What is the best explanation for why Earth's lithospheric plates move?
The best explanation for why Earth's lithospheric plates move is attributed to the process known as plate tectonics. Plate tectonics is driven by the convective movements within Earth's mantle, known as mantle convection. The interior of the Earth contains a hot, semi-fluid layer called the asthenosphere, which lies just below the lithosphere. This asthenosphere undergoes convective movements due to the intense heat from the Earth's core.
The convection currents within the asthenosphere cause the lithospheric plates to move. As the hotter, less dense material rises, it exerts a force on the overlying lithosphere, causing it to move away. This process is known as ridge push. At the same time, cooler, denser material from the lithosphere sinks into the asthenosphere, creating a downward force that drags the plates with it. This process is called slab pull.
The combined forces of ridge push and slab pull create tension and compression in the lithosphere, causing the plates to move. When plates collide, they form convergent boundaries where one plate is forced beneath the other (subduction). At divergent boundaries, plates move apart from each other, creating new crust as magma rises to the surface.
Overall, the movement of Earth's lithospheric plates is a result of the convective motions occurring within the underlying asthenosphere, leading to the continuous process of plate tectonics.