https://www.nationalgeographic.com/premium/article/have-scientists-found-800000-year-ol...

"'Tektites,” announced the cashier, handing over a photocopied paper that indicated they formed in a mysterious meteorite strike—Earth’s last major impact, in fact, a catastrophic collision that could have been witnessed by ancient human relatives. As Sieh read about a colossal debris field covering 20 percent of the planet’s landmass, from China to Antarctica, he realized a key detail was missing.

“'I thought, oh my gosh. How could it be that nobody's found the hole?” Now, a dozen years later, Sieh is convinced he has.

"After his jewelry store encounter, Sieh studied the scientific literature and searched satellite images across the region for geological features of interest. He began to suspect that the missing crater, formed some 800,000 years ago, could be in the Bolaven Plateau in southern Laos, buried beneath a young but extensive lava field.

***

"These geologic sequences were recorded and measured at hundreds of sites across a 310-mile-wide region on and around the plateau, revealing a radial pattern of thickening deposits that converges on the plateau center. Sieh describes his case for the Bolaven Plateau as now “all but indisputable.”

“'To have a rubbly, poorly sorted deposit made up of stuff we think is from where the crater was, [and] to have it thicken and coarsen toward the source, toward the plateau … offer me some other explanation,” he says.

"But not all scientists are yet convinced. Fred Jourdan, a geochronologist at Curtin University in Perth, Australia, who has used chemical clues from the tektites to date the impact to about 788,000 years ago, says Sieh’s proposal is “very well possible,” though he believes the new findings only offer indirect evidence. He says the study is “not a demonstration of the absolute location,” pointing out that many volcanically active places across Southeast Asia also have sandy surface geology that could have produced the tektites in an impact.

***

"In the absence of an impact crater, tektite strewn fields provide the next best record of Earth-shattering meteorite strikes.

"Jourdan’s 2019 dating of the tektites, found today across much of Australia and Southeast Asia, made it the youngest of Earth’s four major tektite strewn fields. The date fueled speculation that ancient Asian hominins such as Homo erectus could have witnessed the explosive event. While a limited fossil record makes that difficult to prove, this planetary collision was clearly best viewed from afar—Jourdan’s analysis showed the tektites formed at temperatures of up to 7,200 degrees Fahrenheit.

***

"While Carling’s paper focuses on just one site, he claims to have since mapped this “impact ejecta sequence” across Thailand, southern Laos, Vietnam, and northern Cambodia. He also says that this field work has demonstrated a thickening in these deposits toward southern Laos, supporting Sieh’s case for the Bolaven Plateau as an impact site.

"Carling hopes to publish his team’s wider field analysis next year, adding more clues to this geological puzzle. For Jourdan, though, the final proof can only be found by searching deep underground. “To rally the entire impact community behind the case, they need to drill down to where they think the crater is located,” he says.

"Carling believes an exploration down to about 600 or 700 feet might suffice to find other features like shatter cones, shocked minerals, and melt rocks—all signs of a major impact. “We might also find fragments of the meteor itself,” he says."

Comment: it took many years to have Chixculub accepted. The problem here is not surprising. Areal surveys see craters all over the Earth.

https://www.sciencealert.com/even-without-a-meteorite-the-stage-was-set-for-dinosaurs-t...

"A new analysis by an international team of researchers has added evidence to claims that the world prior to the asteroid blow was anything but paradise, with measures of sulfur in the atmosphere reaching critical levels.

"Together with other studies on levels of mercury, the research provides a signature of volcanic activity strong enough to cause significant climate disruptions.

***

"'Our data suggest that volcanic sulfur degassing from such activity could have caused repeated short-lived global drops in temperature," University of Oslo geoscientist Sara Callegaro and colleagues write in their paper.

"The team examined rocks from the Deccan Traps – one of the largest volcanic features – in what's now West India. They applied a new technique they developed for measuring sulfur concentrations.

"Models suggest sustained sulfur emissions from the Deccan Traps were enough to substantially alter the global climate. This volcanic region alone released a staggering one million cubic kilometers of molten rock.

"What's more, formation of the highly concentrated sulfur containing lava at Thakurvadi to Bushe, within the region, coincides with the cooling Cretaceous climate, the team notes.

"While much of the basalt in the area is generally low in sulfur, this could indicate the climate – cooling molecule was slowly released into the atmosphere from the hardened magma following eruptions.

"As a result global temperatures could have plummeted in bouts of up to 10°C, between rapid recovery periods, within 100,000 years before the Chicxulub meteor delivered that final blow.

"'Our research demonstrates that climatic conditions were almost certainly unstable, with repeated volcanic winters that could have lasted decades, prior to the extinction of the dinosaurs, " explains McGill University geochemist Don Baker.

"'This instability would have made life difficult for all plants and animals and set the stage for the dinosaur extinction event."

"Fossilized bone fragments and thousands of eggshell remnants have suggested a global decline in non-avian dinosaur species over such a prolonged time period.

"But these declines have been contradicted by other studies, continuing a long-standing and sometimes bitter scientific debate between the asteroid and volcano theories. Some researchers suggest the asteroid may have triggered greater activity from the Deccan Traps, others claim the volcanic activity may have even helped life recover from the asteroid strike.

"The argument for pulses of eruptions does seem to be stacking up and volcanoes are, after all, what brought three quarters of all life on Earth to an end during the previous mass extinction.

"'Deccan Traps volcanism set the stage for a global biotic crisis, repeatedly deteriorating environmental conditions by forcing recurring short volcanic winters," the team concludes."

