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Scientists 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? What might they 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 cover 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?

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.

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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.