Throughout the history of Madeira, mass movements have claimed hundreds of victims and caused material damage to the population of the island. Landslides, from the most rapid debris flows and rock falls to the slowest slides and creep movements in talus deposits, are common phenomena. We will focus only on rotational slides in rock material. These slides are the most important in displaced rock volume. Madalena do Mar rotational slide that occurred in the river valley of the Ribeira da Madalena gave origin to a debris flow that killed 4 people and destroyed more than 40 houses. The Arco Pequeno rotational slide, almost 1000 m long, was a slow movement that did not cause any damages. We describe in this paper the Madalena do Mar, Arco Pequeno and Achada (Curral das Freiras) rotational slides
Madeira Island is located in the Atlantic north, 900 Km southwest of Lisbon (Fig. 1). Dating from the Miocene this island of volcanic origin is located in fully oceanic domain interpreted as being the south-western termination of a broad alignment of scattered seamounts and volcanic judges, representing a hotspot track in which Madeira/Desertas volcanic complex is the present location of the 70 Ma old hotspot that formed Porto Santo island, Seine, Ampere, Coral Patch and Ormond seamounts. The subaerial evolution of Madeira can be divided into a voluminous (99.5% of the subareial volume) shield stage (>4.6–0.7 Ma) and a low volume (0.5%) posterosional stage (<0.7Ma). Posterosional volcanism, mainly cider cones, tuff layers and intracanyon lava flows, continued into the Holocene with the last eruptions occurring 6000 years B:P. (Upper Unit) (Geldmacher et al. 2000). It's essentially formed by lavas, ranging in composition from basanites to mugearits, that are cut by significant dyke swarms of variable orientation and composition ranging up to trachytes, (Mata & Munha, 1999), pyroclastic materials (ashes and tuffs) and volcanic breccias. Sedimentary rocks are mainly fluvial and marine gravel and residual-colluvial deposits.
The island's orography is characterised by the presence of a strong relief with altitudes that surpass 1800 m (Pico Ruivo, l862m) and an average altitude of 700m. The geographical localisation of the island together with is high relieves condition a climate of specific characteristics. The orography and the orientation of the hills favour intense convective rainfalls and debris-flows. The average rainfall values vary between 600mm and almost 3000mm in areas of high altitude. The climate is mild with average annual values between 160 and 210 Celsius.
Mass movements are common phenomena in Madeira Island; the intense rainfall that in extreme events can reaches 500mm/day is the main triggering factor. Movements come from rockfalls and rockslides, debris flows and earth flows to creep movements in colluvial residual deposits and anthropogenic slides in waste landfills. Often, rockfalls are transformed in debris-slides and debris flows. In 1803 in Funchal approximately 800 to 1000 people died killed by flash floods and debris flows.