Calanque

The best known examples of this formation can be found in the Massif des Calanques (Massís dei calancas in Occitan, the traditional local language) in the Bouches-du-Rhône department of Southern France. The range extends for 20 km (12 mi) in length and four kilometres (2.5 mi) in width along the coast between Marseille and Cassis, culminating in Mont Puget (565 m or 1,854 ft). Similar calanques can also be found on the French Riviera near the Massif de l'Esterel and on the island of Corsica (Calanques de Piana). The highest points along the calanques are located at Mont Puget (565 m or 1,854 ft) and in the mountains of Marseilleveyre (432 m or 1,417 ft).[4] Similarities are seen between calanques and rias, the river mouths formed along the coast of Brittany in Northern France.

The limestone calanques of the Massif des Calanques lie within the recently created Calanques National Park (2012) and include the Calanque de Sormiou, Calanque de Morgiou, Calanque de Port-Miou and Calanque de Sugiton. There are additional calanques in the national park, further east along the coast, incised into Cap Canaille. These calanques formed in different rock strata, often in layers of cemented pebble conglomerate. Calanques are also present in the Italian Apennines, in locations such as the Accona Desert and in the Calanchi natural preserve of Atri.

Calanque d'En-Vau, one of the calanques located in the Calanques National Park

Calanques of Marseille and Cassis as seen from the Sugiton vantage point

Modern day calanques along the Mediterranean Sea are steep-sided valleys that the Holocene (Flandrian) marine transgression partially submerged to form cliff-edged inlets. These valleys were either incised by rivers or created by cave collapse as karstic dry valleys when sea level was lower than at present.[1][2][3]

Along the coast of the Mediterranean Sea, some of the valleys, which were flooded to form calanques, might date back to the Messinian salinity crisis between 5.96 and 5.32 million years ago. During this period of time, the Mediterranean Sea became isolated from the Atlantic Ocean and its surface level dropped as much as 1,500 m (4,900 ft) below the level of the Atlantic Ocean.[5][6] As a result, not only did evaporites accumulate on the abyssal plains of the Mediterranean Sea, but also rivers flowing into it deepened their valleys by hundreds of metres. The Rhône most notably cut a canyon as deep as 576 m (1,890 ft) into Cretaceous carbonate strata near its confluence with its tributary the Ardèche. Fluvial erosion by smaller streams and rivers created numerous other deep, steep-sided valleys in response to the greatly lowered sea level at this time.[7] Also at this time, steep-walled, dry karstic valleys were formed by the collapse of caves that developed in limestone, dolomite, and other carbonate rocks in response to the greatly lowered sea level of the Mediterranean Sea.[8] Later, during the Pleistocene, these valleys were further enlarged and modified by fluvial, karst, and other processes during interglacial drops of sea level within the 100-metre (330 ft) range. During these periods of interglacial low sea level, additional steep-sided valleys, which were later flooded to create calanques, along the Mediterranean coastline were formed by fluvial and karst processes.[9] Today, they can be seen as deep, narrow valleys that are partly submerged by the sea and are made up of limestone or granite.[4]

A typical Calanques cliff with sparse vegetation anchored to it, seen from Mont Puget

Calanques at Vezzano sul Crostolo, Italian Apennines

The calanques have a particular ecosystem, as soil is almost non-existent there, and the limestone cliffs instead contain numerous cracks into which the roots of plants are anchored. Nevertheless, the biota is diverse, with over 900 plant species,[10] including a number of endemics like the Marseille Tragacanth and Sabline de Marseille: members of the Papilionaceae family, which can only be found in the hills of Marseille.[11]

In places where cliffs are less vertical, the vegetation is a classic Mediterranean maquis, typically consisting of densely growing evergreen shrubs such as sage, juniper and myrtle. It is similar to heath in many aspects, but with taller shrubs, typically 2–4 m (6.6–13.1 ft) high as opposed to 0.2–1 m (0.7–3.3 ft) for heath. Like elsewhere on the Mediterranean coast, the Calanques' climate is arid, with moisture during much of the year coming only from the evaporation of the sea. This dry habitat associated with salt spray conditions the subsistence of adapted vegetation. The Calanques shelter rabbits, foxes, large crows and Bonelli's eagles, as well as many reptiles and wild boars.