Comment: it seems Chixculub was the final blow. Dr. Gerald Schroeder wrote God might have caused the asteroid to hit.

https://www.sciencealert.com/ancient-black-box-hints-at-what-really-killed-the-dinosaurs

"Originally proposed as a mechanism in 1980 by the geologists who uncovered the first signs of the mighty impact, the hypothesis was ruled out in the early 2000s because rock samples from this era didn't contain enough fine dust to cause a global winter.

"However, most previous studies were based on one-centimeter-thick layers of sediment from the Cretaceous-Paleogene period.

"This new study analyzed 40 samples of sediment taken from a much richer, 1.3-metre-deep deposit in Tanis, North Dakota. This site is 3,000 kilometers (about 1,900 miles) north of the Chicxulub asteroid crater, but it provides a unique snapshot of how plumes of dust, soot, and particles spread in the years post-impact.

"Larger particles scatter light at smaller angles than finer particles, so using a laser, the researchers were able to determine how much of each sample was made up of fine silicate dust in the 0.8 to 8 micrometer range.

"'[We found] a larger contribution of fine dust… than previously appreciated," wrote the researchers.

"Using computer modeling, the researchers discovered that this fine dust – created when the asteroid hit the Earth and pulverized the rock underneath – was "the most lethal" of the particles released when the 10 to 15-kilometer-wide meteorite collided with Earth.

"They found that high levels of dust in the atmosphere would have created a global darkness lasting almost two years, which would have made it impossible for plants to photosynthesize.

"Without plants, the entire food chain would have collapsed. The top predators – like Tyrannosaurus rex – hunted prey that depended on plants as part of their diet.

"This dust could have stayed suspended in the air for up to 15 years, causing a 15°C fall in global temperatures and inducing a "photosynthetic shut-down for almost two years post-impact" by blocking sunlight, the researchers wrote.

"When the Chicxulub asteroid hit Earth, it created plumes of dust, sulfur, and sparked wildfires that generated soot.

"The shock of the collision also would have vaporized rock and produced sulfur-bearing gasses that form into small particles high in the atmosphere. And the intense heat produced by the asteroid's impact would have sparked large-scale wildfires, sending large amounts of soot and ash into the sky.

"Yet according to the researcher's results, it was the fine silicates rather than material like sulfur particles that were primarily responsible for the extended planetary winter.

"The Chicxulub crater is named after the town of Chicxulub Pueblo that sits at the center of its 150-kilometer boundaries. There are around 350 sites around the world where geologists can eyeball this tumultuous period by studying layers of sediment.

"'We find that the global darkness and prolonged loss in the planet's photosynthetic activity occur only in the silicate dust scenario, up to nearly 1.7 years (620 days) after impact," the researchers wrote.

"'This constitutes a sufficiently long timescale to pose severe challenges for both terrestrial and marine habitats."

"Those animals and plants that were not adapted or could not adapt to live in the dark and cold would have met their demise. Flora and fauna with flexible diets, habitats, and lifestyles would have had a greater chance of survival. (my bold)

"The Chicxulub asteroid impact also unleashed a mega-tsunami 1.5-kilometres tall that hit every continent on Earth, and set off seismic activity 50,000 times more powerful than the 2004 Sumatra earthquake."

Comment More evidence for the asteroid impact killing off the dinosaurs. All that could eat, survived, as one might suspect.

https://aeon.co/essays/earths-story-is-not-about-dynasties-but-communities?utm_source=A...

"The worst day in the entire history of life on Earth happened in the northern springtime. On that day, the last of the Age of Dinosaurs, a roughly seven-mile-wide chunk of rock that had been hurtling towards our orbit for millions of years slammed into Earth’s midsection and immediately brought the Cretaceous to a close. The consequences were so dire that survival in the hours immediately following impact was merely a matter of luck.

***

"The entire reason we so often fixate on the supposed dominance of the dinosaurs is because we now see ourselves in that position. For more than a century, the decimation of the ‘ruling reptiles’ has been taken as a cautionary tale of what could happen to us –

***

"T rex existed as part of an ecosystem, both shaped by and shaping the world around it. The dinosaur could even be said to have been an ecosystem unto itself, a living animal that harboured parasites and bacteria in and outside its body (just like us). The dinosaur was large, impressive and no doubt ferocious, but it was also a living thing at the intersection of various ecological connections. To say the dinosaur ‘ruled’ anything is ridiculous, a form of fossiliferous individuality that ignores broader communities.

***

"Prior to the impact, the average dinosaur weighed about three and a half tons and was roughly the size of a small African bush elephant. Such immense animals browsed and grazed bushels of vegetation at a time, trampled pathways through the forests, pushed over trees, and left plenty of chlorophyll-packed dinosaur pats to keep prehistoric dung beetles busy. Every choice a dinosaur like the three-horned Triceratops or shovel-beaked Edmontosaurus made altered the landscape in some fashion, from busting up rotting logs inhabited by invertebrates to creating shallow ponds in areas where they frequently churned the soil. Big dinosaurs kept the forests open and clustered together, their appetites and footfalls altering the shape of the forest itself. But now they are all gone, leaving forests to grow thick and tall.

***

"We are living through an ecological crisis of our own making. The loss of every species, whether documented by science or not, is not just another tally of biodiversity’s losses. When a species vanishes, it leaves a void in its ecosystem. The way those living things uniquely interacted with the world vanishes, nudging adjustments in the ecosystem that once hosted the species. The extinction of a plant might alter nutrient cycling in a patch of forest of what plants a herbivore eats. The disappearance of a carnivore might make prey populations more vulnerable to disease if another predator doesn’t take up its role. A large herbivore’s population crashes and forests grow differently, some plants losing a means to disperse their seeds and others growing thicker in the absence of large feet trampling down trails through the woodland.

