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Sioux Falls Scientists endorse Day the Dinosaurs Died for describing the
details of how an asteroid impact caused the extinction of the
Dinosaurs and made room for the evolution of mammals.

Day the Dinosaurs Died

Day the Dinosaurs Died (2018) - 60 minutes
Day the Dinosaurs Died at Amazon.com

66 million years ago, a seven-mile-wide asteroid collided with Earth, triggering a chain of events suspected of ending the dinosaurs' reign. But experts have long debated exactly what happened when the asteroid struck and how the giant beasts met their end. Now, scientists have uncovered compelling new clues about the catastrophe - from New Jersey to the wilds of Patagonia, and an international expedition of scientists has drilled into the impact crater off the coast of Mexico, recovering crucial direct evidence of the searing energy and giant tsunami unleashed by the asteroid. Join NOVA as scientists piece together a chilling precise unfolding of the Earth's biggest cataclysm, moment by moment. And discover how our early mammalian ancestors managed to survive and repopulate the Earth.

12-18-18 Erosion has erased most of Earth’s impact craters. Here are the survivors
A recent discovery in Greenland may bring the known list to 191. When it comes to impact craters, Earth is the pauper of the solar system. Even with a recent, still-to-be-confirmed crater discovery under Greenland’s ice, there are fewer than 200 known impact craters on the planet. Mars, for comparison, has hundreds of thousands. Produced by falling space rocks, most impact craters on Earth have been wiped away over time by wind, rain, shifting ice and the crawl of tectonic plates. Here are the 190 confirmed survivors, as recorded in the Earth Impact Database, maintained by the University of New Brunswick in Canada — plus the newcomer in Greenland. Identifying and studying such features could give scientists clues about the history of Earth, including the evolution of life itself. Researchers have tried to link various craters to the five known mass extinctions, for example. But only the space rock that created Chicxulub, hidden under Mexico’s Yucatán Peninsula and the Gulf of Mexico, is widely accepted as causing a major die-off. That space rock left a crater 150 kilometers wide and may have done in the dinosaurs and many other creatures about 66 million years ago (SN: 2/4/17, p. 16). Popigai, in Siberia, which measures about 90 kilometers from rim to rim, might be connected to a smaller die-off of mostly marine creatures about 34 million years ago. But that’s far from settled. Chicxulub and Popigai are the largest craters dating to the last 100 million years. But the roughly 160-kilometer-wide Vredefort crater in South Africa edges out Chicxulub as the largest known ever. Estimates put Vredefort’s origin around 2 billion years ago, making it the oldest known impact crater too.

10-25-18 Splosh! How the dinosaur-killing asteroid made Chicxulub crater
It is hard to imagine billions of tonnes of rock suddenly start to splosh about like a liquid - but that is what happened when an asteroid struck the Earth 66 million years ago. Scientists have now put together a detailed picture of the minutes following the giant impact. This, remember, is the colossal event that wiped out the dinosaurs. The analysis of rocks drilled in 2016 from the leftover crater show they underwent a process of fluidisation. The pulverised material literally began to behave as if it were a substance like water. Models had predicted what should happen when a 12km-wide stony object from space punched the ground. Initially, a near-instantaneous bowl would have been created some 30km deep and up to 100km wide. Then, instabilities would have seen the sides collapse inwards and the base of the hole rebound skyward, briefly reaching higher than the Himalayas. When everything had settled down, a crater roughly 200km wide and 1km deep would remain. This is the feature that is now buried under sediments in the Gulf of Mexico, close to the port of Chicxulub. The impact description - scientists call it the dynamic collapse model of crater formation - is only possible if the hammered rocks can, for a short period, lose their strength and flow in a frictionless way. And it is the evidence for this fluidisation process that researchers now report after studying the rocks they drilled from something called the "peak ring" - essentially, a circle of hills in the centre of the remnant Chicxulub depression. "What we found in the drill core is that the rock got fragmented. It was smashed to tiny little pieces that initially are millimetre sized; and that basically causes this fluid-like behaviour that produces in the end the flat crater floor, which characterises Chicxulub and all such large impact structures, including those we also see on the Moon," explains Prof Ulrich Riller, from the University of Hamburg, Germany.

Day the Dinosaurs Died

Sioux Falls Scientists endorse Day the Dinosaurs Died for describing the
details of how an asteroid impact caused the extinction of the
Dinosaurs and made room for the evolution of mammals.