Geoturism Balearic Islands

The north part of Formentera is mainly formed by two depressed lagoons called Estany Pudent and Estany des Peix. The latter seems to originate from a karstic collapse favoured by a system of normal faults. The origin of its big brother, S’Estany Pudent, was probably the same. This makes them a place of unique interest. 

The faults on the island are due to tectonic activity after the Alpine Orogeny, which is the predominant orogeny in the Balearic Islands. As a result, the materials in the area are normally affected by karstic processes that generate cavities and aquifers and which progressively cause the area to sink.

When this area is small, it is called a subsidence doline).</p><p><br></p></div>">doline, while large ones are referred to as poljes. The size of the Formentera lagoons suggests that these could be poljes, although further studies on this regard are needed.

In any case, once the land that is currently occupied by the lake collapses, it suffers both erosive and sedimentary processes.

During the Pleistocene period, and to date, dunes and beaches have been deposited and filled in the previously created basin. The oldest are fossilized, forming sand-sized clasts.</p><p><br></p></div>">sandstone, while the more recent dunes and beaches continue to be active and are not consolidated.

Both the fossilized sediments on the beaches and dunes and the current deposits that form the barrier t separate the lake from the sea except for a point in the north, where the marine currents have permitted a large quantity of fish to pass, hence its name (Fish Lake).