The Carcavai Fault extends over 20 km of the emerged territory between S. Brás de Alportel and Quarteira with a general NE-SW direction, extending into the immersed territory of the continental shelf.

This geological structure accommodates the Cadoiço river from Loulé to the coast.

The Cadoiço river belongs to the Carcavai river basin and originates northeast of the city of Loulé, at the foot of the Cabeça Gorda hill. A section of the Cadoiço river crosses the city of Loulé in an underground tunnel, its waters re-emerge in a spectacular way in a waterfall located a few meters upstream from Fonte do Cadoiço, a water spring that flows from a rocky cavity made of limestone tuffs.