Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

is a volcanic archipelago situated above an oceanic rise that puts the base of the islands above the rest of the seafloor. Cape Verde has been identified as a hotspot and the majority of geoscientists have argued that the archipelago is underlain by a

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic ho ...

and that this plume is responsible for the volcanic activity and associated geothermal anomalies. Evidence for a plume origin includes substantial uplift, low-velocity

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

anomalies in the upper mantle extending to depths of around 500 km, low-velocity anomalies in the lower mantle which appear to pond beneath the transition zone with branches extending to the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

, Canary and Cape Verde hotspots, and petrological,

geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...

, and isotopic evidence which are thought to indicate a deep-mantle source. Some observations, such as a lack of age-progressive volcanism and the geochemical signatures of lavas which indicate a shallow source materials, are inconsistent with the plume model, and some scientists have argued that the Cape Verde Archipelago is a product rather of sub- lithospheric small-scale

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

and instabilities arising from heterogeneities in the

asthenosphere The asthenosphere () is the mechanically weak and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between c. below the surface, and extends as deep as . However, the lower boundary of the asthenosphere i ...

and variations in lithospheric thickness, with the geochemistry of the lavas attributed to remnants of subcontinental lithospheric mantle left in the oceanic lithosphere when the Atlantic Ocean opened. The lack of age progression has been accounted for in the hotspot model by the suggestion it is virtually stationary relative to the lithosphere due to being situated close to the rotational pole of the slowly moving African Plate. The unusual geochemical signatures have been ascribed to recycled oceanic crust and

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...

in the source material. Though Cape Verde's islands are all volcanic in origin, they vary widely in terrain. A still-active volcano on the island of Fogo is the highest point on the archipelago (elevation ).''The Peace Corps Welcomes You to Cape Verde''

Peace Corps The Peace Corps is an Independent agency of the U.S. government, independent agency and program of the United States government that trains and deploys volunteers to communities in partner countries around the world. It was established in Marc ...

(April 2006). ''This article incorporates text from this source, which is in the

public domain The public domain (PD) consists of all the creative work to which no Exclusive exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly Waiver, waived, or may be inapplicable. Because no one holds ...

.'' Extensive salt flats are found on Sal and Maio. On Santiago, Santo Antão, and São Nicolau, arid slopes give way in places to sugarcane fields or banana plantations spread along the base of towering mountains. The islands are geologically principally composed of

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

rocks, with basic volcanics and pyroclastics comprising the majority of the total volume. The

volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...

and

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

ic rocks are distinctly basic in character. The archipelago is an example of a soda-alkaline petrographic province, with a petrologic succession which is similar to that found in other Mid

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

islands. Mount Fogo is an active

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

which most recently erupted in 2014. Fogo's

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

is in diameter, the rim is at an elevation of with an interior cone rising to from the crater's floor level. Calderas probably result from the subsidence, following the partial evacuation of the

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

chamber, of a cylindrical block into the supplying magma chamber, in this case lying at a depth of some . The archipelago has been dated at approximately 180 million years old.Mitchell-Thomé, Raoul C. "Outline of the geology of the Cape Verde Archipelago" Geologische Rundschau, Volume 61, Issue 3, pp. 1087–1109

References

{{Africa topic, Geology of

See also

References