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| Ilhéu Raso | |
|---|---|
| Name | Ilhéu Raso |
| Location | Atlantic Ocean |
| Archipelago | Cape Verde |
| Area km2 | 5.76 |
| Highest mount | Topo |
| Elevation m | 164 |
| Country | Cape Verde |
Ilhéu Raso Ilhéu Raso is a small uninhabited volcanic islet in the central group of the Cape Verde archipelago, located near São Nicolau and Brava, and administered by the municipality of São Vicente, Cape Verde. The islet lies within the Ilhas do Sotavento maritime zone and forms part of the Ilhas Selvagens bio-geographic region, attracting attention from biogeography researchers, ornithology groups, and conservation agencies concerned with North Atlantic island endemism.
Ilhéu Raso sits in the central Atlantic between Santo Antão, Cape Verde and Fogo, Cape Verde, roughly 17 km from Santa Luzia, Cape Verde and 40 km from Sal, Cape Verde, with steep basaltic cliffs rising to about 164 m above sea level near its summit Topo, and a coastline defined by rocky headlands, sea stacks, and small coves. Nautical charts produced by Hydrographic Office (United Kingdom) collaborators and regional surveys by the Instituto Nacional de Investigação e Desenvolvimento Agrário (INIDA) and Direcção Geral do Ambiente (DGA) show bathymetric shelves, underwater lava flows, and prevailing currents influenced by the Canary Current and seasonal trade winds from the Azores High.
The islet is a remnant of Pleistocene and Holocene volcanic activity associated with the Cape Verde hotspot, sharing petrological affinities with lavas on São Vicente, Cape Verde, Santo Antão, Cape Verde, and Fogo, Cape Verde, and its basaltic composition records fractional crystallization and mantle plume processes studied by teams from University of Lisbon, Universidade de Cabo Verde, and the Instituto Superior Técnico. Geological mapping links its stratigraphy to submarine eruptions, phonolitic dikes, and tuff rings similar to features documented on Pico do Fogo and Monte Verde (São Vicente), and radiometric dating by radiocarbon dating and 40Ar/39Ar dating methods constrains eruption sequences relevant to Atlantic hotspot models advanced by researchers at National Oceanography Centre and Woods Hole Oceanographic Institution.
The sparse terrestrial flora includes xerophytic shrubs and lichens comparable to assemblages on Boa Vista, Cape Verde and Santo Antão, Cape Verde, with studies by botanists from Jardim Botânico Nacional (Cape Verde) and Royal Botanic Gardens, Kew documenting endemic and Macaronesian-affiliated taxa. Ilhéu Raso is internationally notable for seabird colonies, including historic nesting by Cory's shearwater and Band-rumped storm petrel analogs, and it was the type locality for the now-extinct Raso lark, a specialist studied by ornithologists from BirdLife International, Royal Society for the Protection of Birds, and university groups at University of Oxford and University of Cambridge. Marine fauna in adjacent waters hosts cetaceans monitored by Society for Marine Mammalogy researchers and reef fish assemblages surveyed by teams associated with Conservation International and the World Wildlife Fund.
Mariners from Portuguese Empire expeditions in the 15th century first charted many Cape Verde islets; later hydrographic surveys by the British Admiralty and explorers associated with Vasco da Gama-era routes recorded the islet as a navigational hazard for sailing ships and whalers from New England and Basque Country. Scientific visits during the 19th and 20th centuries included naturalists linked to Charles Darwin-inspired studies, expeditions organized by Museu Nacional de História Natural (Lisbon), and post-war surveys by the International Council for Bird Preservation that documented breeding colonies and specimen collections now held in institutions such as the Natural History Museum, London and Museu de História Natural do Funchal.
Ilhéu Raso is part of specially protected areas designated under national decrees administered by the Ministry of Agriculture and Environment (Cape Verde) and international instruments promoted by UNEP and IUCN, forming part of a marine-protected network emphasized in programmes supported by the European Union and Global Environment Facility. Conservation plans developed with input from BirdLife International, Conservation International, and Cape Verdean NGOs aim to protect endangered species like the Raso lark and to control invasive rodents following eradication precedents on South Georgia and Gough Island. Monitoring and habitat restoration projects have drawn funding and technical assistance from the Darwin Initiative and research collaborations with University of Lisbon and University of Cape Town.
Access to the islet is restricted and typically requires permits issued by Cape Verdean authorities including the Direcção Geral do Ambiente and local municipal offices in São Vicente, Cape Verde, with logistical support provided by research vessels from institutions such as IMAR — Instituto do Mar and charter companies operating out of Mindelo. Navigation to the islet demands careful passage planning using charts from the UK Hydrographic Office, awareness of local swell and wind conditions influenced by the North Atlantic Oscillation, and compliance with protected-area protocols enforced by national law and international conservation agreements.