"Evolution and extinction are bound together in these small, often-invisible interactions between species, the connections that continually shape the unique nature of life on our planet. In our present moment, we are not only playing a role in which lineages will survive and which will disappear. Our actions are also cutting through life’s web, affecting entire communities and ecosystems that will test the resilience of more species than we’ll ever count. (my bold)

"The history of life on Earth cannot be encapsulated as a balance sheet of losses and gains through time. Nor can our present moment be understood as different groups of creatures ceding the way for each other as life climbs the rungs of progress. The reality, like life itself, is messy. Comprehending what transpired 66 million years ago – or even in this moment – requires that we look beyond the details of what we can discern from a given species in isolation. Every fossil bone we uncover and carefully cradle in a museum grew from nutrition derived from other forms of prehistoric life; and those food sources, in turn, built their tissues from plants that took up essential components from the soils, enriched by the decay of yet other creatures that came before. Wherever we find life, one existence touches another, enmeshed and setting the conditions for what might appear tomorrow." (my bolds)

Comment: when God created evolution, He knew that His creation of the vast bush of life would be an enormous totally interlocking system of related ecosystems. The part of this essay I had to skip, describes the interplay of animal effects on how their activities effect every ecologic environment they live in. The bush is required as a positive modeling of the Earth and as a food supply for all living things, including humans. Everybody is everybody's food.

https://www.sciencealert.com/risk-of-giant-asteroids-hitting-earth-could-be-worse-than-...

"NASA's Goddard Space Flight Center chief scientist, James Garvin, thinks we might have been misreading traces of some of the more serious asteroid strikes that have occurred within the past million years.

"If he's right, the odds of being hit by something nasty could be higher than current estimates predict.

***

"While we can scan the skies for evidence of rocks large enough to potentially put us in a world of pain, the geological record is like a ticker-tape of actual meteorite strikes stretching back through time.

"Unfortunately this record gets harder to read the further back we look, all thanks to Earth's dynamic winds, water, and tectonics constantly wearing at its surface. Even more recent events can be difficult to interpret through an accumulation of dust and biology.

"Garvin and his team used a new catalog of high-resolution satellite images to take a closer look at the weathered remains of some of the largest impact craters formed within the last million years, in an effort to better gauge their true size.

"Based on their analysis, a number of these craters feature faint rings beyond what have typically been considered their outer rims, effectively making them larger than previously presumed.

***

"It's a hypothesis worthy of debate. While we're busy getting systems in place to try to avoid the sting of a serious asteroid collision, odds are good that Earth's path will be clear for some time to come.

"One thing our planet doesn't need is any more scars to hide."

Comment: at least we now know we can change their course. DART impact proved it.

https://www.sciencenews.org/article/dinosaurs-last-days-extinction-book-destruction-rec...

"Black begins her tale by exploring what happened in the Hell Creek area of today’s Montana, whose rocks offer what is perhaps the best record of a dinosaur habitat. This ancient ecosystem and others worldwide included far more than apex predators, such as Tyrannosaurus rex, and their prey, of course; they also hosted a wealth of creatures, including lice and other parasites.

"These ecosystems drastically changed once the space rock hit. Larger dinosaurs, as well as any smaller creatures unable to shelter in burrows, for example, couldn’t escape the destruction.

"Despite the title, the largest part of Black’s book recounts how life rebounded in the 1 million years after the impact. Forest floors served as natural seed banks to feed surviving insects, birds and small mammals. These seeds, some of which had previously evolved to withstand wildfires, were also the sources of forests that grew back. Those initial forests were stubby and dominated by ferns for years. Some ecosystems — especially freshwater lakes and rivers whose waters were chemically buffered from acid rain by dissolved carbonates derived from limestones — emerged relatively unscathed and so species persisted there.

"...the dinosaur-killing impact was so abrupt and caused such extreme environmental changes that most species couldn’t adapt. In fact, she notes, animals and plants that weren’t already preadapted to the new state of affairs rapidly succumbed and thus left no descendants.

"Yet in devastation lay opportunities: Ecological roles that had been occupied by dinosaurs for at least 100 million years were suddenly available, setting the stage for the slow but steady rise of mammals and the world we inhabit today

"While engaging and approachable, The Last Days of the Dinosaurs is scrupulously rooted in information gathered by paleontologists, geologists, astronomers, physicists and ecologists. In vignettes at the end of each chapter, Black explores what was unfolding at locales far from Hell Creek. In an extensive appendix, she painstakingly helps readers sort through what’s fact and what’s speculation in those scenes. For example, the behaviors of burrowing mammals during the impact and its aftermath are presumed to be similar to those inferred from the fossils of similarly sized mammals that lived a few million years earlier."

Comment: An amazing sudden environmental change that forced evolution into totally new directions. Gerald Schroeder, the orthodox Jewish particle physicist, wondered if God thru the rock. Note the author's emphasis on ecosystems. dhw is not just food but part and parcel of the evolutionary process.

https://www.sciencemag.org/news/2021/07/giant-tsunami-dino-killing-asteroid-impact-reve...

"When a giant space rock struck the waters near Mexico’s Yucatán Peninsula 66 million years ago, it sent up a blanket of dust that blotted out the Sun for years, sending temperatures plummeting and killing off the dinosaurs. The impact also generated a tsunami in the Gulf of Mexico that some modelers believe sent an initial tidal wave up to 1500 meters (or nearly 1 mile) high crashing into North America, one that was followed by smaller pulses. Now, for the first time, scientists have discovered fossilized megaripples from this tsunami buried in sediments in what is now central Louisiana.

