A new active faultline has been identified off the coast of Croatia, where it’s creating new islands in the Adriatic Sea and lifting the Dinaric Alps, which stretch from Slovenia to Albania.

The faultline runs northwest from an offshore location near the ancient Croatian port of Dubrovnik for 200 kilometres beneath the Adriatic. Its activity is building more islands close to the 1,185 existing Dalmatian Islands that belong to Croatia.

According to a team of US and Croatian geographers, the Eurasian plate is colliding with and sliding above the South Adria microplate, a former slab of African plate, causing the Earth’s crust to become folded and lifted to form mountains and islands.

Richard Bennett of the University of Arizona, lead author of a paper published recently in Geology on the subduction of the microplate, had studied the Italian Alps and Apennine mountains before joining Croatian researchers to investigate the geology of the other side of the Adriatic.

Croatian geographers started monitoring the area’s movement in 1994 using a technique called geodesy, which entails fitting and monitoring small GPS units on rocks throughout the region. This enabled them to ‘watch the Earth’s surface bend and buckle in “real time”,’ according to Bennett. They noticed that the Salentina Peninsula (the heel of Italy) was moving towards Croatia at a rate of about four millimetres per year, a process that – in addition to creating new land – could cause natural hazards.

‘There is a potential for large earthquakes, and perhaps tsunamis, but we need more data to understand the potential for hazards,’ Bennett said.