Manicouagan

The Manicouagan Crater was formed when an asteroid struck the Earth approximately 215.5 million years ago during the Triassic period. The impact was so massive that it created a crater that is now one of the oldest and largest known impact structures on the planet. It is located in the Côte-Nord region of Quebec, Canada.

The distinctive ring shape of the Manicouagan Crater is caused by the Manicouagan Reservoir, a massive hydroelectric lake created in the 1960s by the Daniel-Johnson Dam. The dam flooded the crater's center, leaving the raised impact rim exposed as an island. The inner ring is actually the eroded root of the central uplift peak.

The original crater rim measured roughly 100 kilometers (62 miles) in diameter, though glacial erosion has altered its size over millions of years. Today, the visible outer ring of the reservoir measures about 70 kilometers across. This immense size makes it easily visible to astronauts orbiting the Earth.

Initially, scientists theorized that the Manicouagan impact might have caused a minor mass extinction event at the end of the Triassic period. However, recent dating of the crater shows the impact occurred about 10 to 12 million years *before* that extinction event. Therefore, the asteroid impact did not cause the Triassic-Jurassic mass extinction.