The History of the Rocks

This chapter discusses a very general history of the formation and deformation of the rocks that form the walls of the Grand Canyon.

At the time this book was written, the term "Algonkian" was still being used to represent a period of time between the Archean and the Cambrian, despite the proposal (from at least 1908) to the Geological Society of America that the term "Proterozoic", which is used worldwide today, be used to identify this era of geological time. As far as I can tell, the term "Algonkian" was only ever used to describe rocks of this time in North America. You can download a pdf of the geological time scale from the Geological Society of America here. One should also note that today there are far more than the 12 divisions of geologic time mentioned in this book!