The second largest impact crater isn't as obvious, but the Sudbury Impact Basin is huge and a great source of nickel.

Wikipedia: The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is the second largest known impact crater or astrobleme on Earth, and a major geologic structure in Ontario, Canada.

cheers,

Actually, exploring craters on this planet is fascinating!! Erosion has cross-sectioned many of them and study of the various stages of the cratering process is possible.

http://ottawa-rasc.ca/wiki/index.php?title=Odale-Articles

Chuck

Scarily, looking at all these images and their various dates of impact is the message is -its only a matter of time…..

True, but consider this. We may only be a few decades away from being able to avert all catastrophic asteroid/cometary collisions with Earth. In just 100 years we've gone from finding a handful to tracking the orbits of hundreds of thousands of these things, so it's already getting pretty difficult for one of them to sneak up on us without our noticing.

Assuming even a modest improvement in detection and spacecraft technology, Earth will soon be pretty much safe from all but the most unlikely collision scenarios, quite possibly in the lifetime of any teenagers reading this website.

Now, closer to home, there are a number of much scarier catastrophes awaiting us that we can do nothing about and may never be able to avert. One day the southern flank of Kilauea, the big island in Hawaii will give way (it has done so before) and a tsunami, perhaps 50-100ft high will spread out across the ocean and devastate the Pacific Rim. Those on the Eastern Seaboard of the US are not safe either since a similar fate lies in wait when one of the flanks of the volcanic Canary Islands slump into the sea.

Live safely in the middle of the USA? Think again! The caldera volcano under Yellowstone is just waiting to blow its top one day, making Mount St. Helens and Mt. Etna look like fire crackers. it will drown a large portion of the continental US in feet of ash when it finally blows its top, which it certainly will one day.

Thankfully, none of these is likely any time soon (i.e, within the next few hundred years), but they are far more difficult to prevent than an asteroid falling from the sky.

"When it hit, the asteroid or comet "fractured the crystalline bedrock below to at least a depth of 7 miles (11 kilometers) and a width of 85 miles (137 kilometers). "

http://news.nationalgeographic.com/news/2001/11/1113_chesapeakcrater.html

I actually "discovered" the Manicouagan Reservoir crater and the Clearwater craters whilst zooming around in Google Earth. OK – so not actually discovered – but they were unknown to me until I saw them and recognised their shape as being obvious impact craters.

I don't know where it would come in the pecking order but there is also a recently discovered impact crater off the UK coast – known as the "silver pit". This BBC news article gives the detail:
http://news.bbc.co.uk/1/hi/sci/tech/4360815.stm

Scarily, looking at all these images and their various dates of impact is the message is -its only a matter of time…..

Here's hoping that current research into fending off asteroid impacts goes well.

Made me wonder what a direct hit on a mountain range would look like. It would probably take a top off a mountain, which would make a glancing blow pretty interesting. I'm sure you wouldn't want to be standing further down the valleys leading down from the range. Just fun for thought.