What are the theories about the changes in the lithosphere?

Some theories about changes in the lithosphere include plate tectonics, which explains how the Earth's outer shell is divided into plates that move and interact with each other, leading to processes like earthquakes and mountain formation. Another theory is mantle convection, where heat from the Earth's core causes movement in the mantle, influencing the behavior of the lithosphere above. Additionally, the theory of isostasy describes how the lithosphere floats on the denser asthenosphere, adjusting its elevation to maintain equilibrium with the underlying mantle.