The Shield by WB Skinner, who shot this photo near dark close to Thunder Bay, Ontario at a section of the Current River known simply as the Cascades.
WB Skinner writes:
The Canadian Shield, also known as the Precambrian Shield or Laurentian Plateau, covers about half of Canada as well as most of Greenland and part of the northern United States; an area of 4.4 million square kilometers (1.7 million square miles).
It is the oldest part of the North American crustal plate and contains fossils of bacteria and algae over 2 billion years old.
The shield is composed of granite and the earth’s greatest area of exposed Precambrian rock (igneous and metamorphic rock formed in the Precambrian geological era 500 million years ago).
The shield was the first part of the continent to be permanently raised above sea-level. Subsequent rising and falling, folding, erosion and continental ice sheets have created its present topography. The reoccurring invasion and withdrawal of the ice sheets (1.6 million to 10,000 years ago) depressed the surface creating Hudson Bay, scraped out tens of thousands of lake basins, carried away much of the soil cover and redeposited glacial debris.
via Dave Pollard