Geomorphologische und hygrische Höhenzonierung des Andenwestabfalls im peruanisch-chilenischen Grenzgebiet

Abstract

In the hinterland of Arica (northernmost Chile) the slopes are dissected by many gullies at levels of medium elevation, whereas they are conspicuously plane both further down and further up. The intensive linear erosion at the level of the gullies is mainly caused by rare but strong rainfall on bare ground. From this level dissection decreases both downward because rainfall becomes extremely scarce and upward because the vegetation spreads more densely under the influence of regular rainfall. This decreasing tendency of dissection is one of the main conditions under which plane slopes develop. Moreover their formation depends on the production of scree by mechanical weathering on the whole surface of the slope and its moving downhill under the influence of gravity. In the periglacial region the scree is produced by frequent freeze-thaw cycles, whereas at the level of the coastal fogs it is the result of the alternating process of moistening and dessication, which causes crystal growth or hydration of salt. In spite of these different processes at work, the morphological results are the plane slopes both in the periglacial region and at the level of the coastal fogs. Moreover there are other similarities between these two levels, namely the smooth forms, stone stripes, and earth arcs or terracettes.