PHENOMENES GEOGRAPHIQUES DE RISQUE DANS LA DEPRESSION DE LA TRANSYLVANIE
ABSTRACT. – Geographical Risk Phenomena in the Transylvanian Basin. The Transylvanian Basin is the largest basin area (approximately 26.000 km2) of Romania. It had, up to the Late Cretacic, a similar evolution to the Carpathians which surround it like a “ring”. Sunk during the Laramian – Alpine movements and flooded by the sea, the basin became a large sedimentary area where the thickness of the Miocene-Pliocene deposits has maximum values. Its present morphology represented by domes and diapiric folds, of average heights that very between 400 and 500 metres, is the sculptural result of a hydrological network that has mostly a Carpathian origin, and which has been favoured by hightly consolidated rocks belonging to the Badenian and the Sarmatian periods. The geological structure as well as the palaco- climates characterising the Romanian territory at different periods, has led to a magnifying of the highly large land slides know as “glimee”. Caused by the sometimes very abundant and periodical rainfall of the Transylvanian Basin, these processes are always accompanied by floods. Although largely stabilized at present, these processes are periodically reactivated and thus they cause significant damage to the agricultural area as well as to the inhabited area (both the rural and the urban ones). An instance of these damaging effects is the land slide maximum recrudencence periods of 1912-1913, 1941-1942 and 1970-1972. The violence of these landslides, which sometimes have a daily average speed of over 1 metre, caused significant material damage and no human life loss. The loss, caused by floods and landslides in the Transylvanian Basin during 1970-1972, was estimated to several million dollars. In the context of risk analysis, we insist on the tight interdependence of the risk causing phenomena within the Transylvanian Basin. Several prevention methods as well as a geographical risk phenomena prognosis are also offered.