In this chapter, we address the issue of long-term erosion processes and resulting erosional landformsErosional landforms (in general) particularly in terrestrial environments. As discussed in the previous chapter, the predominance of rapid erosion processes on an active volcano, mainly in the proximal and medial areas, is due, in addition to endogenous factors (e.g. seismicity), to the steep slopes, instability, and erodibility of the accumulated volcanic pile. Lahars and flood flows, which typically move further down the drainage system, commonly affect the distal areas, too.