So I was meandering around in Google Maps looking up hiking trails in the Adirondacks, and stumbled on a really weird mountain formation in southeastern Quebec called “Mont Mégantic”. This led to a whole string of Wikipedia and geology site searches. I learned a bunch fascinating geological history I didn’t know about!

It turns out Mont Mégantic is home to an observatory, a bird sanctuary, and a bike race, but it was the shape that caught me. It looks like a big meteor crater?

In fact, it’s a volcanic mountain. If you zoom out on Google Maps, you’ll see that Mont Mégantic is not alone – it’s one of a series of odd circular mountains jutting up out of the StLawerence Lowlands, dotting a line Westward to Montreal as part of the Monteregian Mountain chain:

And eastward past the White Mountains, and on into the sea, forming the New England Seamounts:

So all of these little round hills are related! The chain of mountains (including Mont Royal) have been springing up (and are still being formed) over the past 200 million years as a super-hot hole in the earth’s mantle called “The New England Hotspot” slowly rolls along under the crust, melting it’s way through weak spots it finds.

Much more sexily, the hotspot is sometimes referred to as “The Great Meteor Hotspot” because it may have been formed by a meteor strike on the opposite side of the world – like a big crack in the opposite side of an egg.

So here’s where it gets really cool. If you take your finger on a map and drive it backwards along the line, you head northwest across a series of interesting geological landmarks: Mont Royal in Montreal, a handful of hills along the Ottawa river, and then further on the famous diamondiferous kimberlite mines at Temiscaming, the diamond mines in Kirkland Ontario, and then it stops. Apparently for millions of years this diamond-making ultra-hot magma plume struggled to melt through our ultra-hard Canadian Sheild to no effect.

But if you project where it ought to come out the other side, as some now very rich people at DeBeers did – it traces a path right over Attawapiskat diamond field in Nunavut. I bet there’s a lot of people right now trying to figure out where that line goes from there – because it will likely point to even more diamonds. We’re talking about reconstructing geological events that happened over 200+ million years ago, when the earth was a very different shape than it is now. As the arctic opens up to further mining development thanks to global warming, a fortunate side-effect will be a better understanding of very young earth geology.