Professor Francis Thackeray © 2001
Evolutionary Studies Institute (ESI), University of the Witwatersrand
PO WITS, Johannesburg 2050, South Africa

Robben Island was not always an island. Just as climate is changing today, so too did climate change in the past, often on a far greater scale than that which we see at the present time. Notably, when global climates were warmer than they are at present, much of the ice at the North and South Poles melted, causing sea levels to rise almost everywhere on earth. By contrast, when global changes were cooler or colder than they are today, much of the water in the world's oceans was trapped as ice at the poles, such that sea levels dropped.

It is now possible to obtain general estimates of how sea levels may have changed in Table Bay, adjacent Cape Town, and it is also possible to use this information together with present-day sea-depth data (bathymetric measurements) in Table Bay, to reconstruct changes in past environments within the past 15,000 years.

The results that have been obtained from a preliminary study show that about 10,000 years ago there was a land bridge between Robben Island and the African mainland. (One might call this landbridge a "Short Walk to Freedom"). This land bridge occurred because temperatures were cooler than they are today. 15,000 years ago, the polar ice caps were much more extensive than they are at the present time, such that the land which is today associated with "Robben Island" would instead have been a small hill (a "koppie") on an African landscape that stretched from the base of Table Mountain to a shoreline that extended further west from the present shoreline.

The series of images below suggest the kind of changes that can have occurred in Table Bay within the past 15,000 years. The images serve as a reminder that changes in sea level can occur as a result of global changes in temperature and ice-volume at the poles. If global warming continues to occur in the future, we may see a rise in sea level that affects human settlements on shorelines, world-wide.

Back to Top of Page

Return to INDEX