Sudbury Basin

The Sudbury Basin Also known as 'Sudbury Structure' or the 'Sudbury Nickel Irruptive' is a major geologic structure in Ontario, Canada. It is the second-largest verified impact crater on Earth, as well as one of the oldest.Verified: means we know it was an impact crater 

The basin is on the Canadian Shield in the city of Greater Sudbury, Ontario. The Sudbury Basin is referred to locally as "The Valley". The urban core of the former city of Sudbury lies on the southern outskirts of the basin.

The Sudbury Basin is near a number of other geological structures. None of the structures are directly related to each other in the sense of coming from the same geophysical processes.

Formation
The Sudbury basin was formed by a strike from a bolide about  in diameter. It occurred 1.849 billion years ago in the Palaeoproterozoic era.Davis D. 2008. Sub-million-year age resolution of Precambrian igneous events by thermal extraction-thermal ionization mass spectrometer Pb dating of zircon: Application to crystallization of the Sudbury impact melt sheet. Geology.

Debris from the impact was scattered over an area of  and traveled over  away — rock fragments ejected by the impact have been found as far as Minnesota.Associated Press: "Ontario crater debris found in Minn." Star Tribune, July 15, 2007

With such a large impact, debris was most likely scattered globally,Melosh J. 1989. Impact cratering: a geologic process. Oxford University Press. but has since been worn away. Its present size is believed to be a smaller portion of a  round crater that the bolide originally created.

Subsequent geological processes have deformed the crater into the current smaller oval shape. Sudbury Basin would then be the second-largest crater on Earth, after the  Vredefort crater in South Africa, and larger than the  Chicxulub crater in Yucatán, Mexico.

Structure

The full extent of the Sudbury Basin is  long,  wide and  deep, although the modern ground surface is much shallower.

 References 

Category:Geography of Ontario
Category:Impact craters