gravity and the hot molten metals that were contained in the asteroids allowed the slow development of a magnetic field as they circled around with the rotation. As more objects hit and were absorbed, the heat went deeper and deeper into the center of the developing earth.

The temperatures and chemical reactions that began to happen became so intense that it began to cause radioactivity, which actually made the center of the earth like a ‘heat engine’. This means that the center of the earth kept regenerating heat so that it replaced any that might have escaped in any cooling process.

Schematic view of the interior of Earth.

You might find it funny to know that we are called ‘crust dwellers’. That’s because we live and exist along with all of the other animals and plants, on the ‘crust’ of the earth. Deep below the earth is the core and there are many layers between the hot core and the crust. The core itself is about the size of a dwarf planet, like Pluto. It is in 2 parts, with the inner most core about the size of our moon and is thought to have the same density as steel. The next section of the core is the layer of hot molten metal. Beyond that is the mantle, which is hot molten rock. Most of the earth’s heat is contained in the mantle.

The outer cooled surface is the ‘crust’, where we live. When pressure builds up in the mantle, cracks appear and go all the way to the surface. More pressure from the heat can push the surface up and the molten rock from the mantle has to go somewhere, so that is when we have volcanic eruptions. Although we think we are walking on firm ground, the outer crust is actually floating on the mantle and is moving. The movement is very slow so we don’t notice any changes, unless the pressure builds up and parts of the crust move to cause an earthquake.

The heat from the center of the earth is the reason the planet is constantly changing. The hot core was created when our planet was first born and it continues to generate heat.

Why is it so hot inside Earth’s core?

What heats the earth’s core?