Descent of the Canyon

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Ascent of the Canyon

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Nazaré Canyon

A submarine canyon corresponds, in sub aerial conditions, to a river affected by currents, sediment transport and erosion phenomena.
However, in the case of submarine canyons, all this processes occur under water where dynamics are different, acting as sedimentary conduits through which there is a magnification of the transport processes between the coastal zone and the deep oceanic domain.

Canhão Submarino da Nazaré

In the case of the Nazaré canyon, the fact that its head is situated near shore causes a significant influence into the hydrodynamic and sediment transport processes leading to particular oceanographic conditions, intrinsically connected with its morphology.

Considered the longest in Europe, this submarine canyon, dissects the Iberian margin in an east-west direction, from the continental shelf, at 50 meters depth, extending to the Iberian abyssal plain at approximately the 5000 meters depth. Depending on the continental margin region crossed by the canyon it is possible to distinguish 3 sections.

The upper section comprises the part that cuts the continental shelf. Its border, near shore – the canyon head - is situated at less than 1 km SW of the Sítio da Nazaré, at 50 meters depth, diving to greater depths for 60 km, until it reaches the continental shelf break.
In this sector the canyon presents a V – shaped axis dissected by several gullies.

The following section, the middle section of the canyon, corresponds to the cut in the continental slope. This section begins in the shelf border and extends, beyond 57 km, to the continental slope base, reaching the 4050 meters depth.
Throughout this section the canyon conserves the V – shaped morphology, it is very sinuous and presents numerous large gullies on the deepest part which defines its channel axis (thalweg).

The lower canyon section corresponds to the deepest part of the canyon and it is located at depths greater than 4050 meters. This section extends for 94 km. Here, the central part of the canyon – the thalweg – loses its abrupt characteristics present in the less deeper sections, changing its V – shape morphology into a flat-bottomed shape. At 4970 meters depth, 211 km from de canyon head, the canyon reaches the Iberian abyssal plain.

 
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