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At the bottom of the sea 600 million years ago. 600 million years ago the materials of Malpica-Tui unit (UMT) were situated at the bottom of the sea between two big continents, Gondwana and Laurasia. It was the beginning of the Varisca orogeny, Modificado de Diez Fernández, R. Evolución estructural y cinemática de una corteza continental subducida: la unidad de Malpica-Tui. 2010. Salamanca as it was named. During this period the materials of Gondwana were accumulated on the ocean to form sedimentary rocks. During Varisca orogeny, these stones suffered changes of pressure and temperature, that is to say, suffered metamorphism. On the beach of Aviño we can see the footprints of this process on the materials. Beo´s rock doesn´t show the effects of a pressure and temperature increase. Two images of shale, a type of metamorphic rock, from Aviño´s beach. Schist are formed when they undergo a significant pressure and temperature increase. Both are gneiss, metamorphic rocks formed by a pressure increase and temperature close to melting. Right. Gneiss of Ponteceso. Made from a sedimentary rock. Left. Gneiss of Barizo. Made from an igneous rock.