The Sudbury impact
One of the largest impacts Earth has survived
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The Sudbury Basin in Ontario is the scar of an asteroid impact 1.85 billion years ago, today an oval depression some sixty kilometres long. The Sudbury structure is the second-largest confirmed impact structure on Earth and the best exposed, because later mountain-building tilted it on edge and laid open a cross-section through the entire melt sheet. It was long read as volcanic; shocked quartz and shatter cones settled the question in the 1960s. Nickel from here supplied a substantial share of world production through the twentieth century.
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An asteroid some ten kilometres across struck where Ontario lies today. The crater was originally over two hundred kilometres wide. Molten rock from the impact carried nickel and copper towards the surface, and those metals are why a mining town stands there now.
Sources
- French, Traces of Catastrophe (Lunar and Planetary Institute, 1998)
- Ontario Geological Survey: Sudbury Igneous Complex
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