In the northern part of Quebec, among some of the oldest rocks on the continent, a curious ring of water surrounds a remarkably circular island. This is the site of Manicouagan crater; with a diameter of more than 70 km across its prominent rim (the outer shore of the lake), it is one of the largest and best exposed craters on the planet. Manicouagan was formed by a meteor’s collision with Earth more than 200 million years ago.
As a result of underground fluid pressure pushing the rock in the crater upward during a bout of post-impact equilibration, Manicouagan has a plateau in the center, rather than the characteristic depression associated with craters. The remaining, ring-shaped depression filled with water, creating the lakes Manicouagan and Mouchalagane.
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