***

"To look for ancient buried structures, researchers rely on seismic imaging techniques to “see” underground. They set off explosives or use industrial hammers to send seismic waves into the earth, and listen for reflections from the layers of sediment and rock below. Companies use the technique to search for oil and gas, and they have mountains of data—especially in areas such as the Gulf of Mexico.

***

"When Kinsland and his colleagues analyzed a layer about 1500 meters underground—one associated with the time of the impact—they saw fossilized ripples. These “megaripples” were spaced up to 1 kilometer apart and were an average of 16 meters tall, they reported in an Earth & Planetary Science Letters study posted online on 2 July.

"Kinsland believes the ripples are the imprint of the tsunami waves as they approached the shore in waters about 60 meters deep, disturbing the seafloor sediments. (Tidal waves gain their massive height only when they reach the ramp of the coastline.)

***

"The discovery is the latest in a flurry of research about the Chicxulub impact, which was first hypothesized in the 1980s. Cores from the 2016 drilling expedition helped explain how the impact crater was formed and charted the disappearance and recovery of Earth’s life. In 2019, researchers reported the discovery of a fossil site in North Dakota, 3000 kilometers north of Chicxulub, that they say records the hours after the impact and includes debris swept inland from the tsunami."

Comment: Not surprising. Be sure to look at the seismic 'picture' of the giant ripples.

https://www.sciencenews.org/article/dinosaur-killing-asteroid-tropical-forest-fossil

"The day before a giant asteroid hit Earth 66 million years ago, a very different kind of rainforest thrived in what is now Colombia. Ferns unfurled and flowering shrubs bathed in the sunlight that streamed down through large gaps in the canopy between towering conifers.

"Then the bolide hit and everything changed. That impact not only set off a massive extinction event that wiped out more than 75 percent of life on Earth, but it also redefined Earth’s tropical rainforests, transforming them from sun-dappled, open-canopied forests into the dark, dense, lush, dripping forests of today’s Amazon, researchers report April 2 in Science.

"'A single historical accident changed the ecological and evolutionary trajectory of tropical rainforests,” says Carlos Jaramillo, a paleopalynologist — someone who studies ancient pollen — at the Smithsonian Tropical Research Institute in Panama City. “The forests that we have today are really the by-product of what happened 66 million years ago.”

***

"The reasons why aren’t wholly clear. The region’s climate at the end of the Cretaceous Period 66 million years ago was similar to how it is today: hot and humid. But other factors were likely at work. Huge plant-eating sauropods, the long-necked dinosaurs, would have helped maintain the open gaps, letting light in, Jaramillo says (SN: 11/17/20). Once the asteroid hit, those dinosaurs were out of the picture. Extinction of certain plant families due to the impact also may have played a role, he says.

"A third likely factor was a shift in the chemical composition of the forest soil. Frequent rainfall during the warm, wet Cretaceous leached the soils of many nutrients, which would have favored gymnosperms like conifers, says Jaramillo. “The gymnosperms had this amazing ability to grow with very little food, and could outcompete the angiosperms.”

***
"This is the first comprehensive picture of what happened in tropical ecosystems right after the extinction event, says paleoecologist Elena Stiles of the University of Washington in Seattle, who was not connected with the study. Most previous work on the chunks of time immediately before and after the extinction event — the very end of the Cretaceous and the start of the Paleogene Period — comes from North America, or from much farther south, such as in Patagonia, Stiles says (SN: 4/2/19). “In the tropics, there is no place where we have the boundary [between periods] preserved, [and] we have the limitation of a very fragmentary fossil record.'”

comment: Gerald Schroeder in his books about science and God wondered if God sent Chixculub. So do I.

https://phys.org/news/2021-02-asteroid-crater-case-dinosaur-extinction.html

"Researchers believe they have closed the case of what killed the dinosaurs, definitively linking their extinction with an asteroid that slammed into Earth 66 million years ago by finding a key piece of evidence: asteroid dust inside the impact crater.

"Death by asteroid rather than by a series of volcanic eruptions or some other global calamity has been the leading hypothesis since the 1980s, when scientists found asteroid dust in the geologic layer that marks the extinction of the dinosaurs. This discovery painted an apocalyptic picture of dust from the vaporized asteroid and rocks from impact circling the planet, blocking out the sun and bringing about mass death through a dark, sustained global winter—all before drifting back to Earth to form the layer enriched in asteroid material that's visible today.

"In the 1990s, the connection was strengthened with the discovery of a 125-mile-wide Chicxulub impact crater beneath the Gulf of Mexico that is the same age as the rock layer. The new study seals the deal, researchers said, by finding asteroid dust with a matching chemical fingerprint within that crater at the precise geological location that marks the time of the extinction.

***

"The telltale sign of asteroid dust is the element iridium—which is rare in the Earth's crust, but present at elevated levels in certain types of asteroids. An iridium spike in the geologic layer found all over the world is how the asteroid hypothesis was born. In the new study, researchers found a similar spike in a section of rock pulled from the crater. In the crater, the sediment layer deposited in the days to years after the strike is so thick that scientists were able to precisely date the dust to a mere two decades after impact.

***

"Researchers estimate that the dust kicked up by the impact circulated in the atmosphere for no more than a couple of decades—which, Gulick points out, helps time how long extinction took.

"'If you're actually going to put a clock on extinction 66 million years ago, you could easily make an argument that it all happened within a couple of decades, which is basically how long it takes for everything to starve to death," he said.

