Local: Sudbury History - The Canadian Shield
The rocks that form the Canadian Shield were formed about four billion
years ago during the Archeon Eon of the Precambrian Era. Erosion of
this extremely rugged, mountainous landscape deposited enormous
quantities of clays, silts, sands and gravels into the surrounding
waters. Compressed by their sheer cumulative weight and the heat of the
shifting Earth's crust, sedimentary and metamorphic rocks formed during
the Proterozoic Eon of the Precambrian Era.
A significant event ocurred when a large crater was formed. Two
theories exist on the origin of the crater: the first is that a meteor
slammed into the region; the second that it is the result of a huge
volcanic explosion. The movement of the Proterozoic rocks northward
along the Grenville Front compressed the crater into the present day
oval shape. The Sudbury basin is the richest deposit of nickel ore in
the world.
More recent rocks that were formed above these ancient layers have since
been largely removed by the scouring action of glaciers that covered
northern North America in the several ice ages in the past
100,000 years.
The last ice age scraped the rocks in a NNE (north-north-east) to SSE
(south-south-east) direction. At the end of the last ice age, all the
waters in the Sudbury area (and the great lakes) drained to the east,
toward the Ottawa River. After the weight of the glaciers left this
area, the land slowly began to rise. The surface rose about 20 metres at
the eastern end of Lake Nipissing, and the French River began flowing to
the west into Georgian Bay. The soil on which trees and other vegetation
grow in this part of the continent are the result of gradual sediment
buildup since the last ice age.
More history of Sudbury
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