minutes later supersonic monster boulders make secondary impacts from the ejecta of the original crater. The speed of sound is about 1000 kph or 650 mph (1000 ft per second, about 11 miles per minute). The ejecta flew 300 miles and if it was at the speed of sound or some multiple, it arrived minutes later but less than 30 minutes later.

Estimated Sudbury impactor size: 7 to 10 miles in diameter of lots of heavy nickel. That's like a half dozen Mount Everests in one hypersonic (say Mach 20 to Mach 100) impact. Momentum (kinetic energy) p = mv² which is mass times velocity squared. A car hitting a wall at 65 mph (100 kph) has some energy p. When the speed is Mach 20 which is about 2 km per sec or 7000 kph, the energy is 70 x 70 or about 5000 times as much. Mach 100 would be 5 x 5 x 5000 or 125,000 times as much.

Thank you for posting.

He was also a Professor Emeritus and was as passionate about his research. Dad always said he would do the same work even if he didn’t get paid for it. Another trait he shared was the ability to explain the science to folks with no background in the subject and make it interesting to them.

my cousins + i followed him in the woods to find it. then he suggested a short cut + we wandered all the way to a wilderness area. we got back to his car after quite a hike + got back hours later. but then wi also had glaciers.

And in addition to this cool account of geology in the region, I now know that Alexis Dahl has produced a number of very informative videos about cool stuff in the state of Michigan. Down the rabbit hole I shall happily go!

I’m a little disappointed that when I visited the Sudbury area many years ago, I missed the giant nickel!