"The highest concentrations of iridium were found within a 5-centimeter section of the rock core retrieved from the top of the crater's peak ring—a high-elevation point in the crater that formed when rocks rebounded then collapsed from the force of impact.

***

"In addition to iridium, the crater section showed elevated levels of other elements associated with asteroid material. The concentration and composition of these "asteroid elements" resembled measurements taken from the geologic layer at 52 sites around the world.

"The core section and geologic layer also have earthbound elements in common, including sulfurous compounds. A 2019 study found that sulfur-bearing rocks are missing from much of the rest of the core despite being present in large volumes in the surrounding limestone. This indicates that the impact blew the original sulfur into the atmosphere, where it may have made a bad situation worse by exacerbating global cooling and seeding acid rain.

Comment: this is now real science works. Keep searching until the key proving evidence appears. In theoretical science, the theory must be based on existing known facts, not a network of guesswork.

https://phys.org/news/2021-01-crocodiles-age-dinosaurs.html

"New research by scientists at the University of Bristol explains how a 'stop-start' pattern of evolution, governed by environmental change, could explain why crocodiles have changed so little since the age of the dinosaurs.

"Crocodiles today look very similar to ones from the Jurassic period some 200 million years ago. There are also very few species alive today—just 25. Other animals such as lizards and birds have achieved a diversity of many thousands of species in the same amount of time or less.

"Prehistory also saw types of crocodile we don't see today, including giants as big as dinosaurs, plant-eaters, fast runners and serpentine forms that lived in the sea.

***

"The rate of their evolution is generally slow, but occasionally they evolve more quickly because the environment has changed. In particular, this new research suggests that their evolution speeds up when the climate is warmer, and that their body size increases.

***

"'For our study we measured body size, which is important because it interacts with how fast animals grow, how much food they need, how big their populations are and how likely they are to become extinct."

"The findings show that the limited diversity of crocodiles and their apparent lack of evolution is a result of a slow evolutionary rate. It seems the crocodiles arrived at a body plan that was very efficient and versatile enough that they didn't need to change it in order to survive.

"This versatility could be one explanation why crocodiles survived the meteor impact at the end of the Cretaceous period, in which the dinosaurs perished. Crocodiles generally thrive better in warm conditions because they cannot control their body temperature and require warmth from the environment.

"The climate during the age of dinosaurs was warmer than it is today, and that may explain why there were many more varieties of crocodile than we see now. Being able to draw energy from the sun means they do not need to eat as much as a warm-blooded animal like a bird or a mammal.

"Dr. Stockdale added: "It is fascinating to see how intricate a relationship exists between the earth and the living things we share it with. The crocodiles landed upon a lifestyle that was versatile enough to adapt to the enormous environmental changes that have taken place since the dinosaurs were around.'"

Comment: Fascinating animals with little diversification. Note the bold about the higher temperatures in the past, a logical answer to todays climate frenzy

https://www.scientificamerican.com/podcast/episode/dinosaur-asteroid-hit-worst-case-pla...

"We all know the story: 66 million years ago, a giant asteroid crashed into Earth, killing off three-quarters of all species, including most of the dinosaurs. Researchers suspect that the impact caused the extinction by kicking up a cloud of dust and tiny droplets called aerosols that plunged the planet into something like a nuclear winter.

“'These components in the atmosphere drove global cooling and darkness that would have stopped photosynthesis from occurring, ultimately shutting down the food chain.”

***

"...scientists hypothesize that soot may also have come from the very rocks that the asteroid pulverized when it struck. If those rocks contained significant amounts of organic matter—such as the remains of marine organisms—it would have burned up on impact, sending soot shooting up into the stratosphere. In that case, soot would have spread around the globe in a matter of hours and stayed there for years. And it would have radically altered Earth’s climate.

***

"...the researchers looked at the structure and chemistry of the PAHs buried along with it. Specifically, the researchers looked for groups of atoms that stick off the rings like spikes. PAHs generated from burning wood don’t have many spikes, but PAHs from burning fossil carbon—like what would have been in the target rocks—have more.

"Lyons and her team found that most of the PAHs deposited after the impact were spiky, which suggests that soot from the rocks hit by the asteroid played a major role in the mass extinction.

“'There was more dust and more sulfate aerosols than soot, but soot is a stronger blocker of sunlight than either of those two. So a small amount of soot can drive large reductions in sunlight.”

***

"The results suggest that the devastation of this very sooty asteroid impact may be due in part to a fluke of geography: the space rock smashed into the Gulf of Mexico, where the sediments were rich in organic matter. They still are—the region produces large amounts of oil today.

“'Where it had occurred was likely one of the reasons that it led to a major mass extinction. It was kind of the perfect storm, or the perfect asteroid impact, I guess you could call it.'”

Comment: If God caused it, His aim was perfect. Seems like too much of a chance event.

https://www.sciencemag.org/news/2020/09/after-asteroid-wiped-out-dinosaurs-ocean-microb...

"The asteroid impact that killed most of the dinosaurs 66 million years ago also created conditions for ocean microbes to flourish, according to a new study. In microscopic rock crystals, researchers have found evidence that massive blooms of algae and photosynthetic bacteria covered the world’s oceans, providing food for larger marine creatures soon after the cataclysm.

"In 2016, researchers working in the Gulf of Mexico drilled into the Chicxulub crater, the scar left behind by the asteroid impact, buried under the sea floor. They found that sediments deposited immediately after the impact were rich in micrite, a calcium carbonate mineral. Calcium carbonate, common in limestone, precipitates in the world’s oceans: Corals and plankton build skeletons of it, microbes such as bacteria produce it, and it can even form directly from seawater.

