Origin
During the Triassic period -beginning about 251 million years ago and ending about 200 million years ago-, at a time when all the continents were united forming the continent called Pangea, Salinas de Añana was submerged under a great ocean. The evaporation of its waters caused the deposition of large layers of evaporites at the bottom which, over time, were covered by other strata.
The existence of salt in Añana is explained by the geological phenomenon called diapir. In general terms it consists of the ascension towards the terrestrial surface of older materials due to its lower density, in the same way that an air bubble immersed in a liquid has an ascending movement.
This particular process began some 220 million years ago, when the evaporitic rocks of the Triassic in Keuper facies -located at a depth of about 5 kilometers- began to rise to the surface, dragging with them the materials that characterize the salt landscape: carniolas, ophiolites, limestones, marls, clays, etc. This process is still active.
Rainwater falling on the diapir first passes through the upper rock strata and then through the salt layers, returning to the surface in the form of springs or hypersaline upwellings. The springs of Añana provide an average flow of about 2 liters per second, with a salt concentration of about 240 grams per liter.
The hydrological system related to the diapir is completed with the Arreo Lake, whose waters, due to its location in a closed basin on evaporation, are also saline. Both the lake and the salt flats contain deposits with important paleoenvironmental and paleoclimatic information, as well as a biodiversity typical of saline environments. For this reason, and in order to preserve them, both areas have been included in the RAMSAR List of Wetlands of International Importance.
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