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2019 Science Stats

Sioux Falls Scientists endorse Mass Extinction for describing how an asteroid impact caused the extinction of the Dinosaurs and a huge volcanic
eruption in Siberia caused the extinction of 95% of all life on earth.

Mass Extinction
Life at the Brink

Mass Extinction: Life at the Brink. (2014) - 60 minutes
Mass Extinction at Amazon.com

The Clues to the Future Lie in the Past

It's a mystery on a global scale: five times in Earth's past, life has been nearly extinguished, the vast majority of plants and animals annihilated in a geologic instant. What triggered these dramatic events? and What might they tell us about the fate of our world?

Mass Extinction: Life at the Brink joins scientists around the globe as they unravel the mysteries of two of the most dramatic mass extinctions - the "K/T Extinction" that wiped out the dinosaurs, and "The Great Dying," which obliterated nearly 90% of all Earth's species. At first glance, these two extinctions couldn't look more different. A six-mile-wide asteroid spelled near-instant doom for the dinosaurs. And as new research covered in the film reveals, massive volcanic eruptions altered the chemistry of the atmosphere and ocean to trigger "The Great Dying." As different as they seem, these two extinctions share uncanny similarities and a message for today. Could the impact of human beings be just as devastating to the planet as a massive asteroid strike or volcanic eruptions?

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.

2-12-18 Ancient ozone holes may have sterilized forests 252 million years ago
Barren trees could have collapsed food webs, leading to Earth’s greatest mass extinction. Volcano-fueled holes in Earth’s ozone layer 252 million years ago may have repeatedly sterilized large swaths of forest, setting the stage for the world’s largest mass extinction event. Such holes would have allowed ultraviolet-B radiation to blast the planet. Even radiation levels below those predicted for the end of the Permian period damage trees’ abilities to make seeds, researchers report February 7 in Science Advances. Jeffrey Benca, a paleobotanist at the University of California, Berkeley, and his colleagues exposed plantings of modern dwarf pine tree (Pinus mugo) to varying levels of UV-B radiation. Those levels ranged from none to up to 93 kilojoules per square meter per day. According to previous simulations, UV-B radiation at the end of the Permian may have increased from a background level of 10 kilojoules (just above current ambient levels) to as much as 100 kilojoules, due to large concentrations of ozone-damaging halogens spewed from volcanoes (SN: 1/15/11, p. 12). Exposure to higher UV-B levels led to more malformed pollen, the researchers found, with up to 13 percent of the pollen grains deformed under the highest conditions. And although the trees survived the heightened irradiation, the trees’ ovulate cones — cones that, when fertilized by pollen, become seeds — did not. But the trees weren’t permanently sterilized: Once removed from extra UV-B exposure, the trees could reproduce again.

2-7-18 The worst mass extinction may have begun with mass sterilisation
There seems to have been a surge in ultraviolet radiation during the Permian extinction 252 million years ago, and it might have left plants infertile rather than kill them. We may have misunderstood the mother of all extinctions. The gargantuan Permian extinction has been blamed on massive volcanic eruptions that killed swathes of organisms, but the eruptions may instead have had an insidious effect: sterilisation. Organisms may not have been killed outright, but if they could not reproduce their species were still doomed. Almost all complex life died 252 million years ago at the end of the Permian period. The causes have long been debated. About a decade ago geologists began noticing something odd about fossil pollen from the time. An unusually high number of the pollen grains were malformed or under-developed. That might be because the volcanic activity at the time released ozone-destroying chemicals into the atmosphere. As a result, more of the sun’s harmful ultraviolet-B (UV-B) radiation reached Earth’s surface. The UV-B would have stressed plants, particularly the abundant conifers and seed ferns, which suffered during the extinction. To mimic this environmental upheaval, Jeffrey Benca, Ivo Duijnstee and Cindy Looy at the University of California, Berkeley exposed 18 dwarf conifers to elevated UV-B levels for 56 days. The tiny trees produced elevated levels of malformed pollen, as predicted. But something unexpected happened. Although the trees survived UV-B exposure, they were all rendered infertile throughout. The pines made seed cones, but these died before they grew large enough to be fertilised. “The shrivelled-up seed cones were a big surprise,” says Looy.

Mass Extinction
Life at the Brink

Sioux Falls Scientists endorse Mass Extinction for describing how an asteroid
impact caused the extinction of the Dinosaurs and a huge volcanic
eruption in Siberia caused the extinction of 95% of all life on earth.