Stephanie Edwards is the Engagement Specialist at Discover Magazine, who manages all social media platforms and writes digital articles that focus on archaeology, the environment, and public health.
Beneath the rolling surface of the North Atlantic lies a geological structure so vast it rivals the Grand Canyon. Known as the King’s Trough Complex, this enormous system of deep trenches stretches roughly 300 miles across the ocean floor and is located off the coast of Portugal. At its eastern edge sits Peake Deep, one of the deepest known points in the Atlantic Ocean.
Unlike canyons on land, which are carved over time by flowing water, the ocean lacks a comparable erosive force. That makes features like King’s Trough especially puzzling. How did such a colossal underwater canyon form?
A new study published in Geochemistry, Geophysics, Geosystems offers the clearest explanation yet, tying the trough’s origins to a rare combination of shifting tectonic plates and heat rising from deep within the Earth’s mantle.
“Researchers have long suspected that tectonic processes — that is, movements of the Earth’s crust — played a central role in the formation of the King’s Trough. Our results now explain for the first time why this remarkable structure developed precisely at this location,” said lead author Antje Dürkefälden in a press release.
A researcher slices into a volcanic rock sample recovered from several thousand meters below King’s Trough.
(Image Credit: Fabian Hampel, GEOMAR)
What Is the King’s Trough?
King’s Trough is not a single canyon but a complex network of parallel trenches and deep basins carved into the oceanic crust. Together, these features form one of the largest submarine canyon systems on the planet. Its scale alone sets it apart, but its location — far from continental margins and typical tectonic boundaries — has long made it difficult to explain.
For decades, scientists debated whether volcanism, faulting, or some unknown erosional process was responsible. The new research suggests the answer lies in a brief but dramatic episode in the Atlantic’s tectonic history, when the boundary between the African and European plates passed directly through this region.
How Did the King’s Trough Form?
According to the study, between roughly 37 and 24 million years ago, a plate boundary temporarily cut across the North Atlantic where King’s Trough now lies. As the plates pulled apart, the crust stretched and fractured, opening progressively from east to west — a process the researchers liken to a zipper being undone.
What made this zone especially vulnerable was what lay beneath it. Long before the plate boundary appeared, hot material had been rising from deep within the mantle, thickening and heating the oceanic crust from below.
“This thickened, heated crust may have made the region mechanically weaker, so that the plate boundary preferentially shifted here,” explained co-author Jörg Geldmacher. “When the plate boundary later moved further south towards the modern Azores, the formation of the King’s Trough also came to a halt.”
Why This Discovery Matters Today
King’s Trough offers more than a glimpse into the Atlantic’s past. It provides an example of how deep-mantle processes and surface plate motions are intimately connected, and how ancient mantle activity can shape where future tectonic deformations occur.
In the Azores region today, a similar trench system called the Terceira Rift is actively forming in unusually thick oceanic crust, echoing the conditions that once created King’s Trough.
The team based its findings on data collected during a 2020 research expedition, where they used high-resolution sonar to map the seafloor and dredged volcanic rocks from the trenches for chemical analysis. Together, the results help clarify how some of Earth’s most dramatic landscapes came into being.
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Stephanie Edwards is the Engagement Specialist at Discover Magazine, who manages all social media platforms and writes digital articles that focus on archaeology, the environment, and public health.View Full Profile
