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A morphometric analysis that considers hypsometry and topographic slope reveals longitudinal and latitudinal differences in the degree of maturity of the relief of the Andes between 27-32 degrees S. Whereas landscape rejuvenation of the Coastal Cordillera takes place to the south of 29.5 degrees S, in the Main Cordillera it happens south of 28.5 degrees S. The combination of a wetter climate towards the south and the presence of segments with different tectonic features would explain these variations. Longitudinally, the geomorphological features indicate the presence of a mountain front that separates the Coastal Cordillera and the Main Cordillera. Between 28.5 and 30.5 degrees S this front can be attributed to the activity of the Vicuna-San Felix Fault System, wich during the Oligocene-Early Miocene would have accommodated the relative uplift of the Main Cordillera. In response to this tectonic activity, successive levels of cut-and-fill pediments may have been formed. During the Middle Miocene, there was a new episode of uplift affecting the fore-arc and it is in response to this uplift that the valleys that cross this region were excavated. Between 28.5 and 30.5 degrees S, the valleys head reached a sufficient altitude to generate fluvio-glacial erosion that allowed the incision of deep canyons in this segment of the Main Cordillera.