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Manicouagan Impact Structure Quebec
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Manicouagan Impact Structure, Quebec

April 2, 2003
The large annular lake in this image represents the remnants of one of the largest impact craters still preserved on the surface of the Earth. Lake Manicouagan in northern Quebec, Canada, surrounds the central uplift of the impact structure, which is about 70 kilometers in diameter and is composed of impact-brecciated rock. Glaciation and other erosional processes have reduced the extent of the crater, with the original diameter estimated at about 100 kilometers. The impact that formed Manicouagan is thought to have occurred about 212 million years ago, toward the end of the Triassic period. Some scientists believe that this impact may have been responsible for a mass extinction associated with the loss of roughly 60% of all species.