Its lava volume could cover the continental U. The uptick in CO 2 acidified the Triassic oceans, making it more difficult for marine creatures to build their shells from calcium carbonate. On land, the dominant vertebrates had been the crocodilians, which were bigger and far more diverse than they are today. Many of them died out.
In their wake, the earliest dinosaurs—small, nimble creatures on the ecological periphery—rapidly diversified. The Cretaceous-Paleogene extinction event is the most recent mass extinction and the only one definitively connected to a major asteroid impact. Some 76 percent of all species on the planet, including all nonavian dinosaurs , went extinct. One day about 66 million years ago, an asteroid roughly 7. The massive impact—which left a crater more than miles wide—flung huge volumes of dust, debris, and sulfur into the atmosphere, bringing on severe global cooling.
Wildfires ignited any land within miles of the impact, and a huge tsunami rippled outward from the impact. Overnight, the ecosystems that supported nonavian dinosaurs began to collapse. Global warming fueled by volcanic eruptions at the Deccan Flats in India may have aggravated the event. Some scientists even argue that some of the Deccan Flats eruptions could have been triggered by the impact.
Earth is currently experiencing a biodiversity crisis. Recent estimates suggest that extinction threatens up to a million species of plants and animals , in large part because of human activities such as deforestation, hunting, and overfishing. Other serious threats include the spread of invasive species and diseases from human trade, as well as pollution and human-caused climate change.
Explore National Geographic magazine's special issue on extinction. Today, extinctions are occurring hundreds of times faster than they would naturally. If all species currently designated as critically endangered, endangered, or vulnerable go extinct in the next century, and if that rate of extinction continues without slowing down, we could approach the level of a mass extinction in as soon as to years. Climate change presents a long-term threat.
By total volume, these past volcanoes emitted far more than humans do today; the Siberian Traps released more than 1, times the CO 2 than humans did in from burning fossil fuels for energy. As mass extinctions show us, sudden climate change can be profoundly disruptive.
Well before hitting that grim marker, the damage would throw the ecosystems we call home into chaos, jeopardizing species around the world—including us. All rights reserved. Edaphosaurus A sail-backed edaphosaurus forages amid a Permian landscape in this artist's depiction.
Fleeing Nothosaurs An artist's rendering shows hatchling nothosaurs heading for the safety of water as a hungry but terrestrial Ticinosuchus attacks near a lagoon in ancient Switzerland. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city.
Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars. India bets its energy future on solar—in ways both small and big. Environment Planet Possible India bets its energy future on solar—in ways both small and big Grassroots efforts are bringing solar panels to rural villages without electricity, while massive solar arrays are being built across the country.
Go Further. Animals Climate change is shrinking many Amazonian birds. Animals Wild Cities This wild African cat has adapted to life in a big city.
Animals This frog mysteriously re-evolved a full set of teeth. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs. The anoxic oxygen-lacking waters could have spilled onto the continental shelves, the high carbon dioxide content, toxic to marine life, poisoning much of the life in the oceans.
At the same time, massive outpourings of volcanic basalt rock in what is now Siberia added huge amounts of heat, carbon dioxide, and sulfur dioxide to Earth's surface and atmosphere. The carbon dioxide could have trapped heat in the atmosphere, and the resulting "greenhouse effect" generated a long warming trend.
The climate change triggered by the warming could have shifted weather patterns dramatically, so that regions normally wet and rainy became dry and vice versa. Geologic evidence supporting this hypothesis has been found in recent investigations in the Caledon River in South Africa.
Did all these factors -- sea-level change, climate change, ocean stagnation, carbon dioxide buildup -- combine to cause the Great Dying? We don't have all the answers. And, in fact, in a group of scientists uncovered evidence suggesting that an asteroid may have hit Earth at the end of the Permian era, further complicating the picture. The evidence is still circumstantial, however, and what role, if any, an impact may have played is unclear.
Scientists continue to examine the evidence for clues to the cause of the Permian-Triassic extinction. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most.
Please support us by making a donation or purchasing a subscription today. Credit: Victor O Leshyk. More on:. The Triassic was marked with small carnivorous dinosaurs that walked on two legs.
Lauren Fuge Lauren Fuge is a science journalist at Cosmos. More from:. Lauren Fuge. Read science facts, not fiction
0コメント