The movement of Earth's tectonic plates is primarily driven by the heat from the Earth's interior, which causes convection currents in the semi-fluid asthenosphere beneath the rigid lithosphere. These convection currents are the result of:
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Heat from radioactive decay: The decay of radioactive isotopes within the Earth's mantle generates heat, contributing to the convection process.
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Residual heat from Earth's formation: When the Earth formed about 4.5 billion years ago, a significant amount of heat was produced from accretion and other early processes, and some of this heat still persists.
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Gravitational forces: These forces can contribute to plate movements through processes like slab pull (when a dense oceanic plate sinks into the mantle at a subduction zone) and ridge push (when the elevation of mid-ocean ridges causes plates to slide away from the ridge).
These processes work together to create the dynamic environment that leads to the movement of tectonic plates, which can result in geological phenomena such as earthquakes, volcanic activity, and the formation of mountain ranges.