Azores hotspot

The Azores hotspot is a volcanic hotspot located at the Azores in the Northern Atlantic Ocean. A volcanic hotspot is defined as an area of high volcanic activity, a long term source of volcanism. The type of hotspot that characterises the Azores is a relatively young one associated with a bathymetric swell, a gravity anomaly and basalt geochemistry that differs from normal ocean ridge basalts.[1] The Azores hotspot also differs from usual hotspots like Hawaii due the fact that it has interactions with the Mid-Atlantic Ridge, which lies just west of the hotspot. The centre of the hotspot plume has been suggested to be located 100 to 200 km east of the Mid-Atlantic Ridge near the island of Faial.[2]

Hotspots-more
The Azores hotspot is marked 1 on map.

Geological area

The Azores domain comprises the Azores Plateau and the Azores archipelago (formed of 9 islands extending a distance of 480 km) which has been volcanically active for around 7Myr. 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 Eurasian Plate and the African Plate.[3] 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 and is thought to be formed from the Azores hotspot 20 Mya. This has been shown through mapping negative velocity S-wave anomalies beneath the Azores. This has shown that beneath the Azores Plateau there is a negative anomaly limited in the upper 250–300 km which is suggestive to be a signature to a present-day dying plume which would have created the Azores Plateau.[3]

Hotspot–ridge interactions

The Mid Atlantic Ridge offers a different perspective and insight into hotspots. The ridge acts as a cross section through the mantle plume. Anomalies on the Mid Atlantic Ridge have been shown to relate to interactions with the hotspot beneath the Azores. Gravity field modelling studies have shown that the crustal thickness in this area is 60% greater than normal, there is an elevated spreading ridge.[4] The influence of the hotspot on the spreading ridge is mainly asymmetrical to the hotspot (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 chambers.[5] The hotspot is suggested to be responsible of increased melt production within the mantle supporting a longer lived magma chamber causing the crust to be thicker. However, the Mid Atlantic Ridge has also been shown to have effects on the Azores hotspot that effected 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. The interactions between the Mid Atlantic Ridge and the Azores hotspot are responsible for the unique geomorphological characteristics displayed in the Azores Plateau, archipelago and the area of ridge that passes through it.

References

  1. ^ Gente P.; Dyment J.; Maia M.; Goslin J. (2003). "Interaction between the Mid-Atlantic Ridge and the Azores hot spot during the last 85 Myr: Emplacement and rifting of the hot spot-derived plateaus" (PDF). Geochemistry Geophysics Geosystems. 4 (10): 1–23. Bibcode:2003GGG.....4.8514G. doi:10.1029/2003GC000527. Archived from the original (PDF) on 2013-12-20.
  2. ^ Cannat, M.; Briais, A.; Deplus, C.; Escartin, J.; Georgen, J.; Lin, J.; Mercouriev, S.; Meyzen, C.; Muller, M.; Pouliquen, G.; Rabain, A. & da Silva, P. (1999). "Mid-Atlantic Ridge–Azores hotspot interactions: along-axis migration of a hotspot-derived event of enhanced magmatism 10 to 4 Ma ago" (PDF). Earth and Planetary Science Letters. 173 (3): 257–269. Bibcode:1999E&PSL.173..257C. doi:10.1016/S0012-821X(99)00234-4. Archived from the original (PDF) on 2013-12-20.
  3. ^ a b Silveria, G.; Stutzmann, E.; Davaille, A.; Montagner, J.; Mendes-Victor, L. & Sebai, A. (2006). "Azores hotspot signature in the upper mantle" (PDF). Journal of Volcanology and Geothermal Research. 156 (1–2): 23–34. Bibcode:2006JVGR..156...23S. doi:10.1016/j.jvolgeores.2006.03.022.
  4. ^ Bourdon, B.; Langmuir, C. H. & Zinder, A. (1996). "Ridge-hotspot interaction along the Mid-Atlantic Ridge between 37°30′ and 40°30′N: the UTh disequilibrium evidence". Earth and Planetary Science Letters. 142: 175–189. Bibcode:1996E&PSL.142..175B. doi:10.1016/0012-821x(96)00092-1.
  5. ^ Singh, S. C.; Crawford, W. C.; Carton, H.; Seher, T.; Combier, V.; Cannat, M.; Canales, J. P.; Dusunur, D.; Escartin, J. & Miranda, M. (2006). "Discovery of a magma chamber and faults beneath a Mid-Atlantic Ridge hydrothermal field" (PDF). Nature. 442 (7106): 1029–1032. Bibcode:2006Natur.442.1029S. doi:10.1038/nature05105. PMID 16943836. Archived from the original (PDF) on 2013-12-20.

