La Crosa volcano, also called “La Crosa de Sant Dalmai”, shares the space between the Catalan municipality of Vilobí d’Onyar (in the lands of Sant Dalmai) and those of Bescanó and Aiguaviva. Located in the NE of Catalonia, in Girona.
It is a wide volcanic maar or crater (over 1.200 m, one of the largest in Europe) and low altitude (156 meters above sea level) formed by a phreatomagmatic eruption, produced by an explosion caused by groundwater in contact with ascending magma from the main chamber. The violent explosions have formed a ring of pyroclastic projections, formed both by juvenile materials (of basaltic composition, chalk, tuff and some volcanic bombs) and by fragments of subterranean rocks (igneous and metamorphic fragments). The phreatomagmatic origin of the Crosa maar differentiates it from the rest of the volcanoes in the area, in which strombolian eruptions predominate. It must be said, however, that within this phreatomagmatic volcano we find a smaller cone of the Strombolian type.
The eruptive period of La Crosa is between 7.9 and 1.7 million years (My), characteristic of the volcanic processes of the La Selva depression. The oldest in the Empordà region date from 12 to 8 My and the most recent, from La Garrotxa, are between 500,000 and 10,000 years old.
Figure 1. View of La Crosa de Sant Dalmai volcano, from the Can Guilloteres viewpoint.
