Map 3. Plate Migration
Early Cambrian 543 Million Years Ago (Ma BP)
It would seem that the Mantle convection currents that had created Gondwana and moved it southwards were now reversing, such that the plate stopped moving, whilst Laurentia, Baltica, and Siberia continued their northward journey back up the western hemisphere, rotating anti-clockwise all the while.
Avalonia was still attached to the coastal fringe of Gondwana, trapping the Florida plate between South America and Africa. Gondwana covered the South Pole and spread up over the eastern hemisphere beyond the equator. What is now the Antarctic continent would then have been experiencing tropical conditions, as would parts of Siberia and Laurentia.
The widening Iapetus Ocean, the AEgir Sea and the Ran Sea were the 'birthplace' of the newly-evolving marine creatures with exoskeleton carapaces, such as trilobites, and shelled creatures, such as brachiopods and gastropods.
The planet's atmosphere increased in carbon dioxide levels throughout the Cambrian, and global temperatures increased accordingly. At this time no animals or plants lived on the land. Prior to the evolution of land plants, erosion rates would be extremely high, and the formation of anything resembling a modern topsoil would be impossible.
It is difficult for a modern person to imagine a temperate or tropical environment without vegetation or soil-forming organisms. Warm and very wet, without a single tree or shrub, and no grass to stabilise the inorganic sand and clay produced by weathering. The logical consequence of high erosion rates is high deposition rates in shallow continental shelf marine environments - ideal for fossilisation of the new life forms.