External links

Azores

The Azores ( ə-ZORZ, also US: AY-zorz; Portuguese: Açores [ɐˈsoɾɨʃ]), officially the Autonomous Region of the Azores (Região Autónoma dos Açores), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the North Atlantic Ocean about 1,360 km (850 mi) west of continental Portugal, about 1,500 km (930 mi) west of Lisbon, in continental Portugal, about 1,500 km (930 mi) northwest of Morocco, and about 2,500 km (1,600 mi) southeast of Newfoundland, Canada.

Its main industries are agriculture, dairy farming, livestock, fishing, and tourism, which is becoming the major service activity in the region. In addition, the government of the Azores employs a large percentage of the population directly or indirectly in the service and tertiary sectors. The main city of the Azores is Ponta Delgada.

There are nine major Azorean islands and an islet cluster, in three main groups. These are Flores and Corvo, to the west; Graciosa, Terceira, São Jorge, Pico, and Faial in the centre; and São Miguel, Santa Maria, and the Formigas Reef to the east. They extend for more than 600 km (370 mi) and lie in a northwest-southeast direction.

All the islands have volcanic origins, although some, such as Santa Maria, have had no recorded activity since the islands were settled. Mount Pico, on the island of Pico, is the highest point in Portugal, at 2,351 m (7,713 ft). If measured from their base at the bottom of the ocean to their peaks, which thrust high above the surface of the Atlantic, the Azores are actually some of the tallest mountains on the planet.

The climate of the Azores is very mild for such a northerly location, being influenced by its distance from the continents and by the passing Gulf Stream. Due to the marine influence, temperatures remain mild year-round. Daytime temperatures normally fluctuate between 16 °C (61 °F) and 25 °C (77 °F) depending on season. Temperatures above 30 °C (86 °F) or below 3 °C (37 °F) are unknown in the major population centres. It is also generally wet and cloudy.

The culture, dialect, cuisine, and traditions of the Azorean islands vary considerably, because these once-uninhabited and remote islands were settled sporadically over a span of two centuries.

Azores Plateau

The Azores Plateau or Azores Platform is an oceanic plateau encompassing the Azores archipelago and the Azores Triple Junction in the North Atlantic Ocean. It was formed by the Azores hotspot 20 million years ago and is still associated with active volcanism.The plateau consists of a roughly triangular-shaped large igneous province that lies less than 2,000 m (6,600 ft) below sea level.

Hotspot (geology)

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

Newfoundland Seamounts

The Newfoundland Seamounts are a group of seamounts offshore of Eastern Canada in the northern Atlantic Ocean. Named for the island of Newfoundland, this group of seamounts formed during the Cretaceous period and are poorly studied.The Newfoundland Seamounts appear to have formed as a result of the North American Plate passing over the Azores hotspot. Scruncheon Seamount in the middle of the chain has given an isotopic date of 97.7 ± 1.5 million years for the Newfoundland Seamounts. This indicates that the Newfoundland Seamounts were volcanically active in the earliest Cenomanian stage.

Terceira Rift

The Terceira Rift is a geological rift located amidst the Azores islands in the Atlantic Ocean. It runs between the Azores Triple Junction to the west and the Azores–Gibraltar Transform Fault to the southeast. It separates the Eurasian Plate to the north from the African Plate to the south. The Terceira Rift is named for Terceira Island through which it passes.

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