Rising and falling sea levels over the last 700 000 years changed the shape of the outcrop and 12 000 years ago the sea level rose and created a channel between the Island and the mainland. The sediments that form the current base rocks of Table Bay and Robben Island were laid down approximately 900-800 million years ago where an ancient river delta entered shallow coastal waters. Evidence of this process can be seen by the ripple marks on the base of the oldest quarry in the south of the Island. This bedrock is now known as the Tygerberg Formation of the Malmesbury Group.
About 9 to 6 million years ago, rising sea levels led to the formation of beach terraces on the Island, through the deposition of shells and boulders. Another rise in the sea levels 3 to 4 million years ago resulted in additional terracing. The cementing of dunes formed sandy limestone and calcrete deposits about 2 million-10 000 years ago. The partially consolidated coastal dunes were created by strong winds during times of lowered sea levels.
