Spain and Portugal may appear completely stable, but geologists say the Iberian Peninsula is slowly rotating due to powerful forces deep beneath the Earth’s surface. The movement is extremely slow, measured in millimeters per year, and cannot be felt by people.
The Iberian Peninsula is situated on a tectonic plate between the African and Eurasian plates, which are moving toward each other at a rate of 4 to 6 millimeters per year. Unlike other regions where such movement creates clear fault lines or subduction zones, southern Iberia shows a more complex pattern.
A recent study published in Gondwana Research found that the plate boundary in the western Mediterranean is diffuse rather than sharply defined. Instead of stress being released along a single fault, it is distributed across a wide area that includes Spain and Portugal.
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As a result, the Iberian block is not simply shifting northward with Eurasia. Instead, it is slowly rotating clockwise, responding to pressure from both plates.
The Alboran domain, located between southern Spain and northern Morocco, plays a key role. This region is being pushed westward while also experiencing pressure from the south. This sideways movement contributes to the rotation of the peninsula.
These forces helped form the Gibraltar Arc, linking Spain’s Betic mountain ranges with Morocco’s Rif mountains, and explain the complex geology of the Strait of Gibraltar.
Tectonic pressure varies across the region. In some areas, Africa pushes directly into Eurasia, compressing the crust. In others, energy is released laterally, allowing the crust to slide. To the southwest of the Strait of Gibraltar, Africa applies more direct pressure, acting like a piston that promotes rotation.
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Scientists detected this motion using seismic records and satellite GPS measurements, which can identify movements of just a few millimetres per year.
This slow rotation helps explain why earthquakes occur across Spain and Portugal, often away from visible fault lines. While it does not allow earthquakes to be predicted, the research improves understanding of how stress builds up beneath the region.
