Iberian Peninsula rotates clockwise by a few millimeters a year, Gondwana Research study finds

An international team of scientists reports that the Iberian Peninsula, home to Spain and Portugal, is slowly rotating clockwise under the pressure of the African Plate, ua.news writes, citing Futura-sciences and a study in Gondwana Research. The speed is a few millimeters per year. The direction is opposite to that of the previous stage of the region's geological history. ua.newsua.newsua.newsOpen source ↗

The authors combined satellite geodetic measurements with earthquake data. They analyzed crustal movements and stresses within the crust to reconstruct the current pattern of deformation. The rotation is most pronounced in the western and southwestern parts of the peninsula.

Why the rotation changed direction

Africa and Eurasia continue to converge at about 4–6 millimeters per year, according to Asier Madarieta of the University of the Basque Country. West of the Strait of Gibraltar, the African Plate transmits compressional forces to the periphery of the Iberian block. Farther east, part of the deformation is taken up by the crust of the Gibraltar Arc and the adjacent Alboran region.

The boundary between the plates is clearly visible in the Atlantic and near Algeria, but south of Spain and Portugal it becomes considerably more complex. The Gibraltar Arc, a curved structure around the Strait of Gibraltar, lies in a zone of complex deformation and is particularly hard to study.

Earlier history of the Iberian block

Before the North Atlantic opened, the lands of present-day Spain and Portugal were joined to what is now the western coast of France. As the Atlantic opened, the Iberian block separated from Eurasia, and oceanic spreading along the French margin contributed to the formation of the Bay of Biscay. ua.newsua.newsua.newsOpen source ↗ The new microplate moved southwestward while rotating counterclockwise, and interaction with neighboring plates shifted it about 200 kilometers east.

The Alpine orogeny began roughly 90 million years ago, at the end of the Cretaceous. Africa changed its direction of movement, subduction closed the Tethys Ocean, and about 30 million years ago the collision of Africa and Europe formed the Alps. Later the same process pressed the Iberian block against Europe and contributed to the formation of the Pyrenees.

According to the authors, the results help to better understand the active tectonic structures at the Europe–Africa boundary. The data may also serve as a basis for further study of active faults and for a more accurate assessment of seismic hazard in the region, particularly in the Pyrenees.