This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Extending some 1,200 kilometers (750 miles) along the length of Italy, the Apennine Mountains present a challenging puzzle for geologists. In some places, the mountains are steadily being stretched apart, while in regions just tens of kilometers away, they are squeezing together.
Through new research published in Communications Earth & Environment, a team led by Stefano Tavani at the University of Florence has uncovered a likely cause for these mysterious motions. By combining satellite measurements with geological and earthquake data, the researchers confirmed that the deepest layer of Earth's crust beneath the mountains is gradually peeling away and sinking into the hot, slowly flowing mantle below—dragging the landscape above along with it. In the Tyrrhenian Sea to the west of Italy, Earth's crust began to pull apart around 10 million years ago.
In the process, the sea basin became wider and deeper over time, with the crust thinning so much in some places that the seabed met the mantle below. At the same time, a zone of stretching crept steadily eastward toward the Apennines, alongside a zone of squeezing farther ahead. Around 2 million years ago, the Tyrrhenian seafloor stopped opening up—but for reasons that geophysicists have yet to explain, the stretching and squeezing carried on in the mountains.
Based on computer models, some researchers suggested that the crust peeling away beneath the mountains could explain this, but so far, clear evidence has been hard to find. To investigate, Tavani's team gathered precise GPS and satellite measurements of how the ground is moving across Italy and compared them with records of earthquakes and geological maps of structures deep underground. They then compared these patterns with a simple model that described how Earth's crust bends as its deeper layers peel away.
They found that along almost the entire mountain range, earthquakes and active ground movements are clustered in a narrow band sitting directly above an 'unzipping front': the point where the deep crust is currently peeling away. As this front slowly moves eastward, it pulls the crust above it apart while squeezing the rocks ahead of it together. Their model also reproduced how the ground is rising and sinking around the front, showing that peeling alone can explain the pattern of motion across the range.
The results reveal why the Apennines have remained so active long after the neighboring seafloor stopped opening and offer a clearer picture of where Italy's earthquakes are likely to strike in the future. The researchers also suggest that similar peeling processes may be keeping other aging mountain ranges active around the world. Written for you by our author Sam Jarman, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work.
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