Monday, October 21, 2013

Top 10 Biggest Meteor Strikes In History

By Jeff Danelek

Our beloved blue planet gets pelted with debris from space all the time but, since most of it burns up or break apart in the atmosphere, it’s usually not a problem. Even when one does make it to the ground, they are rarely much larger than a small rock, minimizing the damage they’re capable of inflicting. Then, of course, there is that once-in-an-eon occasion where something very very large makes it through intact, and this can really do some damage. Fortunately, such hits are extremely rare, but they are worth noting, if only to serve as reminders of the power of the stars to undo the normal routine here on Earth, with little more than a few minutes’ warning. So where - and when - did these monsters hit? Let’s take a look at the geological records...

10. Barringer Crater, Arizona, USA
Already the home of the Grand Canyon, around 50,000 years ago Arizona decided to add yet another tourist attraction, when a 160-foot diameter meteorite landed in the northern desert, leaving an impact crater nearly a mile wide and 600 feet deep. Scientists believe the meteorite that caused the crater was traveling at over 28,000 miles per hour when it struck, causing an explosion about 150 times more powerful than the Hiroshima atomic bomb. Some scientists initially rejected the idea that the crater was caused by a meteor when no meteorite was found, but the modern consensus is that the rock melted in the explosion, spreading a mist of molten nickel and iron across the surrounding landscape. Though at a mile across, the crater is not all that large, the lack of erosion makes it an especially impressive site. In fact, it’s one of the few meteor craters that actually looks like what it is, making it a first-class tourist attraction - precisely as the universe intended.

9. Lake Bosumtwi Crater, Ghana
When one stumbles upon a natural lake that is almost perfectly round, that’s a little suspicious. Such is the case with Lake Bosumtwi, a five-mile diameter body of water that lies some twenty miles southeast of Kumasi, Ghana. This was created when a 500-foot diameter meteorite hit the region some 1.3 million years ago. Efforts to study the crater closer have been complicated by the fact that the lake is difficult to get to, because of the thick rainforest that surrounds it, and the fact that the local Ashanti people consider it to be sacred (they consider it forbidden to touch the water with iron or use metal boats, making drilling for nickel on the bottom problematic.) Still, it remains one of the best-preserved craters on the planet today, and an example of the destructive power of megarocks from the stars.

8. Mistastin Lake, Labrador, Canada
At a “mere” 38 million years old, the Mistastin crater from Labrador, Canada, is an impressive eleven-by-seven mile hole in the ground which, due to erosion from the many glaciers that has scoured that part of Canada over millions of years, was likely originally far larger than it is today. What’s unique about this crater is that, unlike most meteor impacts, this one is elliptical in nature rather than circular, suggesting that the rock hit at a shallow angle, rather than straight on like most big impacts. Even more unusual is that there is a small island in the middle of the lake which could be the central uplift of a complex crater structure, making it even cooler.

7. Gosses Bluff, Northern Territory, Australia
Equally impressive from both the ground and the air, this 142-million-year old, 15-mile diameter crater, near the center of Australia, was created when an asteroid, estimated to have been a good 15 miles in diameter, hit the surface at an impressive 40,000 MPH, gouging out a hole some 16,000 feet deep. That’s the energy equivalent to 22,000 megatons of TNT, suggesting that life on the continent likely had a difficult time in the immediate aftermath of this little incident. Now one of the most significant impact structures in the world, the highly eroded crater stands as a stark reminder of the power one big rock can have.

6. Clearwater Lakes, Quebec, Canada
It’s cool enough to find one meteor crater, but to find two of them side-by-side is twice as cool. This is exactly what happened when an asteroid split in two upon entering the Earth’s atmosphere some 290 million years ago, creating two monster impact craters on the eastern shore of Hudson Bay. Since then, erosion and glaciers have eroded much of the original craters away, but what remains is still impressive. One lake is some twenty miles in diameter and the other just under fourteen. Given the amount of erosion that has occurred over the last 290 million years, one can only speculate how much larger they must’ve been when first created.

5. The Tunguska Explosion, Siberia, Russia
This one is a little controversial, as it didn’t leave any pieces of itself, making it a source of debate as to what exactly it was that hit this little corner of Siberia a mere 105 years ago. The only thing that’s known for certain is that something pretty big, and moving very fast, exploded near Russia’s Tunguska River in June of 1908, leaving over 800 square miles of forest flatter than a squirrel on the freeway at rush hour. So large was the explosion in fact, that it was detected on instruments as far away as Great Britain! Since no bits of meteorite have ever been found, some believe the object may not have been a meteor at all, but a small chunk off a comet (which, if true, would account for the lack of meteoric material.) To further muddy the waters, there are also those who contend that what actually exploded was an alien spaceship. While completely unsubstantiated and totally speculative, we gotta admit it’s a pretty fun theory.

4. Manicouagan Crater, Canada
Manicouagan Reservoir, also known as the “eye of Quebec,” was created some 212 million years ago, when a 3-mile wide asteroid hit the Earth. The 62-mile-wide hole that it left has been worn away by the passing of glaciers and other erosive processes, but it remains impressive nonetheless. What’s especially unique about this particular crater is that, instead of just filling with water to become a near-perfect circular lake, this one is mostly dry land, ringed by a natural mote. That would make it a great place to build a castle, one might imagine.

3. Sudbury Basin, Ontario, Canada
What’s with Canada and impact craters? It appears that Alanis Morrisette’s beloved homeland has an inordinate number of meteor craters, with the one near Sudbury, Ontario being the largest of the bunch. 40 miles long, 16 miles wide, and 9 miles deep, this 1.85 billion year old crater is actually home to some 162,000 people and a number of mining companies, who discovered over a century ago that the bottom of the basin is super rich in nickel because of the asteroid. Rich enough, in fact, to provide about 10% of the world’s nickel supply!

2. Chicxulub Crater, Mexico
This is the one that may have done in the dinosaurs, and is one of the largest meteor strikes in Earth’s history. The impact happened roughly 65 million years ago, when an asteroid the size of a small city crashed onto Earth with the destructive power of 100 teratons of TNT. That’s one billion kilotons for those of you keeping score. Compare that to the Hiroshima bomb, which released the equivalent of just 20 kilotons of TNT and you get the idea. Not only did it leave a 105-mile diameter hole in the ground, but it created mega-tsunamis, earthquakes, and volcanic eruptions around the globe, that dramatically altered the environment and doomed our reptilian friends (along with a lot of other critters, it appears.) Buried beneath the Yucatan Peninsula in Mexico near the village of Chicxulub (after which it is named,) this vast crater can only be discerned from space, which is why it took so long for scientists to find it.

1. Vredefort Dome, South Africa
While the Chicxulub Crater is better known, it’s a mere pothole compared to the 186-mile-wide Vredefort Dome in South Africa, which currently holds the record for being the largest impact crater on Earth. Fortunately, in hitting over two billion years ago, the meteor/asteroid (estimated to be about six miles in diameter) didn’t do a lot of damage to life on Earth, as there were no multi-cellular organisms around at the time, or things could have gotten dicey. No doubt it adversely affected Earth’s climate at the time - not that anyone noticed, of course. Today, the original crater is mostly eroded away, but what remains is still impressive when seen from space, and serves as a graphic reminder of just how scary our little corner of the universe can be.

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