In previous chapters we have learned about how landforms are created. Mountains, and valleys form as tectonic plates crash into one another. These mountains do not last forever. As they age, they are torn down by the very slow, but persistent forces of weathering, mass wasting, and erosion.In this chapter we will examine the first two processes, which are weathering, and mass wasting. These two forces are usually overlooked when people consider the development of landscape, yet they are incredibly important.