The primary sources of heat that drive mantle convection currents are: (1) internal heating from the radioactive decay of elements like uranium, thorium, and potassium; (2) the Earth's long-term secular cooling (residual heat from the planet's formation); and (3) heat transfer from the Earth's core.
Here's a breakdown of each heat source:
-
Radioactive Decay: The decay of radioactive isotopes of uranium, thorium, and potassium within the mantle generates a significant amount of heat. This is a continuous process, constantly supplying thermal energy to the mantle.
-
Secular Cooling: The Earth is slowly cooling down from its initial formation billions of years ago. This residual heat contributes to the overall thermal budget of the mantle, although its contribution is decreasing over time compared to radioactive decay.
-
Core Heat: Heat from the Earth's core, which is extremely hot due to its formation and ongoing processes, flows into the mantle. This heat transfer plays a role in driving convection, especially in the lower mantle.
These heat sources create temperature differences within the mantle. Hotter, less dense material rises, while cooler, denser material sinks. This continuous cycle of rising and sinking material is what we call mantle convection, and it is responsible for plate tectonics and many other geological phenomena.
