EVOLUCIóN GEOMORFOLóGICA DEL VALLE DE ABURRá Y SUS IMPLICACIONES EN LA OCURRENCIA DE MOVIMIENTOS EN MASA

the ancient and recent history of the aburrávalley has been characterized by the occurrence of numerous landslides. those have has caused great economic losses and casualties. in this study, a survey was carried out in the aburrávalley to examine the link between landscape evolution and landslide occurrence. the objective of this investigation was to unravel the dynamic and mechanism of the valley slopes for understanding contemporary landslide occurrence. topographic analyses, geomorphological mapping, slope deposit geochronology (14c, fission track), terrace correlation, and stream longitudinal profiles were carried out. the iguanástream is a broad knickzone composed of many separate knickpoints which a common downstream origin, the medellín river. terrace surfaces diverge in the downstream direction and project directly to knickpoints that are propagating upstream. long-term evolution of the iguanástream is controlled by the mechanism of knickpoint upstream migration. evolution of the aburrávalley during the last millions years has been determined on the basis of this mechanism and the geomorphological classification of the aburrávalley slopes;tectonic episodes may have lowered the base level of the medellín river, forming knickpoints. these knickpoints migrate upstream through the medellín river tributaries as pulses of dissection, eating back into the higher and older sections. stream incision initiates upward slope overstepping, changing morphogenetic regime from general slope stability to potential instability. finally, mass movements are generated to reestablish gentler surfaces, forming a new staircase level in a lower position.