Over the last few years a revision of the geological mapping of Madeira Island has been undertaken. The island rises above a vast underwater submarine plain in the midst of the African Plate, forming a volcanic massif about 5,5km high, of which only a third is above sea level. Its irregular topography is mainly due to lithologic, tectonic, structural and inherited geomorphological factors. Seven main stratigraphic units were differentiated: Ancient Volcanic Complex (CA); Lameiros marine limestones (CM); Conglomerate Breccia unit (CB); Main Volcanic Complex (CP); S. Roque-Paul Volcanic Complex (SRP); Younger Volcanics (VR) and recent sedimentary deposits. Besides the recent slope deposits, the ancient volcanic complex is the unit where more slope movements were recorded, such as in S. Vicente valley and Caniçal, among other places. A correlation is made between the volcanostratigraphic units and the different types of slope movements most frequent in Madeira Island.
Madeira is located in the eastern region of the Atlantic Ocean, between longitudes 16°39″- A7°16″W and latitudes 32°38″-32°52″N. The island rises from a vast submarine plain in the African Plate, forming a 5.5km high volcanic massif, of which only a third is above sea level. Madeira's volcanic activity started before late Miocene (the oldest known age is 5.2 Ma; Mata 1996; Prada & Serralheiro 2000) and continued into the Holocene with the youngest dated eruption Occurring 6,000–7,000 years BP (Geldmacher et al. 2000). The island grew through the accumulation of explosive and effusive volcanic materials. The outcropping lavas at Madeira Island can be considered as members of an alcaline suite with composition extending to traquites, but with a neat predominance of mafic terms (basanite and alcaline basalts) (Mata 1996). Precipitation increases with altitude, being higher on the northern slopes than in the southern slopes for the same altitude. The highest rates of precipitation are at Bica da Cana, at an altitude of 1560m, with a maximum rate of 2966.5 mm/year, which decreases above this altitude. In terms of the general morphology, the island is formed by two main blocks, separated by the deeply incised valleys of S. Vicente and Ribeira Brava. The eastern zone is characterised by an abrupt mountainous massif with several peaks (Ruivo de Santana, 1861 m; Areeiro, 1811m; Cidrão, 1802m) which are mainly supported by a dense network of unweathered dikes intruded in much lower resistant surrounding rocks. The western block is dominated by a 25km2, 1500m high plateau, the "Paul da Serra", slightly tilted to SW, surrounded by steep slopes and incised by deep valleys (Ribeira da Janela, Ribeira do Seixal, Ribeira da Ponta do Sol, etc). The hydrographic network is at a very young stage, and is characterised by intense vertical incision and low lateral erosion, steep longitudinal profiles and absence of important stream captures. The valleys are usually deep, narrow and with U shaped in cross profiles, the slopes are composed by steep segments cut in weak pyroclastic materials, separated by near vertical scarps in lava flows.