***

"In addition to wiping out so much life on land, the impact decimated ocean ecosystems as well. Vaporized rock led to a buildup of sulfuric acid that rained down on oceans along with toxic metals like lead and mercury. More than 90% of marine phytoplankton went extinct, researchers have shown.

"Yet that destruction also paved the way for newcomers, says Julio Sepúlveda, a biogeochemist at the University of Colorado, Boulder, who was not involved in the research. “If you wipe out an important group from an ecosystem, you have an empty ecological niche.”

Comment: Note the last quote. Wipe out an ecosystem and another replaces it. A balanced system continues.

https://phys.org/news/2020-07-evolution-chicxulub-asteroid-impact-rapid.html

"New evidence from International Ocean Discovery Program (IODP) Expedition 364 of trace fossils of burrowing organisms that lived in the seafloor of the Chicxulub Crater beginning a few years after the impact shows just how quick the recovery of the seafloor ecosystem was, with the establishment of a well-developed tiered community within ?700,000 years after the event.

***

"The investigators concluded that the diversity and abundance of trace fossils responded primarily to variations in the flux of organic matter (i.e., food) sinking to the seafloor during the early Paleocene. Local and regional-scale effects of the K-Pg impact included earthquakes of magnitude 10-11, causing continental and marine landslides, tsunamis hundreds of meters in height that swept more than 300 km onshore, shock waves and air blasts, and the ignition of wildfires. Global phenomena included acid rain, injection of aerosols, dust, and soot into the atmosphere, brief intense cooling followed by slight warming, and destruction of the stratospheric ozone layer, followed by a longer-term greenhouse effect.

"Mass extinction events have punctuated the past 500 million years of Earth's history, and studying them helps geoscientists understand how organisms respond to stress in their environment and how ecosystems recover from the loss of biodiversity. Although the K-Pg mass extinction was caused by an asteroid impact, previous ones were caused by slower processes, like massive volcanism, which caused ocean acidification and deoxygenation and had environmental effects that lasted millions of years.

"By comparing the K-Pg record to earlier events like the end Permian mass extinction (the so-called 'Great Dying' when 90% of life on Earth went extinct), geoscientists can determine how different environmental changes affect life. There are similar overall patterns of recovery after both events with distinct phases of stabilization and diversification, but with very different time frames. The initial recovery after the K-Pg, even at ground zero of the impact, lasted just a few years; this same phase lasted tens of thousands of years after the end Permian mass extinction. The overall recovery of seafloor burrowing organisms after the K-Pg took ~700,000 years, but it took several million years after the end Permian."

Comment: What this shows is how resilient life is, as it always has recovered from extinction events, even the most severe ones.

https://www.sciencedaily.com/releases/2020/05/200526111320.htm

"New simulations from Imperial College London have revealed the asteroid that doomed the dinosaurs struck Earth at the 'deadliest possible' angle.

"The simulations show that the asteroid hit Earth at an angle of about 60 degrees, which maximised the amount of climate-changing gases thrust into the upper atmosphere.

"Such a strike likely unleashed billions of tonnes of sulphur, blocking the sun and triggering the nuclear winter that killed the dinosaurs and 75 per cent of life on Earth 66 million years ago.

***

"Pivotal to diagnosing the angle and direction of impact was the relationship between the centre of the crater, the centre of the peak ring -- a ring of mountains made of heavily fractured rock inside the crater rim -- and the centre of dense uplifted mantle rocks, some 30 km beneath the crater.

"At Chicxulub, these centres are aligned in a southwest-northeast direction, with the crater centre in between the peak-ring and mantle-uplift centres. The team's 3D Chicxulub crater simulations at an angle of 60 degrees reproduced these observations almost exactly.

"The simulations reconstructed the crater formation in unprecedented detail and give us more clues as to how the largest craters on Earth are formed. Previous fully 3D simulations of the Chicxulub impact have covered only the early stages of impact, which include the production of a deep bowl-shaped hole in the crust known as the transient crater and the expulsion of rocks, water and sediment into the atmosphere.

"These simulations are the first to continue beyond this intermediate point in the formation of the crater and reproduce the final stage of the crater's formation, in which the transient crater collapses to form the final structure. This allowed the researchers to make the first comparison between 3D Chicxulub crater simulations and the present-day structure of the crater revealed by geophysical data."

Comment: Certainly suggestive that it might have been planned. It certainy appears fine-tuning may have played a role.

https://phys.org/news/2020-06-asteroid-impact-volcanoes-earth-uninhabitable.html

"Modelling of the Chicxulub asteroid impact 66 million years ago shows it created a world largely unsuitable for dinosaurs to live in.

"The asteroid, which struck the Earth off the coast of Mexico at the end of the Cretaceous era 66 million years ago, has long been believed to be the cause of the demise of all dinosaur species except those that became birds.

"However, some researchers have suggested that tens of thousands of years of large volcanic eruptions may have been the actual cause of the extinction event, which also killed off almost 75% of life on Earth.

"Now, a research team from Imperial College London, the University of Bristol and University College London has shown that only the asteroid impact could have created conditions that were unfavourable for dinosaurs across the globe.

"They also show that the massive volcanism could also have helped life recover from the asteroid strike in the long term.

"'We show that the asteroid caused an impact winter for decades, and that these environmental effects decimated suitable environments for dinosaurs. In contrast, the effects of the intense volcanic eruptions were not strong enough to substantially disrupt global ecosystems.

"'Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide."

***

"'In this study we add a modelling approach to key geological and climate data that shows the devastating effect of the asteroid impact on global habitats. Essentially, it produces a blue screen of death for dinosaurs."

