he Sudbury basin formed as an impact from a bolide approximately 10–15 km (6.2–9.3 mi) in diameter that occurred 1.849 billion years ago[2] in the Paleoproterozoic era.
Image taken from Space Shuttle Challenger in 1984/1985
Debris from the impact was scattered over an area of 1,600,000 km2 (620,000 sq mi) and traveled over 800 km (500 mi) away — rock fragments ejected by the impact have been found as far as Minnesota.[3]
Models suggest that for such a large impact, debris was most likely scattered globally,[4] but has since been eroded away. Its present size is believed to be a smaller portion of a 250 km (160 mi) round crater that the bolide originally created.
Subsequent geological processes have deformed the crater into the current smaller oval shape. Sudbury Basin is the second-largest crater on Earth, after the 300 km (190 mi) Vredefort crater in South Africa, and larger than the 180 km (110 mi) Chicxulub crater in Yucatán, Mexico.