In December of last year Science News reported on the discovery of a crater under the ice in Greenland. It is thought to have been caused by a meteorite nearly a mile wide. It was discovered during a scan of the thickness of the ice in the polar regions. The researchers were drawn to look more closely at the area due to the rounded edge of the ice over the crater.
In 2001 I was taking a commercial flight from California to the east coast. As I often do I took out the airline magazine from the seat back pocket and looked at the map of all the airline’s routes. As my trip took me via Dallas, I realized that the route would take us over Winslow, Arizona. This meant we might be flying over America’s most accessible meteor crater. I asked the flight attendant if she would ask the pilot to let us know if the crater could be seen from the airplane. About half an hour later the pilot announced that if we were to look out the windows on the right side of the plane we could see the crater.
There far below us with a clearly raised edge was an obvious crater in the Arizona desert. It was by no means tiny even at our perspective from thirty-some thousand feet. It was roundish, with a particularly squared-off shape. You could clearly see that it was a depression in the Earth.
Years before I had been there to see the crater, and had taken the opportunity to walk down to the crater’s floor. In 1971 I was driving to California for a stint in the Navy. My route west took me along I-40 which passes the Meteor Crater. I needed a break from the highway, and I was curious about what the crater looked like. It was summer, and it was hot. When I entered the visitors’ center and was purchasing a ticket the man at the counter asked if I was in the military and when I showed him my military ID card he waved me on through. I asked him if I could hike down into the crater. He said that if I wanted to I would have to hurry because it was at least an hour’s hike down and back. As I walked towards the door to the outside he called out to me, “Take plenty of water. And look out for snakes.” Good advice to a down-east boy on his first trip to the desert. The path was over a quarter mile long and rocky and steep. When I finally reached the bottom, I stood on the crater floor and looked up at the rim towering 500 feet above me. It had been windy and hot when I stood on the rim. On the crater floor there was no wind, and it was hotter. I don’t remember as much of the hike down into the crater as much as I remember the hike back out. I didn’t see any snakes, but I kept thinking that I should have carried more water. The path up was a scramble in the loose sand and rocks that easily gave way under my feet. When I reached the rim, I was hot, tired, and thirsty.
But it was a good hike – if only that I could say that I had done it. It’s not something they allow visitors to do anymore and probably with good reason. The crater can be a trap. It was simple to get down into it, but not so easy to get out of.
At over a half mile wide the Arizona crater is impressive in size but it doesn’t even crack the top ten of known impact craters on the surface of the earth. But most of the known craters are not as visible or accessible as the one in Arizona. They are hidden by millennia of erosion or they may be under water. The largest known impact crater is Vredefort crater in South Africa. It is 118 miles across and was created by an impacting celestial body that was approximately 3 to 6 miles across approximately 2 billion years ago. This crater is more than twice the size of the Chicxulub crater which is theorized to have been the finishing blow to the reign of the dinosaurs 66 million years ago. The recently discovered but undated crater under the Greenland ice sheet is 19 miles wide. Another crater in Greenland reported in 2012 in Space.com is estimated to be three billion years old and the oldest known impact site on Earth.
But back to Arizona. In the early 1900’s attempts were made to find the meteorite that crashed in to what is now the Painted Desert of Arizona. The object is estimated to have been up to 300,000 tons. The mass of the meteor and its speed likely caused the meteor to vaporize in its explosive impact. When you are on the rim of the crater its not hard to look up and imagine what the object might have looked like as it streaked across the sky and then exploded just before impact, carving out the crater. Soil and plants and rocks and rubble were heaved upward and outwards.
In 1994 I was again standing on the rim of the Arizona crater. I could look up and imagine the bright light that suddenly appeared in the sky and with a thunderous roar exploded in front of me. Of course if I had been standing there 50,000-some years ago I would have been vaporized as well. What is a safe distance from such a blast? Miles and miles I am sure. And even if I was at such a distance to only feel the earth tremble and to see the blinding flash on the horizon and to have been knocked to my knees by the pressure wave from the explosion, I am sure that it would have left a searing mark on my memory. The mark I carry now is one of looking up from the crater floor towards the rim and realizing that the best path for me to take was upward and out before the night fell. And I was wishing I had brought more water.
Information on the craters mentioned above may be found at:
Regarding the Vredefort site, https://geology.com/articles/vredefort-dome.shtml
The recently found crater in Greenland was reported in the December 8, 2018 Science News, https://www.sciencenews.org/article/impact-crater-greenland-asteroid-younger-dryas
In 2012 Space.com reported on what is the oldest known impact site on Earth, https://www.space.com/16366-oldest-meteorite-crater-earth-found.html
The home page of the Arizona Meteor Crater is https://www.meteorcrater.com/