More than 99% of all living organisms on Earth are now extinct. Most of them died quietly. However, the history of the Earth has five main The mass Extinction events – known as Big five – During which many species became extinct at the same time.
Each of the five major events caused at least 40% loss of all species on Earth. Yet humans hold a particular grudge against the most recent one, which brought a sudden end to the 160 million-year history of dinosaurs. It was the Cretaceous – Paleogene extinction, and it occurred 66 million years ago, at that time wiping out about 75% of all species on Earth. Except for sea turtles and crocodiles, no four-legged animal larger than 25 kg survived.
After decades of heated debate, scientists have compromised on two major theories about the cause of this extinction. First possibility Effect of an asteroid That created the 180-km-wide Chicxulub impact crater in the modern-day Yucatán Peninsula in Mexico. Second, a series of eruptions in the volcanic region known as Deccan Trap in India.
Last week, an international team of scientists with data from four independent laboratories Published a study Claiming ended the debate. They say that the 12 km wide asteroid was to blame.
A Case Closed?
The study looked at rock samples collected in the pit, which is now underwater. They found a layer of terrestrial soil mixed with “space dust” containing the element iridium, which can be found in high concentrations in meteorites but is rare in the Earth’s crust. This layer was four times thicker in the impact crater than the surrounding area.
The team quickly found a 5-cm layer of sediment beneath the limestone from the Paleogene, a geological period that began shortly after extinction. This thin layer of sediment had an iridium concentration of one part per billion compared to 0.04 parts in the earth’s crust.
The asteroid is believed to have hit the planet faster than the speed of sound in the air at about 20 km per second, more than 50 times. This not only destroyed the immediate surroundings, but it sent a cloud of vaporized rock and microscopic dust with high levels of iridium that traveled to Earth. The global blanket of clouds blocked sunlight, cooled the Earth’s surface by 10 ° C for decades, and triggered a global “impact winter”. Large-scale photosynthesis ceased following the cold and dark regime, causing worldwide food disturbances and ecosystem collapse.
Iridium spikes have been found in the dust since this time More than 100 places From around the world to America, Asia, Europe, Oceania, Antarctica. They were first identified Findings from the 1980s.
Preliminary studies did not win global consensus because evidence could not add to the high iridium concentrations of the irritant crater. But this new study provides this important link, and also imposes an important time constraint. Dust should be collected within a few decades after impact – less than 20 years.
Dinosaur Armageddon
Although the nature of this extinction is supported by changes in the fossil record, the microbe record instead points towards a long-term shift. This is an argument in favor of a volcanic extinction, with a series of eruptions occurring over tens of thousands of years.
Large-scale and prolonged volcanic eruptions have been linked to other volcanic-extinction events – such as the Siberian trap eruption, which marked extinction at present End of permacion Period. In the case of the extinction event of the dinosaurs, however, this could not have been caused by the volcano alone.
The Deccan Trap released more than ten million cubic kilometers of material and gases, causing prolonged global warming between 2 and 4 ° C, 150 to 300 thousand years before extinction, Before the asteroid flick.
The Deccan Trap eruption, which began long before the asteroid impact, lasted several million years. In fact, about 66 million years ago, the main phase of the Deccan Traps volcano, may be Triggered by chicxulub effect.
Increased nutrient levels in the oceans Plankton blooms and low oxygen levels in the oceans, Yet the oceans were not completely oxygen free. The Deccan volcano may have stressed the creatures, but the creatures have not died completely.
Dinosaurs in the unfortunate dual trouble of an asteroid volcano combo, or a huge impact, can determine their doomsday. Either way, the large asteroid has played an important role. This new study revealed the missing piece of evidence that linked the extinction of dinosaurs to the Chixkulb effect, and it occurred in the geological blink of an eye.
By this article Rani Hoi Shan Chan, Lecturer in Earth Sciences, Royal Holloway Republished from chit chat Under a Creative Commons license. read the Original article.