Image:Sudbury Crater.jpg

The Sudbury and Wanapitei craters in Ontario, Radar image

From NASA: The partially circular lake-filled structure on the right (east) is the 8 km (5 mi) wide Wanapitei crater, estimated to have formed 34 million years (m.y.) ago. The far larger Sudbury structure appears as a pronounced elliptical pattern, more strongly expressed by the low hills to the north. This huge impact crater, with its distinctive outline, was created about 1800 m.y. ago. Some scientists argue that it was at least 245 km (152 mi) across when it was circular. The strong northwestward thrusting of the Grenville Province terrain against the Superior Province (containing Sudbury) subsequently deformed it, more than 900 m.y. later, into its present elliptical shape (geologists will recognize this as a prime example of the "strain ellipsoid) model. After Sudbury was initially excavated, magmas from deep in the crust invaded the breccia filling, to emplace against its walls. Some investigators think that the resulting norite rocks are actually melted target rocks. This igneous rock is host to vast deposits of nickel and copper, making this impact structure a multi-billion dollar source of ore minerals.[1]

NASA's Remote Sensing Tutorial. Originally uploaded in english Wikipedia on 2004 Nov. 26by user:Kbh3rd

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NASA

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