structural:expansion, quality:corruption
Coastline

The coastline of the Iberian Peninsula is 3,313 km (2,059 mi), 1,660 km (1,030 mi) on the Mediterranean side and 1,653 km (1,027 mi) on the Atlantic side. The coast has been inundated over time, with sea levels having risen from a minimum of 115–120 m (377–394 ft) lower than today at the Last Glacial Maximum (LGM) to its current level at 4,000 years BP. The coastal shelf created by sedimentation during that time remains below the surface; however, it was never very extensive on the Atlantic side, as the continental shelf drops rather steeply into the depths. An estimated 700 km (430 mi) length of Atlantic shelf is only 10–65 km (6.2–40.4 mi) wide. At the 500 m (1,600 ft) isobath, on the edge, the shelf drops off to 1,000 m (3,300 ft).

The submarine topography of the coastal waters of the Iberian Peninsula has been studied extensively in the process of drilling for oil. Ultimately, the shelf drops into the Bay of Biscay on the north (an abyss), the Iberian abyssal plain at 4,800 m (15,700 ft) on the west, and Tagus abyssal plain to the south. In the north, between the continental shelf and the abyss, is an extension called the Galicia Bank, a plateau that also contains the Porto, Vigo, and Vasco da Gama seamounts, which form the Galicia interior basin. The southern border of these features is marked by Nazaré Canyon, which splits the continental shelf and leads directly into the abyss.