Well the topmost layer of the earth (aside from the atmospher) would be the crust. It is made up of tectonic plates that move in different directions. The collisons and abrasions made by these plates sliding and crashing into each other means that mountain ranges pop up like wrinkles, and continents can move around over time. This happens over millions of years.
The main source of heat of the earth that keeps plasticity the mantle is earth’s radioactive core. The part of the mantle close to the core is hotter than that closer to the crust. Therefore, the mantle has convectional currents. These currents drag with them the earth crust above and hence tectonic plate movements. At convergent boundaries, the earth's crust is pressed onto one another to form fold mountains such as the Himalayas. At divergent boundaries, faulting occurs and the subsequent crust depression is filled with water to form oceans.
