The Recent and Submerged Tombolos—Unique Phenomena on the Adriatic Sea

Abstract

Prvić Island (Kvarner area in the NE channel part of the Adriatic Sea) is a part of the Natura 2000 protected area network. A recent tombolo is located on the SW coast of Prvić Island, and much larger submerged tombolos are located on the shoal towards the south. Both phenomena are unique to the Croatian coast of the Adriatic Sea. The inland part of the tombolo was surveyed using an Unmanned Aerial Vehicle, and a 3D point cloud was created using Structure from Motion with Multi-View Stereo photogrammetry. The body of the talus breccia behind the tombolo has a triangular form. Large collapsed rocky blocks form the cape vertex. This cape is in a state of equilibrium in the present oceanographic conditions but might be eroded due to predicted rises in sea level. The submarine zone was explored using scuba-diving equipment and Remotely Operated Vehicles. A large triangle-shaped shoal consists of flysch. Parallel vertical sandstone layers that look like artificially built walls are more than a hundred metres long. The carbonate breccia is located at the end of the shallow zone. The conditions for the final formation of the submerged shoal were created during the sea level stagnation in the Holocene.