So, there is an overwhelming prevalence of acid rocks (granites and schists), a little representation of basic and ultrabasic rocks, and a minimum quantity of limestone rocks in Galicia. However, this apparent simplicity was modified when the African plates gave rise to Alpine tectonics and broke the Iberian Northwest old Massifs into one thousand blocks, with their own and singular dynamics. Without them, Galician landscape would be flat and worn away by erosion of hundreds of millions of years, and not having the appearance of young fluvial valleys.
Historia Natural. Geología