January 31, at am. Scientists are assembling the most detailed timeline yet of the dino apocalypse. They are giving fresh scrutiny to telltale fingerprints left by the fateful event so long ago. Mountains formed in mere minutes.
In North America, a towering tsunami buried plants and animals alike under thick piles of rubble. Lofted debris darkened skies around the world. The planet chilled — and stayed that way for years. Life may already have been in trouble. Growing evidence points to a supervolcanic accomplice. Eruptions in what is now India spewed out molten rock and caustic gases.
These may have acidified the oceans. All of this could have destabilized ecosystems long before and after the asteroid hit. The jolt of that impact may even have boosted the eruptions, some researchers now argue.
As more clues have emerged, some seem to conflict. He is a geoscientist at the Berkeley Geochronology Center in California. What is clear is that a massive die-off took place around 66 million years ago.
It is visible in the layers of rock that mark the boundary between the Cretaceous and Paleogene periods. Fossils that were once abundant no longer appear in rocks after that time. Studies of fossils found or not found across the boundary between these two periods — abbreviated the K-Pg boundary — show that some three out of every four plant and animal species went extinct at about the same time. This included everything from the ferocious Tyrannosaurus rex to microscopic plankton.
Over the years, scientists have blamed many suspects for this catastrophic die-out. Some have suggested global plagues struck. Or maybe a supernova fried the planet. In , a team of researchers including father-son duo Luis and Walter Alvarez reported discovering lots of iridium in places worldwide. That element appeared along the K-Pg boundary. The finding marked the first hard evidence for a killer-asteroid impact.
Piles of impact debris led crater hunters to the Caribbean. Eleven years after the Alvarez paper, scientists at last identified the smoking gun — the hidden crater. It circled the coastal Mexican town of Chicxulub Puerto. The crater actually had been discovered in the late s by oil company scientists.
Word of that find, however, did not reach crater hunters for years. Based in part on the gaping size of the depression, scientists estimated the size of the impact.
They figured it must have released 10 billion times as much energy as the nuclear bomb dropped on Hiroshima, Japan, in Questions have remained, though, about how the impact might have caused so much death and destruction worldwide.
It was the darkness that followed. The ground shook. Powerful gusts roiled the atmosphere. Debris rained from the sky. Soot and dust, spewed by the impact and resulting wildfires, filled the sky. That soot and dust then began to spread like a giant sunlight-blocking shade over the entire planet.
How long did the darkness last? Some scientists had estimated that it was anywhere from a few months to years. The resulting darkness could have lasted for months, possibly years. Many dinosaurs would have died within weeks.
The carnivores who feasted on the herbivores would have died a month or two later. Overall, the loss of biodiversity would have been tremendous. Only small scavenging mammals that could burrow into the ground and eat whatever remained would have survived. The iridium layer plus the Chicxulub Crater were evidence enough to convince many scientists that the bolide impact theory was credible.
It explained much of what previous theories could not. Paleontology remains a competitive discipline even though its central mystery appears to have been solved. Agreement over dinosaur extinction is far from unanimous, and fossils continue to be found that add to the body of knowledge about how the dinosaurs lived and died. Only recently have birds been identified as descendants of the dinosaurs, and theories regarding dinosaur intelligence and behavior continue to change.
The climate change theory still holds sway over some scientists, who refute that the Chicxulub impact was the sole cause of the extinction. Evidence from the million-year-old lava flows in India hint that a giant, gaseous volcanic plume might have initiated global climate change that threatened the dinosaurs.
But if you see something that doesn't look right, click here to contact us! Subscribe for fascinating stories connecting the past to the present. The prehistoric reptiles known as dinosaurs arose during the Middle to Late Triassic Period of the Mesozoic Era, some million years ago.
As part of the study, which appeared in the Proceedings of the National Academy of Science PNAS , an international team of scientists re-examined previously tested animal fossils from Neanderthal-era sites in southern Iberia modern-day Spain , a region believed to have been one Neanderthals are an extinct species of hominids that were the closest relatives to modern human beings.
They lived throughout Europe and parts of Asia from about , until about 40, years ago, and they were adept at hunting large, Ice Age animals. And, like their demise, their origins and heyday were triggered by huge, catastrophic mass extinctions.
At the end of the Permian period million years ago, more than 90 per cent of all life suddenly disappeared. The cause or causes of the wipeout is angrily debated, but there is no doubt about its devastating impact.
Life itself nearly went extinct, leaving bleak and empty landscapes over the vast single continent of Pangaea. A few plants and large land animals somehow clung on, and over the next 50 million years they gradually refilled the empty planet with life. The first to take advantage was a group of mammal-like reptiles called the synapsids.
They dominated the Early Triassic, and gave rise to mammals. By the middle of the Triassic period a second group of reptilian Permian survivors called the diapsids were starting to take over. Another lot evolved into snakes and lizards. The classic view is that archosaurs evolved in the Middle Triassic and quickly gave rise to crocodiles, dinosaurs and the flying pterosaurs.
Almost as soon as dinosaurs evolved, they started throwing their weight around. Or was it? This rare peek inside the guts of the crater showed that the impact would have been powerful enough to send deadly amounts of vaporized rock and gases into the atmosphere, and that the effects would have persisted for years. And in , paleontologists digging in North Dakota found a treasure trove of fossils extremely close to the K-Pg boundary , essentially capturing the remains of an entire ecosystem that existed shortly before the mass extinction.
Tellingly, the fossil-bearing layers contain loads of tiny glass bits called tektites—likely blobs of melted rock kicked up by the impact that solidified in the atmosphere and then rained down over Earth. However, other scientists maintain that the evidence for a massive meteor impact event is inconclusive, and that the more likely culprit may be Earth itself. Ancient lava flows in India known as the Deccan Traps also seem to match nicely in time with the end of the Cretaceous, with massive outpourings of lava spewing forth between 60 and 65 million years ago.
Today, the resulting volcanic rock covers nearly , square miles in layers that are in places more than 6, feet thick. Proponents of this theory point to multiple clues that suggest volcanism is a better fit. Other research has found evidence for mass die-offs much earlier than 66 million years ago, with some signs that dinosaurs in particular were already in a slow decline in the late Cretaceous.
This all makes sense, supporters say, if ongoing volcanic eruptions were the root cause of the world-wide K-Pg extinctions. Increasingly, scientists trying to unravel this prehistoric mystery are seeing room for a combination of these ideas. This nearly whole, deep-black skull belongs to the most complete specimen of Tyrannosaurus rex on display in Europe, an individual nicknamed Tristan Otto.
But that notion depends a lot on more precise dating of the Deccan Traps and the Chicxulub crater. This debate may rage for years, as scientists dig up new clues and develop new techniques for understanding the past. All rights reserved.
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