what is the best explanation for why earth's lithospheric plates move
The movement of Earth's lithospheric plates is best explained by plate tectonics theory. According to this theory, the lithosphere is divided into several rigid plates that float on the semi-fluid asthenosphere beneath them. The movement of these plates is driven by convection currents in the underlying asthenosphere.
Heat from Earth's interior causes the asthenosphere to become partially molten and convective currents are established due to the density differences of the material. Convection currents circulate within the asthenosphere, carrying heat towards the surface. As the heated material rises, it pulls apart the plate above, creating a divergent boundary. At divergent boundaries, new crust is formed as magma rises and solidifies, pushing the adjacent plates apart.
On the other hand, at convergent boundaries, two plates collide with each other, leading to different types of interactions depending on their composition and density. When an oceanic plate collides with a less dense continental plate, the continental plate overrides the oceanic plate, causing subduction. The sinking oceanic plate is forced down into the mantle, leading to the formation of volcanic arcs and trenches.
When two oceanic plates collide, the denser plate is subducted beneath the other, accompanied by the formation of volcanic island arcs. Similarly, when two continental plates collide, neither plate can subduct due to their low density. Instead, the plates crumple and create mountain ranges, such as the Himalayas.
Transform boundaries occur when two plates slide past each other horizontally. This movement creates faults where the plates slip, causing earthquakes. The most well-known example is the San Andreas Fault in California.
In summary, plate tectonics theory explains that the movement of Earth's lithospheric plates is primarily driven by convection currents in the underlying asthenosphere due to heat from the Earth's interior. This movement gives rise to various types of plate boundaries and geological features across the planet.