Scientists believe that the movement of Earth's lithospheric plates is driven by several processes related to the dynamics of the Earth's interior. Here are the main processes thought to be responsible for plate tectonics:
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Mantle Convection: The Earth's mantle is a semi-solid layer that is capable of flow over long timescales. Heat from the Earth's core causes convection currents in the mantle. Hotter, less dense material rises, while cooler, denser material sinks. These convection currents create drag on the base of the lithosphere, leading to the movement of tectonic plates.
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Slab Pull: When tectonic plates converge, one plate may be forced beneath another in a process called subduction. The descending plate, or slab, pulls the rest of the plate down with it because of its density. This can drive further motion of adjacent plates.
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Ridge Push: At mid-ocean ridges, new oceanic crust is created as magma rises to the surface. This new crust is elevated compared to the older, cooler crust farther away from the ridge. The gravitational force acting on the elevated ridge causes the older lithosphere to slide away from the ridge, contributing to plate movement.
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Plate Interaction: The plates interact at their boundaries in various ways (divergent, convergent, and transform boundaries). These interactions can create stresses and lead to the movement of plates. For example, as continents collide, they can push against each other, causing uplift and deformation.
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Thermal Expansion and Contraction: The thermal changes in the mantle can also contribute to the movement of tectonic plates through expansion and contraction, influencing the forces at plate boundaries.
Together, these processes create a dynamic system that drives the movement of the Earth's lithosphere plates, resulting in geological activity such as earthquakes, volcanic eruptions, and the formation of mountain ranges.