Something unusual is happening deep beneath Italy, where a hidden layer of Earth’s crust appears to be peeling away and sinking into the mantle. Scientists say this slow-motion geological process, known as delamination, may be responsible for much of the earthquake activity along the Apennine Mountains. The discovery offers a new look at what is happening beneath one of Europe’s most seismically active regions and could change how researchers understand its restless geology.
Deep beneath Italy’s Apennine Mountains, a section of Earth’s crust is slowly breaking away and sinking into the mantle. Researchers say this previously overlooked process may be responsible for much of the seismic activity affecting the region.
The Apennines stretch down the Italian peninsula like a spine and offer scientists a rare opportunity to study the final stages of a process known as subduction. This happens when one tectonic plate moves beneath another and sinks into Earth’s mantle.
But according to study lead author Stefano Tavani, a geoscientist at the University of Florence, the tectonic forces beneath Italy are now being driven by something different.
“We are experiencing the very, very late-stage to the subduction, and the tectonics is driven by a different engine, which is this unzipping,” Tavani told Live Science.
How Italy’s complicated geology took shape
The area around the Mediterranean is one of the most complicated tectonic regions on Earth. Africa and Eurasia are surrounded by a collection of smaller tectonic plates and mountain ranges, creating a constantly shifting geological landscape.
At the broadest level, much of this activity can be traced to the African plate moving northward toward Eurasia. Over roughly 50 million years, this movement has squeezed the Earth’s crust while helping drive an ancient ocean known as the Tethys beneath the region and into the mantle.
That long-running collision helped shape the Apennines. But the movement of the plates also produced forces pulling the crust in different directions.
As the African plate continued to move beneath the Eurasian plate, the subduction zone itself migrated toward Africa. This movement stretched and thinned the Eurasian crust, contributing to the formation of two major basins in the Mediterranean.
One is an older basin located west of Corsica and Sardinia. The other is the younger Tyrrhenian Sea, east of the islands, which formed around 10 million years ago.
For years, however, scientists have not had a complete explanation for what was driving both the stretching that formed these basins and the compression responsible for building the Apennines.
Scientists find the missing piece
To investigate the forces at work beneath Italy, Tavani and his colleagues combined several types of evidence. They examined earthquake records and measurements of ground movement gathered through GPS and satellites, then compared those observations with models showing how the tectonic plates have moved.
The results pointed to a surprising process taking place deep underground.
Rather than simply being pulled downward as part of traditional plate subduction, the lower portion of the crust beneath the Apennines appears to be peeling away and sinking into the mantle. Scientists call this process delamination.
The researchers concluded that this crustal delamination, rather than plate subduction itself, is responsible for much of the seismic activity in the Apennines.
Their findings were published in Communications Earth & Environment.
The crust could eventually disappear
The geological process unfolding beneath Italy is not expected to continue forever. Tavani said that over the next few million years, the lower crust should finish separating and sinking into the mantle.
Once that happens, the two tectonic plates could eventually weld together, marking another major stage in the region’s long geological evolution.
The discovery also suggests that Italy may not be the only place where this kind of tectonic transition is occurring.
Similar processes are taking place in other parts of the world, including the Hellenic trench south of Greece. Tavani said the findings “could be applied to several other systems,” adding, “because in the end, it is a kind of very late-stage plate tectonics.”
For scientists, the process beneath Italy provides a rare glimpse of what happens when a subduction system approaches the end of its life, and how Earth’s crust can continue reshaping the surface long after a tectonic process appears to be winding down.