ZAP // GEOMAR; Tom Patterson / Wikipedia
Location of the King’s Trough Complex in the Atlantic Ocean
In the depths of the Atlantic Ocean, around 1,000 kilometers off the coast of Portugal, there is a colossal system of underwater canyons — which surpass even the famous Grand Canyon, in the USA, in size. Geologists have now discovered how this depression formed.
Known as King’s Trough Complexthis set of deep trenches and basins, about 500 km long, was not carved by moving water, but by dramatic tectonic forces that once tore up the bottom of the sea.
On land, impressive canyons like the Grand Canyon are carved out over time by river erosion. In the ocean, however, there are no rivers capable of carving the rock on this scale. Still, the seabed is home to gigantic structures that surpass the size of the biggest canyons on land.
About 1,000 km of the Portuguese coast is one of the most striking examples. The King’s Trough Complex spans about 500 km and includes a series of parallel trenches and deep basins. At its eastern end is the Peake Deepone of the deepest points in the Atlantic Ocean.
What gave rise to such an immense formation? In a new study, an international team of researchers, led by the GEOMAR / Helmholtz Center for Ocean Research Kiel, and of which the Portuguese geologist was part Luisa P. Ribeiromember of the Portuguese technical team, has now identified new clues.
The results were presented in an article recently published in Geochemistry, Geophysics, Geosystems.
GEOMAR / Helmholtz Centre for Ocean Research Kiel
“Investigators have long suspected that tectonic processesthat is, the movements of the Earth’s crust, played a central role in the formation of the King’s Trough”, states the main author of the article, Antje Dürkefäldenin GEOMAR.
“Our results now explain, for the first time, why this remarkable structure developed precisely in this location”, adds the GEOMAR marine geologist.
The results of the new study suggest that among 37 and 24 million years delay plate limit that separated Europe and Africa temporarily crossed this area of the North Atlantic. As tectonic plates moved, the crust in this region was stretched and fracturedopening progressively from east to west, like a zip opening.
The formation of this gorge remains a mystery to this day.
One important piece of this puzzle lies even deeper. Before the plate boundary moved into this area, the local oceanic crust had already become unusually thick and hot.
This condition resulted from the rise of hot material from the mantle terrestrial. Known as mantle feather, this persistent column of molten rock originates far below the surface. The research team believes that it was a initial branch of the current Azores mantle plume.
“This thicker and heated crust may have made the region mechanically more fragile, causing the plate boundary to move preferentially towards here”, he explains. Jörg Geldmacher, marine geologist at GEOMAR and co-author of the study. “When this plate boundary later moved south, towards the current Azoresa King’s Trough formation also stopped.”
The King’s Trough is a clear example of how deep mantle processes and plate tectonic movement interact. Activity far below the surface can prepare the crust for later deformation, influencing where large fractures eventually appear and rifts.
These conclusions also help to clarify the geodynamic history widest area of the Atlantic Ocean. Similar processes may still be ongoing today.
This is the case, for example, of Azores regionwhere a comparable trench system known as the Third Rift — and, once again, this is happening in a region with thick oceanic crust, the study authors point out.
