for National Geographic News
A newly identified fault running under the Adriatic Sea is building more of Croatia's Dalmatian Islands and bulking up the Dinaric Alps, a new study says.
Both the islands and the mountain chain—which runs along the upper western coast of the Balkan Peninsula—were believed to have stopped growing 20 million to 30 million years ago.
But scientists found that at the new fault the leading edge of the Eurasian tectonic plate is sliding over the South Adria microplate. (See a map of Earth's tectonic plates.)
"The southern Adria microplate is covered by a thick layer of buoyant rocks called carbonates," said lead researcher Richard A. Bennett of the University of Arizona in Tucson.
"As the Adria plate moves northeast toward Europe, the carbonate layer is scraped off of the microplate, much like snow in front of a snowplow."
Carbonates get piled up on the seafloor in front of the moving plate, forming new islands. Over millions of years the islands are squeezed together like folds in an accordion, which creates new additions to the nearby Dinaric Alps.
What's more, the fault is causing the southern "boot heel" of Italy to move toward the Croatian coast at a rate of about 0.16 inch (0.4 centimeter) a year, while the Adriatic seafloor is sliding under Croatia.
"If this process continues, eventually the seafloor will be completely consumed, bringing Italy into contact with Croatia," Bennett said.
This scenario means the Adriatic Sea could close up in about 50 million to 70 million years.
The new fault spans at least 124 miles (200 kilometers) along the seafloor northwest of Dubrovnik in southern Croatia (see map).
It runs under the Dalmatians, which consist of 1,185 islands off Croatia's coast that have become a popular tourist destination. (See photos of kayaking along the Croatian coast.)
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