Years after the asteroid collision that wiped out non-birds dinosaur It was a dark time — literally. New research has found that soot from raging wildfires fills the sky, blocks the sun, and contributes directly to the subsequent waves of extinction.
About 66 million years ago, after the asteroids collided, cataclysms immediately extinguished many forms of life. However, the effects also caused changes in the environment, causing mass extinction over time. One of the triggers for such extinction could have been a dense cloud of ash and particles that erupted into the atmosphere and spread throughout the planet.
in the meantime photosynthesis It will fail and lead to the collapse of the ecosystem. The decline could continue for decades even after sunlight returns, according to a study released December 16 at the American Geophysical Union (AGU) Annual Meeting in New Orleans and online. there is.
The Cretaceous It ended with great success when an asteroid moving at about 27,000 mph (43,000 km / h) collided with the Earth (145-66 million years ago). Approximately 7.5 miles (12 km) in diameter, underwater in the Gulf of Mexico near the Yucatan Peninsula, it left at least 90 miles (150 km) of scars called the Chicxulub Crater. The impact eventually wiped out at least 75% of life on Earth, including all non-avian dinosaurs (the lineage that gave birth to modern birds is the only branch of the dinosaur family tree that survived extinction).
Crushed rocks and clouds of sulfuric acid from the crash would have darkened the sky, lowered the temperature of the earth, caused acid rain, and caused wildfires. Live science previously reported..Scientists first suggested a postasteroid “Nuclear winter scenario” in the 1980s. This hypothesis suggests that darkness is involved in the post-Cretaceous mass extinction, a curator of invertebrate zoology and geology at the California Academy of Sciences, and a curator of the AGU Conference. Presenter Peter Roopnarine said.
But researchers have developed a model of how that darkness has affected life in the last decade or so, Roopnarine told Live Science in an email.
“The current general belief is that global wildfires would have been the main source of fine soot that would have been floating in the upper atmosphere,” Roopnarine said. “Within the first few days to weeks of the fire, the concentration of soot would have been high enough to reduce the amount of incident sunlight to levels low enough to prevent photosynthesis.”
Long-term darkness by reconstructing the ecological community that would have existed at the time of the asteroid collision. They used 300 species known from the Hell Creek Formation, a fossil-rich spread of shale and sandstone that dates back to the late Cretaceous and spans parts of Montana, North Dakota, South Dakota, and Wyoming. ..
“Because the fossil records are well sampled and ecologically well understood, we focused on the area, which ensured a restructuring of the paleo-community,” Roopnarine said. Said.
Next, they created a simulation that exposed the community to a period of darkness that lasted between 100 and 700 days to see which intervals produced the vertebrate extinction rate (about 73%) stored in fossil records. did. The onset of darkness after the shock was rapid and reached its maximum in just a few weeks, Roopnarine said in an email.
Researchers have discovered that ecosystems can recover after periods of darkness that last up to 150 days. But 200 days later, scientists reported that the same community had reached a critical turning point: “some species have become extinct and the pattern of dominance has changed.” In simulations where darkness lasted the longest, extinction surged dramatically. According to the model, the extinction level reached 65% -81% between 650-700 days of darkness, suggesting that the Hell Creek community experienced about two years of darkness.
“Although changes in atmospheric flow and temperature have changed the situation around the world, it has been estimated that darkness can continue for up to two years in the Hell Creek region,” Roopnarine said. The results are preliminary and
When the ecosystem reaches its turning point, it may eventually recover with a new species distribution. But researchers have found that the process will take decades. The long-term stimulus of the 700-day darkened Hell Creek community showed that it took 40 years for the ecosystem to begin to recover after the darkness was lifted, scientists reported at the conference. ..
Originally published on Live Science.
The darkness caused by the asteroids that kill dinosaurs has wiped out life on Earth in nine months.
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