Very Old Rocks

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Algonquin is classic "Canadian Shield" country - some of the oldest rocks on the North American content. The Algonquin highlands are a huge block of 1.5 billion year old rock. The Canadian Shield comes to the surface in a huge circle around Hudson Bay. However, the Shield rocks extend west to the Rockies, south-east to the Appalachians and as far south as Texas; however, they have been buried under deposited sediment around the Great Lakes and in the Great Plains area.

See Geologic Time(USGS) or Geological History (Nova Scotia)


About half a billion years ago, a meteor slammed into the north end of the park. It made a hole 4 kilometers (2.5 miles) wide and 600m (2000 feet) deep, which is now called the Brent Crater. The road which goes in to this area travels along a glacial "esker", a sand and gravel ridge probably left behind by a river of meltwater flowing under a glacier, for the first 18 km (10 miles) or so; after that, it gets somewhat bumpy.

Crater Links

Reminders of the Arctic

About 11 thousand years ago, the last of the glaciers scraped through the area now occupied by the park. Arctic plants still remain in the Barron Canyon area in the northeastern part of the park. The Barron Canyon itself was formed by the massive outpouring of glacial meltwater from ancient Lake Algonquin.

Plumbing Problems?

Because the rock underlying the park doesn't drain very well, the park is dotted with rivers, lakes and spruce bogs which are often located in depressions gouged out by glaciers. With few exceptions, the lakes tend to be acidic because there are very few soluble rocks such as limestone within the park to balance acids from plant material or acid rain. In general, rivers and streams in the Canadian Shield do not tend to carry much sediment since these ancient rocks are very resistent to erosive forces.

East Versus West

The eastern third of Algonquin is lower than the western two-thirds: there is enough difference that

Virgin Forest - Hardly!

Most of the old-growth forest is gone from this area as a result of the area being opened up for logging in the 1800's. Even today, there is a controversial balance between wilderness, recreational use and managed forest.

More places in the Canadian Shield