The island is the top of a massive submerged shield volcano that rises about 6 km (3.7 mi) from the floor of the Atlantic Ocean.

The most recent volcanic eruptions were on the west-central part of the island only 6,500 years ago, creating more cinder cones and lava flows.

At the end of this eruptive phase, an island circled by reefs was formed, its marine vestiges are evident in a calcareous layer in the area of Lameiros, in São Vicente (which was later explored for calcium oxide production).

Sea cliffs, such as Cabo Girão, valleys and ravines extend from this central spine, making the interior generally inaccessible.

[4] Daily life is concentrated in the many villages at the mouths of the ravines, through which the heavy rains of autumn and winter usually travel to the sea.