Scientists in Greenland have uncovered evidence for what may be the oldest impact crater ever found. And it would be hard to find one much older, because Greenland has some of the oldest exposed rock on earth. It’s also good it happened a long time ago — this impact was huge:
(MSNBC) — Researchers think the crater was formed 3 billion years ago, making it the oldest ever found, said Danish researcher Adam Garde. The impact crater currently measures about 62 miles (100 kilometers) from one side to another. But before it eroded, it was likely more than 310 miles (500 kilometers) wide, which would make it the biggest on Earth, Garde told OurAmazingPlanet.The team has calculated it was caused by a meteorite 19 miles (30 kilometers) wide — which, if it hit Earth today, would wipe out all higher life.
How bad would a 19 mile (30 km) wide object be if it hit today?
I assumed being 500 miles away while a 19 mile-wide object made of lighter rock or solid ice struck land at a 45 degree angle with a velocity of 20 miles per second. According to the Purdue University impact simulator, the fireball would be more than 1000 times brighter than the sun. A person caught in the open, clothes and hair would ignite, skin would suffer second and third degree burns. Just glancing at the fireball as it streaked across the sky or on the horizon would cook your retinas like tiny fried eggs.
Within a few minutes red hot ejecta will begin streaking in, some of it the size of bowling balls traveling at supersonic velocity, the material will accumulate up to an average depth of thirty feet. Well before that can happen the shock wave will arrive with such force it will destroy highway overpasses, parking garages, and steel-reinforced office buildings. Most wood frame and brick structures will be reduced to rubble. The crater will be about 150 to 200 miles or more across and initially so deep it could pierce the crust and touch the mantle, before it rebounds, flows, and stabilizes at a depth of a mile or two.
If it hit water the effects would be similar, except mega tsunamis, hundreds of feet tall in many places, would lash coastlines all over the world. If such an object landed a hundred miles east of Miami, the tsunami surge along the beaches would be so enormous they could wash completely over the entire tip of the Florida peninsula from east to west.
If you play around with impact simulators for hours, like I do, and it’s a lot of fun too, you’ll see this kind of impact is way worse than the K-T, by at least an order of magnitude or two. But I don’t think it would wipe out all higher life as the article suggests, not even close. The lethal surface effects would extend to roughly one thousand miles or more. Only people in a hardened underground shelter with several meters of solid bedrock or reinforced concrete above would escape instant or lingering death inside that circle, and only those with provisions prepared to wait out a year or more of famine, drought and strange weather would live more than a month or two after that. But this isn’t Armageddon, one of the worst sci-fi’s ever made, this is more like Larry Niven’s excellent disaster novel, Lucifer’s Hammer. Millions of people would survive, as would many animals and plants.
Wiping out most or all complex life would take something even worse, and it might look something like this.