The vanished ocean at the heart of this book formed a little over 250 million years ago as the last supercontinent, Pangaea, slowly assembled. At that moment, nearly all the Earth’s landmasses were united in a single unit consisting of two halves – Gondwanaland in the southern hemisphere and Laurasia in the northern – stretching almost pole to pole and joined by an isthmus in the west. 

The Earth from space came to resemble a giant copyright mark, ©, with the bi-lobed supercontinent enclosing a huge embayment of Panthalassa, the global ocean. This was the Tethys – perhaps the most prodigious sea the Earth has ever produced. Born amid the worst mass extinction in history,