Continental shelves/North west African continental shelves

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The image shows a portion of the northwest African continental margin. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.

There is an apparently small continental shelf along the northwest African coast.

Iberian margins[edit]

This bathymetry map locates major seamounts between Madeira and Iberia. Credit: ELLA links.
The image shows the many islands, seamounts and ocean floor plateaus of the Iberian margins. Credit: Russell Wynn and Bryan Cronin.
The image shows the topography and bathymetry west of Iberia. Credit: C. Cramez.
Color shaded relief map of the southwest Iberian Margin includes land topography and bathymetry. Credit: Gerassimos A. Papadopoulos, Eulàlia Gràcia, Roger Urgeles, Valenti Sallares, Paolo Marco De Martini, Daniela Pantosti, Mauricio González, Ahmet C. Yalciner, Jean Mascle, Dimitris Sakellariou, Amos Salamon, Stefano Tinti, Vassilis Karastathis, Anna Fokaefs, Angelo Camerlenghi, Tatyana Novikova, and Antonia Papageorgiou.

In the images on the left, sea level during the last glaciation is likely at or above the yellow contour band. This appears to be the sea level delimiter in the second image down on the right.

Moroccan shelves[edit]

The image is a relative color-coded topographic map of the northern portion of the Moroccan shelf. Credit: Muawia Barazangi.
This elevation map shows the southern portion of the Moroccan shelf. Credit: Colleen McMahon, Macquarie University.

The first image on the right shows a currently submerged mountain range and associated islands directly in front of the Pillars of Hercules just further west. These may have been above sea level during the previous 50 kyrs ice age.

Mauritanian continental shelves[edit]

The image shows bathymetry of the Mauritanian and Senegambian continental shelves. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.

The "sedimentary processes along the shelf are driven by long-term factors such as Quaternary glacial–interglacial periods and shelf morphology, and by short-term factors such as fluvial and aeolian sediment supply, local climate (temperature, rainfall and wind) and hydrodynamic conditions (tides, swell, longshore current, the Canary Current and upwelling)."[1]

Canary Island seamount province[edit]

The Canary Island Seamount Province (CISP) comprises more than 100 seamounts. Credit: Paul van den Bogaard.

"The Canary Island Seamount Province forms a scattered hotspot track on the Atlantic ocean floor ~1300 km long and ~350 km wide, perpendicular to lithospheric fractures, and parallel to the NW African continental margin. New 40Ar/39Ar datings show that seamount ages vary from 133 Ma to 0.2 Ma in the central archipelago, and from 142 Ma to 91 Ma in the southwest."[2]

Shallow "mantle upwelling beneath the Atlantic Ocean basin off the NW African continental lithosphere flanks produced recurrent melting anomalies and seamounts from the Late Jurassic to Recent".[2]

Azores microplates[edit]

The diagram shows the Azores current as it is deflected by the islands from the Gulf stream. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.
One of the 140 pyramids is imaged and observed by archeologists in the Madalena area of Pico Island, Azores. Credit: Carolina Matos.
The Azores are nine islands that occupy a triple junction between the North American, African and Eurasian Plate. It is a spreading center bound by the Mid-Atlantic Ridge on the west and the Terceira Rift on the NE and the East Azores Fracture Zone to the SE. Credit: Lourenço et al.
Map of the Azores archipelago and adjacent region shows all nine islands (western group: Flores and Corvo; central group: Terceira, Graciosa, Sao Jorge (SJ), Pico, and Faial; eastern group: Sao Miguel, and Santa Maria). Credit: Yang et al.
This image was taken from Flores of the island of Corvo to the north. Credit: C. Beier.

"Archaeologists from the Portuguese Association of Archaeological Research (APIA) have identified [a great variety of protohistoric pyramidal rock structures, some of them 13 meters tall] on Pico island that supports their belief that human occupation of the Azores predates the arrival of the Portuguese by many thousands of years."[3]

The "Madalena pyramidal structures, known by the locals as “maroiços,” are analogous to similar protohistoric structures found in Sicily, North Africa and the Canary islands which are known to have served ritual purposes."[3]

The diagram on the right shows the Azores current as it is deflected by the islands from the Gulf stream about 2014.

The second image down on the right shows the Azores as nine islands that occupy a triple junction between the North American, African and Eurasian Plate, a spreading center bound by the Mid-Atlantic Ridge on the west and the Terceira Rift on the NE and the East Azores Fracture Zone to the SE. From the structure shown, the microplate though thick has undergone extensive fracturing. If at one time it was at or near sea level, it could have blocked a significant portion of the Gulf stream, diverted a major portion toward northwest Africa, or diverted most of the stream north of Scotland into the Norwegian coast. The microplate likely broke apart and subsided in a west to east manner.

The second image on the left is a more geostructurally detailed topographic map of the entire Azores microplate. It clearly shows how the forming of the Mid-Atlantic Ridge underneath has torn the microplate apart along the ridge and approximately perpendicular to it. The orange to brown band is the 1,000 m to sea level band. White is currently above sea level. The yellow band is the 2,000 m to 1,000 m band. It surrounds much of the brown zone and suggests an almost square plateau.

The third image down on the left shows two rows or walls of similarly sized volcanic rock crossing the field of view like those used to make the Pico pyramids.

North Atlantic Ridge[edit]

Surface of the Earth, 2 minute bathymetry/topography selection is sized at 45 degrees by 45 degrees. Credit: NCEI (formerly NGDC).

The image on the right shows the topography west of north western Africa out to the Mid-Atlantic Ridge. It clearly shows the impact the ridge had on the Azores microplate, breaking it into parts on either side of the ridge.

See also[edit]

References[edit]

  1. Nadia Mhammdi, Maria Snoussi, Fida Medina, and El Bachir Jaaïdi (2014). "Recent sedimentation in the NW African shelf". Geological Society, London, Memoirs 41: 131-146. doi:10.1144/M41.10. https://www.researchgate.net/profile/Nadia_Mhammdi/publication/283944649_Mhammdietal2014GSL/links/564a459a08ae9cd9c826b186.pdf. Retrieved 2017-04-27. 
  2. 2.0 2.1 Paul van den Bogaard (2013). "The origin of the Canary Island Seamount Province - New ages of old seamounts". Scientific Reports 3: 2107. doi:10.1038/srep02107. https://www.nature.com/articles/srep02107. Retrieved 2017-04-27. 
  3. 3.0 3.1 Carolina Matos (28 August 2013). Pico: New archaeological evidence reveals human presence before Portuguese occupation – Azores. Portuguese American Journal. Retrieved 2017-04-27.