Eagle Butte Crater hard to see but full of wonder
About 35 km southeast of Medicine Hat you will come to a strange landscape seemingly unconnected the Cypress Hills to the east or the prairie expanse to the west.
You might not be able to put your finger on why it seems so strange, but you will know something odd is going on. The area looks like a slight, disc-like bowl in the midst of the landscape, but the bowl has no clearly defined edge. You can only pick up a trace of it here and there as you drive along Eagle Butte Road.
It might not be obvious to the casual observer but this area marks the site of an ancient meteor or comet strike estimated to have occurred sometime in the Paleogene Period (23-65 million years ago). The site is formally called the Eagle Butte Crater, and is the second largest impact crater ever discovered in Alberta.
“On the surface one doesn’t see too much,” says Alan Hildebrand, a planetary scientist from the U of C who has examined the crater in the past. “There is a hill where the central uplift is. The crater is 14 km in diameter. About 2 km of rock has eroded off that crater since it was formed; so we are really looking at the roots of a crater.”
The crater is hard to date more specifically because of its heavily eroded state, but Hildebrand says the crater is exciting to research anyway.
“It’s fun to explore in the sense that you could walk out into a field and find shatter cones. There is only one other crater in Alberta where you can see these deformed rocks and some other (impact) effects at the surface. Most of the known craters are buried. Eagle Butte Crater is unusual in that respect.”
Shatter-cones are deformed stones thrown up by a massive explosion or impact embedding themselves in the surrounding landscape.
Hildebrand estimates the size of the body, either meteor or comet, that struck the Eagle Butte area would have been about half a kilometre in diameter. Whatever it was, it struck with a force a half-million times more than the Hiroshima bomb.
According to Hildebrand, It would have been devastating to the plant and animal populations living in the area at the time. If it had hit today, he says, the shockwave alone would have probably spread far enough to wipe out Medicine Hat and most of its surrounding communities.
“You would not have wanted to be anywhere near that crater when it formed,” he states matter-of-factly. “It would have been forests at the time with some early birds and mammals inhabiting them. When the comet or meteor hit the ground a shockwave started going through the ground. That shockwave is initially powerful enough to vaporize the rock ... If you had been able to survive the shockwave, which of course you couldn’t, you still would have been buried by the ejecta. That ejecta layer would have been continuous to something like 30 km from the centre of the crater.”