The Cres-Losinj group of islands, situated in the Kvarner Gulf, is the largest group in the Adriatic. It is made up of 36 islands, islets and reefs.
The cause underlying the formation and current appearance of the islands of the Kvarner was the transgression of the Adriatic Sea in the last 12-6 thousand years.
Some 20-30 thousand years ago the whole Kvarner underwent elevation, including northern Dalmatia and the Italian coast of the Adriatic. With the melting of the icebergs, at the end of the Ice Age, there was a rise in the level of the Adriatic Sea of about 100m, and the mountains and hills of the mainland became islands, the higher hills became smaller islands and the lower hills became underwater reefs and rocks.
Cres and Losinj, with their neighboring islands and islets, are a continuation of the Cicarija mountain range, that is, of its southern extension - Ucka. The extension of the highest part of the Ucka range can be connected with the range to the north of Cres (Sis - 638m). The southern part of the Ucka range (Sisol - 833m), via the cape of Masnjak, extends to the cape of Pernat onto the chain of hills west of the Vrana Lake (Helm - 483m), and further south to Losinj, via Osorscica (Mount Osor - Televrina - 588m), to finally end on the island of Ilovik. The extension of the hilly formation south of Labin is breifly suggested by the islands of Unije and Srakane (N. Strazicic, 1975).
Chalk limestone and dolomite of very diverse content and resistance is dominant in the geological composition of the islands. This played an essential role in the forming of the present relief. Thus a more compact and purer limestone, recognizable by its craggy and rugged rock, is located on the island of Cres near Beli, in Lubenice, and on the island of Losinj, in the mountain mass of Osorscica. The locations of impure limestone, mixed with dolomite, is where valleys were formed due to erosion. Examples of this are the valleys where the town of Cres or the settlement of Martinscica are located. Dolomites in which the greatest breakdown and erosion is taking place are located in the entire area surrounding Vrana Lake as well the entire stretch tot the southeastern point of the island of Cres. Here the coastline is very indented and forms fjords which deeply cut into the land, for example, the points of St. Dumjan and Kolorat or the deeply indented Jadriscica Bay. This phenomenon can also be seen around the port of Mali Losinj.
On the islands of Susak, Male and Vele Srakane and on the southwestern part of the island of Unije (Polje) one encounters layers of sand originating from the loess type of limestone base. The wind-blown deposits of sand were brought here prior to the rise of the sea level by the cold winds that shoveled it up from the river deposits to lay it on the mountains that then stood there.
As a point of interest we quote the latest data regarding the areas of the islands of the Kvarner Gulf. Until recently, the island of Cres was considered the second largest island of the Adriatic, right after Krk. The newest measurements, however, show that the islands of Cres and Krk are identical in area, exactly 405,78 sq. km each. This is certainly a unique case of 2 neighboring islands being of identical size. Due to the annual rise of the sea-level of about 1 mm, the area of the islands is slowly decreasing. This process is faster on Krk because of its tamer coast. So, it may be said that 20 years from now, Cres will be the largest island of the Adriatic.
The Gulf of Kvarner is, second to the Gulf of Trieste, is the deepest indentation into the European mainland. The Gate of Postojna, in the immediate hinterland, is the most important passage from the European hinterland to the Adriatic Sea, whereas the Gate of Delnice is the passage from the Danube valley basin (Podunavlje). That is why this group of islands has always been of great importance regarding traffic.
The "Amber Route" crossed our islands and was used by merchants who brought amber, spices, silk, etc. from the East. Apsyrtides Nesoi, the Greek name for these islands, tells us that the main settlement here was APSOROS, today's Osor.
The man-made strait, which now separates the islands of Cres and Losinj, probably dates back to the Roman period of rule here, when it was of great strategic and commercial importance because of the ways of navigation in those times.
As of the 14th century, tho role of the island's center was taken over by the town of Crepsa, today's Cres. One of the reasons was that up to then seamen sailed only with "fair" winds, that is, winds astern. Being that the winds of this area often change directions, coming from the southern quadrant: Levant (eastern), Jugo (southeastern) and Scirocco (southern) and those from the northern quadrant: the Bora (northeastern), the Tramontana (northern) and the Mistral. Ships kept close to the shores of our islands and their many bays and inlets sheltered the boats from bad weather and storms.
With the development of seamanship and building of larger, more modern ships, which could spite the sea's storms, and because if its geographical location and the size of its harbor, which could hold such ships, Mali Losinj became the island's center in the 19th century.
With the advent of the steamboat and tourism, the Cres-Losinj group of islands that were once of great navigational significance will change this role and become famous tourist destinations.