Jens Keukeleire outpowered a peloton depleted by the hills of a long 193.2-km ride to Bilbao to hand his Orica-BikeExchange team their second stage victory in the Vuelta on Thursday. The 27-year-old Belgian surged in the final stretch to outsprint France's Maxime Bouet (Etixx-Quick Step) and consistent Italian Fabio Felline (Trek-Segafredo) to the line on a day when the leading favourites had declared a ceasefire. Colombia's Nairo Quintana retained his red jersey.
The stage in videos
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The stage in pictures
Alejandro Valverde and Nairo Quintana (Movistar) during stage 12 of the 2016 Vuelta a España © J.A. Miguélez
Between headlands, rocky areas and poljes
The faults and the dissolution of rocks give way to a particularly fractured topography. The stage is scattered with karst formations (sinkholes, channels, stalagmites, galleries, etc.). The Puente Viesgo Wellness Spa is another notable example of the importance of geology, because a detailed study of the region's faults and karst formations is what allows these thermal centres to flourish and make the most of the mineral and medicinal waters.
Between Penagos and Pamanes, we head to the foot of Peña Cabarga, very close to the Karst de Cabárceno, a nature park that offers strange landscapes. A large part of its interest lies in the fact that is has a mix of different natural (karst) topographies and mining footprints.
We then climb the Alisas mountain pass, passing through the Natural Park of the “Collados de Ansón”. It is a limestone massif whose most characteristic traits are the reliefs formed by the ancient glaciers that once covered this region thousands of years ago. In this area, glaciers formed at the lowest levels recorded within the Iberian Peninsula, as shown by the Bustalveinte moraine, located less than 600 metres high. A large part of this mountain pass still preserves some impressive limestone headlands dating back 100 million years.
A few kilometres north of Arredondo, is the poljé of Matienzo, included in the Spanish Inventory of Geologic Singular Sites (IELIG). It is a depression over a kilometre wide, with a flat surface, that formed a long time ago when several caves collapsed. The poljes' springs often lead to these being inundated when the underground waters rise, resulting in a flat surface that is full of sediments.
Past Gigaja (km 75 of the stage), the road passes of the Coluviones de Carranza, included in the IELIG. This is a large accumulation of materials that have broken off and fallen from the rock walls. Many accumulations such as this one form due to the ice that penetrates the rocks and breaks them, much like when you forget to take a bottle out of the freezer.
The wealth of the area's Geological Heritage is truly unique. Just as you enter the Basque Country, before reaching Karantza/Carranza, we pass right near one of the greatest concentrations of Geological Interest Locations (IELIG) in Spain. Less than a kilometre north of the road (km 78 of the stage) we have five of these unique spots. Three of them are ancient mines, the Torca del Carlista is a great karst system, and the Cueva de Pozalagua can, paradoxically, be seen from the sky. In fact, it features an amphitheatre carved into the rock, using the ancient mine, which is a good example of how to take advantage of Geo-diversity.
Karst. Name given to a group of processes and reliefs related with the dissolution and precipitation of rocks formed by soluble minerals, such as calcite or gypsum.
Polje. A depression formed by the collapse or dissolution of limestone rocks, such as a sinkhole, but characterised by the fact that it often becomes inundated when the groundwater level rises through the springs, called “ponors”. These are mild inundations that make the earth richer and rarely cause any other problems.
Jersey wearers after the stage 21
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