Scientists have revealed that a hidden mantle plume contributed to the formation of the King's Trough Complex, a vast underwater canyon system in the North Atlantic larger than the Grand Canyon. Located about 1,000 kilometers off Portugal's coast, this 500-kilometer structure resulted from tectonic rifting between Europe and Africa millions of years ago. The findings, based on rock samples and seafloor mapping, highlight how deep Earth processes influence ocean floor features.
The King's Trough Complex stretches roughly 500 kilometers and features parallel trenches and deep basins, with Peake Deep marking one of the Atlantic's deepest points at its eastern edge. Unlike land canyons eroded by rivers, this oceanic formation arose from tectonic movements rather than water flow.
A study led by researchers from the GEOMAR Helmholtz Centre for Ocean Research Kiel explains its origin. Between 37 and 24 million years ago, a transient plate boundary separating Europe and Africa shifted through the region, pulling the crust apart from east to west. Prior to this, the oceanic crust had thickened and heated due to a mantle plume—a column of hot material rising from deep within Earth. This plume is considered an early branch of the current Azores mantle plume, which weakened the crust and directed the rifting there.
"Our results now explain for the first time why this remarkable structure developed precisely at this location," stated lead author Dr. Antje Dürkefälden, a marine geologist at GEOMAR. Co-author PD Dr. Jörg Geldmacher added, "This thickened, heated crust may have made the region mechanically weaker, so that the plate boundary preferentially shifted here."
The research drew on data from the 2020 expedition M168 aboard the research vessel METEOR. The team used high-resolution sonar for seafloor mapping and collected volcanic rock samples via dredge. Laboratory analysis of the rocks' chemistry and ages, conducted at institutions including the University of Madison in Wisconsin, supported the timeline. Additional bathymetric data came from Portugal's Estrutura de Missão para a Extensão da Plataforma Continental (EMEPC), with contributions from Kiel University and Martin Luther University Halle-Wittenberg.
These insights illustrate interactions between mantle activity and plate tectonics in the Atlantic. A similar process may be active today near the Azores, where the Terceira Rift is developing in thickened crust. The study appears in Geochemistry, Geophysics, Geosystems.