Geology of Cape Verde - AbsoluteAstronomy.com

The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...

is a volcanic archipelago situated above an oceanic rise that puts the base of the islands 2 km above the rest of the seafloor. Cape Verde has been identified as a hotspot

Hotspot (geology)

The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...

and it has been argued that a mantle plume

Mantle plume

A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...

might be underneath it causing the volcanic activity and associated geothermal

Geothermal

Geothermal is related to energy and may refer to:* The geothermal gradient and associated heat flows from within the Earth- Renewable technology :...

anomalies.

Though Cape Verde's islands are all volcanic in origin, they vary widely in terrain. A still-active volcano on the island of Fogo

Mount Fogo

Pico do Fogo is the highest peak of Cape Verde, rising to above sea level. It is an active stratovolcano lying on the island of Fogo. The main cone last erupted in 1675, causing mass emigration from the island, while a subsidiary vent erupted in 1995...

is the highest point on the archipelago (elevation 2829 metres (9,281 ft)). 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 rocks, with basic volcanics and pyroclastics comprising the majority of the total volume. The volcanic and pluton

Pluton

A pluton in geology is a body of intrusive igneous rock that crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, dikes, sills, laccoliths, lopoliths, and other igneous bodies...

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 islands.
Mount Fogo

Mount Fogo

is an active volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

which most recently erupted in 1995. Fogo’s caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

is 8 km (5 mi) in diameter, the rim is at an elevation of 1600 m (5,249 ft) with an interior cone rising to 2830 m (9,285 ft) from the crater's floor level. Calderas probably result from the subsidence, following the partial evacuation of the magma

Magma

Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

chamber, of a cylindrical block into the supplying magma chamber, in this case lying at a depth of some 8 km (5 mi).
The archipelago has been dated at approximately 180 million years old.

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