Geomorphology and thermal regime of Peña Ubiña Massif (Cantabrian Mountains)
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Abstract
Peña Ubiña Massif is one of the highest mountain areas in the Cantabrian Mountains (El Fontán sur, 2417 meters a.s.l.). Due to its vertical orography, it retains the moisture carried by the winds, causing abundant fog and rainfall that exceeds 2000 mm on its summits, many of which are in the form of snow. Karstic, fluviotorrential, glacial, periglacial and gravitational processes and landforms have been identified (relict in some cases and active in others). The action of the karst led to the development of erosive landforms such as dolines, nivokarstic sinkholes, chasms and a great diversity of karren. On the other hand, Peña Ubiña Massif presents a well-developed glacial landscape composed by erosive landforms such as glacial troughs, roches moutonnées and glaciokarst depressions (the latter of mixed genesis, karstic first and glacial later); as well as accumulation landforms, especially several generations of lateral, frontal and basal moraines, which allowed the identification of three main glacial stages (Maximum Ice Expansion Stage or MEH; Internal Stage I and II and Altitude Stage I and II), with 20 glaciers which occupied an extension of 5004 hectares during the MEH Stage. For its part, the present-day thermal regime is characterized by an abundance of frosts, but by a reduced number of freeze-thaw days on the soil. These cold conditions favour the development of cryoturbation, frost shattering, solifluction, rapid mass movements such as debris flows and snow avalanches, and an abundance of snow, which tends to remain between 6-8 months above 1800 meters a.s.l.