The lithosphere is the solid rocky crust of the Earth, composed of minerals and divided into tectonic plates that move over the mantle. Internal forces like earthquakes and volcanoes, along with external agents such as water and wind, shape the Earth's relief, which includes various landforms like mountains, valleys, and plains. Over millions of years, the continents were once united as Pangea and have changed due to the movement of tectonic plates and other geological processes.