The flow of the Earth’s mantle is primarily caused by the heat generated from the Earth’s core, combined with the pressure and the unique properties of mantle materials. This heat causes the rock in the mantle to become less viscous, allowing it to flow over geological timescales.
In detail, the Earth’s core is extremely hot, with temperatures reaching up to 5,000 degrees Celsius (about 9,000 degrees Fahrenheit). This intense heat radiates outward, heating the lower mantle and causing convection currents. As the lower mantle material heats up, it becomes less dense and rises toward the surface. Once it reaches the upper mantle, it cools down, becomes denser, and then sinks back down. This cycle of rising and sinking creates a convective flow.
Moreover, the mantle is not entirely solid; it behaves like a viscous fluid over long periods. This is due to the minerals present in the mantle and the immense pressures at depths that allow for some deformation. The combination of thermal energy and the properties of mantle rocks create a dynamic system that is crucial for plate tectonics, volcanic activity, and the overall geology of our planet.