Day One

There are some places that as a geologist you want to go to. Today, I went to one of them. I couldn’t believe it when Kate revealed the challenge – go to a meteor impact site in Arizona, measure the size of the crater and estimate the size of the body that crashed into it. Immediately I knew we were talking about Meteor Crater – a feature whose image adorns almost every geology textbook and a classic example of how science works in mysterious ways. Geology undergraduates are brought up on how geologists argued for years about whether it was created by a volcanic explosion or an impact from space. A hundred years ago, the most respected geologist in the land had spent years carefully studying the problem, to conclude it was volcanic. A classic case of wrong answer for the right reason. Only in the last few decades did scientists come round to the idea that this really did come from outer space.

Poor Mike. Kathy and I have left him playing with marbles and sand while we fly off to Arizona. Jonathan and Ellen are happy enough – their common interest in astronomy is perfect for their task to measure the size of a crater on the moon, so they have their minds on higher things. Kate, obviously is coming with us to a small town in Arizona. Now there are a few things that Winslow in Arizona is famous for. (1) It was famed as one of the main stopping off points on the railroad and highway 61 heading west to California. (2) It has a dirty great hole in the ground a few miles out of town – more on that later. (3) Most importantly, there is a statue to The Eagles frontman, Don Henley, after immortalised the town with the words “Standing on the corner of Winslow, Arizona…” in that famous song. You can guess it. I can’t say it – I’ll end up just singing it constantly like we did when we got there.

Anyway, back to the business at hand. The crater is spectacular, particularly when you get to approach it from the air. We flew in by helicopter, skirting low over the flat desert floor until you rise up over the elevated rims of the crater and then see it’s full extent. I’d seen it hundreds of times in photos, but I still couldn’t believe how enormous it looks. And another thing, it wasn’t really circular – I was surprised how square it looked from some angles. Until now, I hadn’t given much thought to measuring it – I had been more preoccupied with ways of estimating the size of the lump that crashed into it. Besides, I was sure Kathy would think of something on the measurement side.

Some geologists that have spent decades studying the rocks in and around the crater for clues about what happened here. I had a day and a half. Thankfully, because the place is so famous I knew a lot of the clues that I needed to look for. First I knew that we didn’t have to bother looking for the meteorite in the bottom of the crater – it had vapourised on impact. Good news for us, but bad news for the guy who a century before had bought the crater to mine out the iron-nickel body he believed lay at its core. Still, you can see small dense metallic fragments littering the rim of the crater, though hunting for them is a popular tourist past-time. And the evidence for the enormity of the explosion that vapourised it is all around – powdered rock and enormous boulders occur all around the outer edges of the crater walls. It must have been some bang. Still, there was nothing that could give a definite answer to the size of the body that struck, and we still had to measure the blasted thing.

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