Erosion processes and gravitational mass movements on Trindade Island, Brazil (South Atlantic Ocean)

This study provides the first assessment of non-volcanic geohazards on Trindade Island, a remote South Atlantic territory 1140 km southeast of Brazil. The island's location, climate, relief, lithology, and natural processes like weathering, erosion, and deposition pose significant dangers to habitation and geoheritage. Our focus was on geological-geotechnical mapping to identify gravitational mass movements and erosive processes. Within the six units mapped, two primary contexts were identified. We observed active hydraulic erosion, such as gullies and alluvial fans, on slopes shaped by nephelinite lava flows interlayered with fragmented pyroclastic material. In contrast, phonolitic peak areas and pyroclastic breccia bedrock displayed gravitational mass movement deposits, such as avalanche rocks. Gravitational mass movements triggered by hydrological erosion processes are the main threat. The island's landscape evolution is primarily driven by natural processes, with human influence contributing since colonization. Thus, Trindade Island's landscape is shaped by both natural and anthropogenic factors. This study underscores the need for effective mitigation and protection measures to ensure the safety of Trindade Island's inhabitable areas. Integrating an analytical model and considering temporal variations in rainfall could enhance our understanding of non-volcanic hazards on oceanic islands.