Four radioactive isotopes inside Earth account for about 50% of Earth’s internal heat.
Like a slow cooker, they constantly release heat within the planet keeping it on a light simmer.
These four isotopes are uranium-238 (238U), uranium-235 (235U), thorium-232 (232Th) and potassium-40 (40K).
The majority of the heat transfer occur at mid-oceanic ridges. Whereas the least amount of heat transfer is from the continental interiors.
A source of energy for plate tectonics
Certain isotopes of elements are unstable and radioactive. For example, uranium, thorium and potassium isotopes are deep within the interior of Earth.
These radioactive isotopes generate 50% of Earth’s radiogenic heat from radioactive decay. The remaining 50% of Earth’s internal heat budget is from primordial heat after its initial formation.
It’s from this radioactive heat in the mantle that makes our planet geologically active. The majority of internal heat transfer occur volcanically at mid-oceanic ridges. This process drives mantle convection and plate tectonic motion on the planet.
These radioactive isotopes have long lifetimes before they decay and release slow amounts of energy. It’s because of these 4 isotopes that Earth maintains a cozy temperature in the mantle.
Radioactive decay heat in the asthenosphere
Now that we have a heat source inside Earth, it’s the asthenosphere where the convection cycle occurs because particles can freely flow.
But in our rigid lithosphere which is a solid, particles cannot freely move.
As heat rises, it starts a mantle convection cycle. It tears apart the Earth to form mid-oceanic ridges (tensional force). When it sinks down, it breaks it apart (compressional force).
Slab pull is the main mechanism pulling the lithosphere apart at divergent plate boundaries.
Slab pull and plate tectonics
Because of the convection cycles that occur deep inside Earth, it’s the force that breaks apart the whole lithosphere into 7 major plate tectonics and 12 or so minor ones.
At divergent plates boundaries, plates pull apart from each other. In turn, lava spews out to create the youngest geological rocks on Earth.
At the opposite end, convergent plate boundaries smash into each other like a demolition derby. The force is so incredible that it causes volcanoes, earthquakes and mountain building events.
We leverage radioactive decay in nuclear power plants
We use uranium and thorium in nuclear power plants in order to make fuel for fission reactors. Because of the possibility of overheating, nuclear power plants are usually located close to a source of water to cool down.
Certain elements have isotopes with a specific number of neutrons such as uranium-238 (238U). Each number corresponds to the number of protons and neutrons in its nucleus.
Overall, it’s the weak nuclear force that is responsible mostly for decay. For example, this force can change an electron into a neutrino, and a neutron into a proton. Through this force, atoms will decay or end up unstable and radioactive.