University of Bristol

The Cambrian environment

The latest Precambrian was a time of many changes. 800 million years ago a supercontinent dominated the earth, by the start of the Cambrian this was breaking up into smaller land masses, increasing the area of continental shelf environment and producing shallow seas.

Reconstruction of Early Cambrian continental positions.
From The Fossils of the Burgess Shale. Briggs D.E.G., et al, 1994.
Cambrian world

Photosynthesizers had reduced the amount of carbon dioxide in the atmosphere, causing the planet to cool down. Worldwide glaciations of Late Riphean and Early Vendian age occured between 800-600 million years ago, ending with the harshest ice-age in Earth's history. Oxygen levels were increasing for the same reason. After the glacial period, temperatures rose until by the time of the Cambrian itself the climate was warmer than it is today.

These environmental changes over the Cambrian/Precambrian boundary potentially are the driving forces behind the Cambrian explosion event, many theories have been put forward trying to link the two together (see Extrinsic causes)

On to: First appearances

timing triggers fossils controversies

This report was written by Abby Lane and was last updated on 20th January 1999