 The volcanoes have erupted basanite.The main components of the rocks at La Breña-El Jagüey are clinopyroxene, ilmenite, olivine, plagioclase and titanomagnetite, with rocks sporting variable textures.The participation of water in the formation process of these magmas is debatable; the rocks may have been influenced by sediments from the uppermost part of the subducting Farallon slab.