The Azores hotspot is a

volcanic A volcano is a rupture 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 found where tectonic plates a ...

hotspot in the Northern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

. The

Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

is relatively young and is associated with a bathymetric swell, a

gravity anomaly The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity meas ...

and ocean island

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

geochemistry 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 ...

. The Azores hotspot lies just east of the

Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North ...

Geological area

The Azores domain comprises the Azores Plateau and the Azores archipelago (formed of 9 islands extending a distance of 480 km which have been volcanically active for around 7 Myr). The archipelago lies on the lateral branch of the Mid-Atlantic Ridge near the junction of three major tectonic plates; the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

, the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

and the

African Plate The African Plate is a major tectonic plate that includes much of the continent of Africa (except for its easternmost part) and the adjacent oceanic crust to the west and south. It is bounded by the North American Plate and South American Plate ...

. This unique location causes the area to have ridge-hotspot interaction with a variation of volcanic processes.

The Azores Plateau

The Azores archipelago rises from Azores Plateau, which is an area of thickened

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

thought to have formed over the last 20 Mya. Negative velocity

S-wave __NOTOC__ In seismology and other areas involving elastic waves, S waves, secondary waves, or shear waves (sometimes called elastic S waves) are a type of elastic wave and are one of the two main types of elastic body waves, so named because th ...

anomalies have been mapped beneath the Azores in the upper 250–300 km. This has been suggested to be a signature of a plume that created the Azores Plateau. Another theory is that the excess volcanism simply results from excess extension at this unusual

triple junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can ...

Hotspot–ridge relationships

The Mid Atlantic Ridge is a zone of extension that permits magma to rise, forming dikes and surface volcanism. Areas of excess magmatism on the Mid Atlantic Ridge have been called hotspots e.g. the Azores. Gravity field modelling studies have shown that the crustal thickness in this area is 60% greater than normal and the

spreading ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a diver ...

is elevated. The hotspot is asymmetrical (north and south). It is thought that crust at ridges is formed by a combination of processes (magmatic and tectonic) with magma addition coming from short lived

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...

s. The increased melt production within the mantle may have supported a longer lived magma chamber causing the crust to be thicker. However, the Mid Atlantic Ridge has also been shown to have affected the characteristics of the Azores Plateau. It has been suggested that the main volcanic ridges on the plateau were created at the Mid Atlantic Ridge spreading axis.

References

External links

Azores Hotspot Deep SignatureUpper mantle structure beneath the Azores hotspot from finite-frequency seismic tomography
{{Hotspots Hotspots of the Atlantic Ocean Geography of the Azores Geology of the Azores