It is a volcanic plug and over 100 m high. It is part of the Firth of Forth Islands SPA, a Special Protection Area covering some, but not all of the islands in the inner and outer Firth. Bass Rock itself is an SSSI, a Site of Special Scientific Interest, in its own right.
It plays host to the largest gannet (Sula bassana or Morus bassanus) population on the east coast of the United Kingdom. The scientific name bassana or bassanus refers to Bass Rock.