It covers two distinct geological features of the North Atlantic Ocean: the Barra Fan and the Hebrides Terrace Seamount.

The fan lies to the east of the Hebrides Terrace Seamount, in a region known as the Hebridean Slope, where the seabed drops from the continental shelf, at a depth of c. 150 m below sea level, down to Rockall Trough (c. 2300 m below sea level).

[2] The seamount of the Hebrides Terrace is thought to represent the remnant of an ancient volcano that rises to a height of almost 1 km above the surrounding seabed.

It lies to the west of the Barra Fan, and supports a diverse range of marine life, including cold-water corals and deep sea sponges.

[3] The seamount is the location of a positive gravity anomaly that is thought to indicate the presence of an igneous body of rock some 17 km thick.