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10-03-2024, 07:04 PM
(This post was last modified: 10-03-2024, 07:05 PM by Thumpalumpacus.)
K/T extinction -- 2nd asteroid
Quote:The huge asteroid that hit Earth and wiped out the dinosaurs 66 million years ago was not alone, scientists have confirmed.
A second, smaller space rock smashed into the sea off the coast of West Africa creating a large crater during the same era.
It would have been a “catastrophic event”, the scientists say, causing a tsunami at least 800m high to tear across the Atlantic ocean.
Dr Uisdean Nicholson from Heriot-Watt University first found the Nadir crater in 2022, but a cloud of uncertainty hung over how it was really formed.
Now Dr Nicholson and his colleagues are sure that the 9km depression was caused by an asteroid hurtling into the seabed.
They cannot date the event exactly, or say whether it came before or after the asteroid which left the 180km-wide Chicxulub crater in Mexico. That one ended the reign of the dinosaurs.
But they say the smaller rock also came at the end of the Cretaceous period when they went extinct. As it crashed into Earth's atmosphere, it would have formed a fireball.
“Imagine the asteroid was hitting Glasgow and you’re in Edinburgh, around 50 km away. The fireball would be about 24 times the size of the Sun in the sky - enough to set trees and plants on fire in Edinburgh,” Dr Nicholson says.
An extremely loud air blast would have followed, before seismic shaking about the size of a magnitude 7 earthquake.
Huge amounts of water probably left the seabed, and later cascaded back down creating unique imprints on the floor.
It is unusual for such large asteroids to crash out of our solar system on course for our planet within a short time of each other.
But the researchers don’t know why two hit Earth close together.
https://www.bbc.com/news/articles/c62m04v0k0no
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10-03-2024, 08:42 PM
K/T extinction -- 2nd asteroid
(10-03-2024, 07:04 PM)Thumpalumpacus Wrote: But the researchers don’t know why two hit Earth close together.
Good grouping.
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10-03-2024, 09:08 PM
K/T extinction -- 2nd asteroid
(10-03-2024, 08:42 PM)airportkid Wrote: (10-03-2024, 07:04 PM)Thumpalumpacus Wrote: But the researchers don’t know why two hit Earth close together.
Good grouping.
I wonder if the asteroid didn't break up sometime before hitting. This could be addressed by chemical analysis, analyzing the craters for angles of impact, or some other method.
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10-03-2024, 09:50 PM
K/T extinction -- 2nd asteroid
Reminds of the cartoon, which I can't find now, where god is standing around and suddenly notices dinosaurs. "Dinosaurs! Fuck, fuck, fuck!", all the while hurling flaming rocks.
If you get to thinking you’re a person of some influence, try ordering somebody else’s dog around.
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10-03-2024, 09:59 PM
K/T extinction -- 2nd asteroid
Robert G. Ingersoll : “No man with a sense of humor ever founded a religion.”
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10-04-2024, 12:40 AM
K/T extinction -- 2nd asteroid
All I want to know is if one is coming this way before November, and if so can I vote for it.
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10-06-2024, 07:37 AM
K/T extinction -- 2nd asteroid
OK, a lot to unpack here:
TL;DR: This could be a volcanic caldera rather than an impact crater.
Here's a link to a copy of the scientific paper that has been widely reported by the media: 3D anatomy of the Cretaceous–Paleogeneage Nadir Crater
If correct, their findings are intriguing but not that surprising. Binary asteroids are common in our solar system. NASA flew the DART asteroid deflection mission into Dimorphos, the smaller of the binary Didymos-Dimorphis binary asteroid pair. So there's a fairly simple explanation for these results.
What's important to note is that this is an exclusively seismic study. The authors ran some geophones over the targets, fired off some shots, and have inferred the rest from the seismic reflections. The age of the crater comes from an earlier paper ( The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure) by many of the same authors and is also based on stratigraphy inferred from seismic data. Or, as the authors put it: " These data thus provide exceptional support for an impact origin based on geophysical data alone."
So nobody has actually looked at any rocks or produced an actual age. Which is a shame, because impact geology is incredibly distinctive. There's really no other interpretation for a sample full of suevite breccia (shattered impact glass) or shocked quartz. As is, there's at least one other good alternative explanation. Figure 1 in that second paper shows the "Upper Cretaceous-Paleogene volcanics" of the Grimaldi seamounts immediately to the south of the Nadir Crater (red blobs in the image below). In fact, the Nadir Crater is named after the Nadir Seamount (the red blob labeled "NS"), the closest of these seamounts. So we have volcanoes erupting in this neighborhood at the same time as the Nadir Crater formed.
When a mantle plume punches through the relatively thin seafloor crust it creates small seamounts, most of which never even reach the surface. By contrast, when the same plume has to push through thicker continental crust it tends to form large calderas like Ngorogoro, Toba, or Yellowstone. A caldera eruption would produce a crater that looks a lot like what the seismic results show.
I'm not saying that these guys are wrong, but that there are alternative interpretations that fit their data. I really hope that somebody goes out and drills this so that we can know for sure.
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10-06-2024, 07:47 AM
K/T extinction -- 2nd asteroid
(10-03-2024, 08:42 PM)airportkid Wrote: (10-03-2024, 07:04 PM)Thumpalumpacus Wrote: But the researchers don’t know why two hit Earth close together.
Good grouping.
For a good grouping visit Sudbury, Ontario. The mining town is located on and exists because of the 1.8 Billion year old Sudbury Basin, one of the largest impact craters preserved anywhere on our planet. Immediately to the north of Sudbury, Lake Wanapetei fills a 5 km wide crater formed a mere 37 Million years ago in an utterly unrelated event. Nice try God, but you can't kill Canadians that easily!
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