Manitoba Geology—Precambrian

_{Courtesy Manitoba Geological Survey}

Beneath Manitoba's veneer of glacial sediments is the ancient continental basement, the North American craton. Ultimately, all continents are built of smaller pieces of crustal rocks, stuck together over the eons. A modern example of this is the state of Alaska, where plate tectonic motions have carried large areas of rocks—terranes—from southern lands onto the North American plate. In Canada, the Precambrian rocks shown here are deeply eroded, and most of their history is wiped out. They probably also represent terranes, but we cannot be as certain, hence the more neutral term "geological domains."

The Phanerozoic Eon includes all of Paleozoic, Mesozoic, and Cenozoic time, from about 550 million years ago to the present. Precambrian time includes the Proterozoic and Archean Eons, going from the Phanerozoic back to almost 4 billion years ago.

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