Wafa Glacier, Greenland, Holocene discussed on Quirks and Quarks
We just happen to pass over high WAFA glacier on a regular basis. So over time we built up a record of measurements of the ice thickness. And from that, my Danish colleagues detected a conspicuous closed depression, which turned out to be an impact crater boy. So you saw this circular feature. How did you know that it was an impact crater? Well, we didn't know initially what we did know is that it was unusual. And once we notice the depression on the map, I went in and looked at the raw data, and what I could see was evidence of a an elevated rim around the edge. And then when you plotted those points, they fit a nice circle. So that was suggestive at the very least. But what it took for us to confirm? The finding was to do a more detailed airborne radar survey in may of two thousand sixteen and then in summer of two thousand sixteen my colleague Kirk care from the natural history museum in Denmark. He actually went. Two two high WAFA glacier and gone on the ground via helicopter, and collected geologic samples essentially bags of sand that we were able to analyze the lab and confirmed that there was impact material in them. So do you have any idea? How old is impact crater is. Well, that's the the key question that we have the Larry of the ice was extremely unusual. What we saw how glacier did not resemble. What we'd seen elsewhere in Greenland the larynx for during the Holocene epoch? So the last eleven thousand seven hundred years the period of relative warrants since the last ice age that leering was well behaved normal, but before that the lowering was much more complicated. And we saw folding we saw disturbed blaring. We saw debris and trained within the ice. And that suggested to us the outside possibility that the impact might be extremely maybe only slightly predating in the Holocene when we put all of our circumstantial evidence about the age together. What we concluded is that the crater self is unlikely to predate the Pleistocene era, which is last two point six million years when ice sheet of some form has existed in Greenland. So then you've got a range here from two million years two point six million years to twelve thousand years when it could have happened. Yes. So that's a pretty large range, of course..