By Dr David Whitehouse
BBC News Online science editor

An ancient supercontinent, far older than anything ever proposed before, has been pieced together by an international team of geologists.
The giant landmass, which has been dubbed Columbia, would have spread across the face of the Earth more than one and a half billion years ago.

The theory is that it then fragmented into smaller pieces before reassembling into another super continent called Rodinia; and, later still, a huge landmass scientists now refer to as Pangea.