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The huge asteroid that swept over the Earth in Chicxulub, modern Mexico, 66 million years ago, was a global catastrophe that surpassed the best of modern science. In a few seconds, hundreds of gigatonnes of sulfur and carbon dioxide were projected into the atmosphere, and the shockwave triggered tsunamis and landslides around the world. Evidence of mass extinction is found around the world.
The impact was so strong that the rock sank like a liquid in the seconds and minutes that followed, creating the "peak circle" of rocks crushed around the crater, according to a new study published in Nature.
The phenomenon is known as "acoustic fluidization", according to scientists, a team of 13 people from various international institutions.
"The observations suggest a quasi-continuous rock flow and hence an acoustic fluidization, a dominant physical process controlling initial crater formation, followed by more and more localized defects," the authors write.
Their methodology: drill a six-inch core directly into the Earth. A cubic volume of 829 meters was collected, including 112 meters of post-impact pelagic carbonate rock, 130 meters of impact fusion and suevite rock and 587 meters of highly shocked target rock.
Evaluation of the base material was made by taking 25 micron thin sections and inspecting them with a Zeiss Axio Scope.A1 polarization microscope combined with a high resolution digital camera. Drill hole images of the planar structure were also captured en route and are compatible with each other by the ALT WellCAD software system.
The computer modeling of the impact was a cross reference, taking the dominant model of the asteroid making 14 km in diameter and traveling 12 km per second (although other models have suggested he was moving faster, even at 18 km per second).
Simulations have shown that the "circle of peaks" created around the crater, itself several kilometers deep and more than 115 kilometers wide, must have been created by rocks moving smoothly and less like a solid.
According to their calculations, the entire creation of the "critical circle" took place in just five minutes.
"For a while, the broken rock behaves like a fluid," said Jay Melosh, one of Purdue University's authors. "Many theories have been proposed about the mechanism that allows this fluidization, and now we know that it is very strong vibrations that shake the rock enough to let it flow."
The lessons could potentially be useful to humans from the Holocene times, Melosh said.
"The cities were swept by huge landslides, where people thought they were safe, but then discovered that the rock would flow like a liquid when disturbances would create a large enough mass in motion," Melosh said. . "These discoveries help to understand how crater collapse and the behavior of large masses of rock are similar to those of a fluid under other circumstances, such as landslides. field and earthquakes. "
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