"Although volcanoes release Sun-blocking gases and particles, they also release carbon dioxide, a greenhouse gas. In the short term after an eruption, the Sun-blockers have a larger effect, causing a 'volcanic winter'. However, in the longer term these particles and gases drop out of the atmosphere, while carbon dioxide stays around and builds up, warming the planet.

"After the initial drastic global winter caused by the asteroid, the team's model suggests that in the longer term, volcanic warming could have helped restore many habitats, helping new life that evolved after the disaster to thrive."

Comment: From either cause they are gone, but this study adds to our knowledge, and we've still ended up with beautiful birds.

https://www.sciencenews.org/article/chicxulub-collision-earth-crust-hot-water-microbes-...

"The asteroid that slammed into Earth 66 million years ago left behind more than a legacy of mass destruction. That impact also sent superheated seawater swirling through the crust below for more than a million years, chemically overhauling the rocks. Similar transformative hydrothermal systems, left in the wake of powerful impacts much earlier in Earth’s history, may have been a crucible for early microbial life on Earth, researchers report May 29 in Science Advances.

***

"One of those researchers was planetary scientist David Kring of the Lunar and Planetary Institute in Houston. A dozen years earlier, Kring had found evidence at Chicxulub that the layers of rock bearing the signs of impact — telltale features such as shocked quartz and melted spherules — were subsequently cut through by veins of newer minerals such as quartz and anhydrite. Such veins, Kring thought, suggest that hot hydrothermal fluids had been circulating beneath Chicxulub some time after the impact.

"Hydrothermal systems can occur where Earth is tectonically active, such as where tectonic plates pull the seafloor apart, or where mantle plumes like the one beneath Yellowstone rise up into the crust. The molten rock rising through the crust in these regions superheats water already circulating within the crust.

***

"Evidence from lunar craters suggests that Earth was heavily bombarded by asteroids about 3.9 billion years ago (SN: 10/18/04). Most of those more ancient craters on Earth have long since vanished or been altered by the constant tectonic recycling of Earth’s surface (SN: 12/18/18). So the hydrothermal system beneath Chicxulub offers a window into what such systems might have actually looked like much deeper in the past, says geophysicist Norman Sleep of Stanford University, who was not involved in the study. “It shows the reality of the process,” Sleep says.

"The new study may set the stage for the possibility of life thriving beneath an impact. But whether a microbial cast of characters was actually present beneath Chicxulub is a question for future studies, Kring says."

Comment: No wonder the dinos were killed. This also adds to the theories of the origin of life.

https://phys.org/news/2020-05-steaming-cauldron-dinosaurs-demise.html

"A new study reveals the Chicxulub impact crater may have harbored a vast and long-lived hydrothermal system after the catastrophic impact event linked to the extinction of dinosaurs 66 million years ago.

"The Chicxulub impact crater, roughly 180 kilometers in diameter, is the best preserved large impact structure on Earth and a target for exploration of several impact-related phenomena. In 2016, a research team supported by the International Ocean Discovery Program and International Continental Scientific Drilling Program drilled into the crater, reaching a depth of 1,335 meters (> 1 kilometer) below the modern-day sea floor. The team recovered rock core samples which can be used to study the thermal and chemical modification of Earth's crust caused by the impact. The core samples show the crater hosted an extensive hydrothermal system that chemically and mineralogically modified more than 100,000 cubic kilometers of Earth's crust.

***

"The team found evidence that subsurface rivers of water were heated and driven upwards towards the boundary between the floor of the impact crater and the bottom of the Yucatán sea. The hot water streamed around the edges of an approximate 3-kilometer thick pool of impact-generated magma, percolated through fractured rock, and rose to the seafloor where it vented into the sea. The hot water system was particularly intense in an uplifted range of mountains on the seafloor that form a 90 kilometer-diameter ring around the center of the crater. The rock core recovered from that peak ring is cross-cut by fossil hydrothermal conduits that are lined with multi-colored minerals, some, appropriately enough, a fiery red-orange color. Nearly two dozen minerals precipitated from the fluids as they coursed through the rock, replacing the rock's original minerals.

***

"Minerals identified in the new rock core indicate the hydrothermal system was initially very hot with temperatures of 300 to 400 °C. Such high temperatures indicate the system would have taken a long time to cool. The team determined the cooling time using a geomagnetic polarity clock. "Our results indicate that tiny magnetic minerals were created in the Chicxulub crater due to chemical reactions produced by a long-lived hydrothermal system. These minerals appear to have recorded changes in the Earth's magnetic field as they formed. Their magnetic memories suggest that hydrothermal activity within the crater persisted for at least 150,000 years," says co-author Sonia Tikoo from Stanford University.

"Further evidence for the hydrothermal system's longevity comes from an anomalously high concentration of manganese in seafloor sediments, the result of seafloor venting. Co-author Axel Wittmann from Arizona State University explains, "Similar to mid-ocean ridges, venting from marine impact craters generates hydrothermal plumes that contain dissolved and slowly oxidizing manganese, which compared to background concentrations produced enrichments up to ten-fold in post-impact sediments over 2.1 million years at Chicxulub.'"

Comment: Poor dinos! I'd love to have seen it hit, but glad I didn't.

https://www.quantamagazine.org/pincelli-hull-explains-how-an-asteroid-killed-the-dinosa...

"Researchers had long known that the Deccan Traps erupted within a few million years of the asteroid strike. But in 2015, a group based at Princeton University significantly narrowed the timing. They found that the lava began squishing out of the earth only 250,000 years before the impact and continued for 500,000 years afterward. Then last year, they estimated that a major pulse of lava erupted just tens of thousands of years before the strike. (At the same time, a Berkeley group argued instead that a big pulse began right after.)

