The Manicougan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 60 percent of all species. Though the crater has mostly eroded, Lake Manicougan outlines what is left of the 43-mile wide impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a reservoir and popular salmon fishing location.