• The Capbreton gouf is a huge submarine canyon 300 km long in the Bay of Biscay.

  • More than its length, its particularity is to start just a few hundred meters from the Landes coast.

  • A real spot for marine biodiversity, it is also the one that creates the famous wave of the North of Hossegor.

An almost unique geological exception in the world, the Capbreton gouf is a 300 km long submarine canyon in the Bay of Biscay, which was created by sediments from the Pyrenees.

Starting almost from the Landes coast and opening onto the entire Atlantic Ocean, it is at the heart of the region's marine activities.

Ecological, cultural and scientific heritage, it remains however unknown to the general public.

This is why Ifremer (French Institute for Research for the Exploitation of the Sea) is launching with the Hydrographic and Oceanographic Service of the Navy, and the writer Hugo Verlomme who has been organizing the Journées du Gouf for four years, a game competition to name the main reliefs of this canyon.

The goal will ultimately be to register them on nautical charts.

"To find a name, you should not be afraid to use your imagination by associating it with a shape, an animal, a silhouette, a known or legendary character, an event, a work, an emotion, a relief…" indicates Ifremer.

The competition is open until August 22.

To better understand what this canyon represents,

20 Minutes

interviewed one of the specialists in this marvel of the seabed, the geologist and deputy director of the REM (Physical Resources and Deep Sea Ecosystem) department at Ifremer, Jean-François Bourillet.

Why is this Capbreton gouf so special?

It is not so much its length as its proximity to the coast that makes it special. His head is indeed almost glued to the beach, which is only found in 3% of the submarine canyons in the world. There are 130 canyons in the Bay of Biscay, but the others are 100 or even 150 km from the coast. There, people live in the direct vicinity of this geological anomaly: 100 meters from the edge you already have 100 meters of bottom, it is almost unique. It was also for a long time in direct connection with a whole terrestrial river network, and received the erosion of the Pyrenees by the Adour, which gives it a quite remarkable profile, very rectilinear, like a toboggan of 300 km of long which plunges up to 4,500 meters deep at its end,and with casings [differences between the bottom of the canyon and the top of the flanks] of more than 1,000 meters. But when you look at it from above, it is extremely rounded, with very complicated meanders.

When was it formed?

Most of the canyons of the Bay of Biscay were created during the formation of the Gulf itself, 110 million years ago, when North America and Europe separated.

The Capbreton gouf is more recent.

About 30 million years ago, Africa pushed the Iberian plate against Europe, which created the Pyrenees on one side while more to the west land sank.

The erosion of the Pyrenees then passed through this low point, continuing to dig this canyon for millennia.

So this canyon is constantly evolving?

It evolves all the time, even if nowadays it is no longer by river floods, the Adour no longer throwing itself at the level of Capbreton, but by the littoral drift.

The head of the canyon receives sediments, in this case all the sands that come from the Landes coast, which creates underwater avalanches.

This maintains the bottom of the canyon, but it destabilizes its sides.

What role does it play in the Bay of Biscay?

Deep, cold water rises through the canyon. This mixture of hot and cold water attracts plankton, and therefore fish and large marine mammals [such as whales, sperm whales, large squids, feasts, leatherback turtles…] And this fauna is nearby from the shore, so people can regularly see these marine mammals. And then, it's the gouf that generates the famous wave of La Nord d'Hossegor, which is almost the only rock wave that breaks on a hard bottom, which gives it its own specificity on the whole of the Landes coast. . In addition, an underwater conduit promotes the movement of the swell, which creates a more powerful wave than next to it. The principle is the same for the wave off Nazaré (Portugal).

To participate in the Ifremer game,

go to this link

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