Why are hot springs found in fractured areas of the Pyrenees?

Hot springs are found in the fractured areas of the Pyrenees as a direct result of the mountain range's complex geological history. During the process of mountain building, which involved the collision of the Iberian and European tectonic plates, the region's rigid granitic base was subjected to intense folding forces.1

While more plastic layers were able to fold without breaking, the rigid base fractured and became dislocated. These fractures created pathways that allowed groundwater to reach significant depths, where it was heated by the Earth's internal temperature gradient before rising back to the surface. Consequently, these breaks in the bedrock facilitated the emergence of hot springs, which are categorized as sulfurous when found within the axial massif and saline when located at the edges of the range.123