The average sea level during the Last Glacial Maximum,  20,000 years ago, was 120 meters lower than today. The continental shelf, which today lies beneath the waters of the Atlantic Ocean, was then emerged, and what we call today the shelf's edge corresponded to the coastline during this recent cold climatic period.

In the same way that today river valleys and faults can be seen carving out the profile of the coast, geophysical studies on the Algarve shelf in the Algarve territory have identified a paleovalley, nowadays filled with sediments, crossing the platform and incising the edge and the slope, in alignment with the São Marcos-Quarteira fault.