"It may seem like an obscure chronological feud, but this one matters: If the Deccan Traps released lava and gas just before the asteroid fell, at least some of the subsequent carnage could be attributed to climate change from the volcanoes. “It made me start to think, ‘OK, this is an open question,’” Hull said.

"She didn’t think that for long. Hull went on to lead a global collaboration that, early this year, published a definitive timeline of how the mayhem played out in small ocean fossils. The team tracked changes in global temperature over time. The planet did warm up before the impact, Hull found, but then cooled back down before the asteroid arrived. And while that warming event didn’t seem to correlate to marine extinctions, over 90% of plankton species abruptly vanished after the impact. The study suggests that the major influence of the Deccan Traps was to guide the post-apocalyptic evolution of surviving species — not to drive the extinction itself.

***

"The data we were looking at in this study was actually temperature data. Then we ran a bunch of carbon-cycle models to try and see how can we simulate these temperature records. If you have that volcanism going on before the impact, it has to stop about 200,000 years before [to reproduce the temperatures we see]. And if you look at species, nothing really goes extinct at that time. All the species that have moved to higher latitudes because of the warmth, they’ve moved back down. The ecosystems did respond to this warming that’s probably due to volcanism, but they’ve also come back to their normal baseline before the impact.

"Some mass extinctions that we see in the fossil record potentially played out over hundreds of thousands of years. That’s a different set of mechanisms than in an extinction like the K-T boundary, where we’re arguing it played out over the course of hundreds of years. Hundreds of years is a human timescale. That’s what we’re doing now.

"What the study says is that the K-T extinction is perhaps a really good analogue for today because it’s so, so rapid. We’re not talking about volcanism priming the pump for extinction. Really nasty conditions for a few decades, or a few hundred years, is all it takes.

***

"And on long timescales, the cheerful note is that, as Stephen Jay Gould said, not once since life evolved has it ever gone completely extinct. Life as a whole is pretty tough. But the species that are dominant before a mass extinction, effectively, are almost never the dominant ones afterward. And so that’s extremely sobering. If you’re grumpy at humanity, then you can think, well, somebody else is going to get a chance. I’m fairly hopeful that life goes on, and when life goes on, it does really interesting and creative stuff. So that’s good. But as a human, I care about us, so that’s depressing."

Comment: This study suggests the Chixculub extinction was quick because of the volcanoes adding their contributions.

https://phys.org/news/2020-03-darkness-cold-responsible-dinosaur-killing-extinction.html

"A new study in AGU's journal Geophysical Research Letters simulates the contributions of the impact's sulfur, dust, and soot emissions to the extreme darkness and cold of the impact winter. The results show the cold would have been severe but likely not devastating enough to drive a mass extinction. However, soot emissions from global forest fires darkened the sky enough to kill off photosynthesizers at the base of the food web for well over a year, according to the study.

"'This low light seems to be a really big signal that would potentially be devastating to life," said Clay Tabor, a geoscientist at the University of Connecticut and lead author of the new study. "It seems like these low light conditions are a probable explanation for a large part of the extinction."

***

"The Chicxulub asteroid impact spewed clouds of ejecta into the upper atmosphere that then rained back down to Earth. The returning particles would have had enough energy to broil Earth's surface and ignite global forest fires. Soot from the fires, along with sulfur compounds and dust, blocked out sunlight, causing an impact winter lasting several years. Previous research estimates average global temperatures plummeted by at least 26 degrees Celsius (47 degrees Fahrenheit).

***

"Their results suggest soot emissions from global fires absorbed the most sunlight for the longest amount of time. The model showed soot particles were so good at absorbing sunlight that photosynthesis levels dropped to below one percent of normal for well over a year.
"Based on the properties of soot and its ability to effectively absorb incoming sunlight, it did a very good job at blocking sunlight from reaching the surface," Tabor said. "In comparison to the dust, which didn't stay in the atmosphere for nearly as long, and the sulfur, which didn't block as much light, the soot could actually block almost all light from reaching the surface for at least a year."

"The darkness would have been devastating to photosynthesizers and could explain the mass extinction through a collapse of the food web, according to the researchers. All life on Earth depends on photosynthesizers like plants and algae that harvest energy from sunlight.
Interestingly, the temperature drop likely wasn't as disturbing to life as the darkness, according to the study.

"'It's interesting that in their model, soot doesn't necessarily cause a much larger cooling when compared other types of aerosol particles produced by the impact-but soot does cause surface sunlight to decline a lot more," said Manoj Joshi, a climate dynamics professor at the University of East Anglia in the United Kingdom who was not connected to the new study."

Comment: However it happened, the dinos are gone

https://www.sciencedaily.com/releases/2020/02/200210144852.htm

"An emerging scientific consensus is that gases -- in particular carbon gases -- released by volcanic eruptions millions of years ago contributed to some of Earth's greatest mass extinctions. But new research at The City College of New York suggests that that's not the entire story.

"'The key finding of our research is that carbon from massive, ancient volcanic eruptions does not line up well with the geochemical clues that tell us about how some of Earth's most profound mass extinctions occurred," said Benjamin Black, assistant professor in CCNY's Division of Science, whose expertise includes effects of volcanism on climate and mass extinctions.

***

"The new data does not rule out volcanism as the culprit in driving past mass extinctions, the article points out. But it does conclude that there must have been something extra at work."

Comment: Again shown that volcanoes did n ot play a major role.