Italy’s Lower Crust Is “Thawing” and Sinking Into the Mantle, Study Finds

Researchers say the unusual tectonic process is driving much of the seismic activity beneath the Apennine Mountains.

Italy’s underground crust is “thawing” and falling into the mantle, according to a new study. This process may be responsible for much of the seismic activity beneath the Apennines, a long mountain range that runs like a spine through the Italian peninsula.

The region offers a rare opportunity to observe the final stages of subduction — the movement of oceanic crust beneath adjacent continental crust — said study lead author Stefano Tavani, a geoscientist at the University of Florence.

“We are experiencing a very, very late stage of subduction, and the tectonics are being driven by another engine, which is thawing out,” Tavani told Live Science.

Why the Apennines are so tectonically complex

The Mediterranean region between Africa and Eurasia is a patchwork of tectonic microplates and mountain ranges, making its geology especially complex.

The broader picture is shaped by the African Plate pushing northward into the Eurasian Plate. This movement squeezes Earth’s crust while the ancient Tethys Ocean is subducted into the mantle beneath the Apennines. The process has been occurring for about 50 million years.

Subduction has created a push-and-pull of geological forces along the Apennines. As the African Plate moved beneath the Eurasian Plate, the subduction-zone boundary migrated toward the overriding plate. This stretched and thinned the Eurasian crust, helping form two large basins.

One is an older basin in the Mediterranean Sea west of Corsica and Sardinia. The other is the younger Tyrrhenian Sea basin, east of Corsica and Sardinia, which formed about 10 million years ago. The forces driving the basin expansion and the compression that built the Apennines have not been completely clear.

Lower-crust delamination may drive earthquakes

To investigate the region’s unusual tectonic movement, Tavani and his colleagues combined GPS data, satellite measurements of ground motion, seismic records and tectonic models of plate movement.

The researchers found that the lower crust beneath the Apennines is breaking away and sinking into the mantle. This process, known as delamination, appears to cause most of the region’s seismic activity, rather than the direct subduction of one plate beneath another.

The findings were reported in a study published in Communications Earth & Environment. Tavani said the lower crust could be completely shed within a few million years, leaving the two plates welded together.

A late stage of plate tectonics

Similar processes may be occurring elsewhere, including at the Hellenic Trench south of Greece. Tavani said the discovery could apply to several other tectonic systems because it represents a very late stage of plate tectonics.

Study: Tavani, S., Petracchini, L., Billi, A., Carminati, E., Molli, G., Palano, M., Scognamiglio, L., Morgan, J. P., and Vannucchi, P. (2026). “Thawing of the lower crust causes active orogenic deformation.” Communications Earth & Environment.