In the previous two chapters, we have examined how different internal processes modify and transform the surface of planet Earth. Now, we will turn our focus to the various external processes that also influence the geography of our planet.

Exogenous processes are fuelled by the energy that is radiates to planet Earth from the Sun. Exogenous processes transform landscapes of our planet by wearing down its surface, transporting loose substances, and by piling up these materials in different places. The result of exogenous processes is the wearing down of Earth's surface. This phenomenon is known as erosion. The most significant sources of erosion are flowing water, ice, waves and the wind. In this chapter, we will examine the ways in which these processes transform the surface of the Earth.

Solid rock can also wear down and break. This process is called weathering. It will be discussed in the following chapter.