At the end of the Permian, marine life suffered the worst blow ever, with more than 80% of marine life and most terrestrial life extinct. Celestial impact, climate warming, volcanic eruption ...
Looking back on the geological history, there have been five major biological extinction events on the earth. These events caused at least 75% of the species in the ocean to be extinct in a short time. Until today, after years of research, scientists from various countries have made various hypotheses, but they have disputes over the causes of the mass extinction.
The Science and Technology Daily reporter recently learned from the Nanjing Institute of Geology and Paleontology, the Chinese Academy of Sciences that the research team of the institute has collaborated with American scholars to carry out research on the largest extinction of marine life in the history of the earth. At the end of the Permian 250 million years ago, an unprecedented mass extinction caused more than 80% of marine life and most terrestrial life to perish. This is the worst blow to marine life in history.
More than ten years ago, the scientific research team of the Institute of Geology and Palaeontology of the Chinese Academy of Sciences carried out scientific drilling and sampling work on a section of the stratum that spanned the Permian-Triassic transition period in Meishan, Changxing County, Zhejiang Province. There may be hidden traces of the "culprit" of the extinction.
What caused the extinction of marine life at the end of the Permian? Is it a celestial collision, ocean acidification, or global warming? What are the reasons for the other mass extinctions? Will this mysterious "killer" appear again and stage the sixth biological extinction? The reporter interviewed Zhang Hua, a researcher at the Nanjing Institute of Geology and Palaeontology, who led the research, with questions.
The worst biological extinction in history
So far, there have been 5 very large extinction events in the history of the earth. Among them, the biological extinction at the end of the Permian period is undoubtedly recognized as a serious extinction event during the geological history.
In the past, due to the coarse statistical scale, the Permian biological extinction was thought to have occurred over a long period of time (about 10 million years).
Later, after further research, scientists discovered that the Permian biological extinction was divided into two stages: one occurred at the end of Guadalupe (about 260 million years ago), which may be related to the large-scale eruption of the Emeishan basalt at that time; another Occurred at the end of the Permian (about 250 million years ago). "Currently commonly referred to as the end of the Permian biological extinction refers to the biological extinction event occurred at the turn of the Permian-Triassic." Zhang Hua said.
The well-known trilobite was a relatively common creature at that time, and its fossils could be excavated in many parts of China. In the ocean 500 million years ago, trilobites once occupied the dominant position, which can be called the hegemon in the sea. But in this mass extinction, the trilobite disappeared completely and never appeared again.
Not only trilobites, this mass extinction caused the extinction or drastic reduction of many major categories in the very prosperous fauna of the Paleozoic. For example, the four-shot coral, horizontal plate coral, sea buds, etc. have all suffered from the extinction of the top, and they have disappeared from now on; there are also brachiopods in the late Paleozoic, which were obviously miniaturized at the level of the mass extinction. , Shi Yanmu and Straight Shellfish are extinct.
At the same time, the terrestrial ecosystem of the earth also suffered a major blow. According to Zhang Hua, the continent of the earth at that time was completely different from the present. The plate movement of hundreds of millions of years, in the Permian era, the main continents of the world joined together to become a super-continent called "Pangulu". On the vast land, many plants and animals have been nourished, such as the tropical rain forest flora represented by the large feather fern in southern China, and the vertebrate two-toothed beast that dominated the late Permian.
However, in this unprecedented mass extinction, the tropical rainforest flora represented by large feathered fern teeth basically disappeared, and the vertebrate community represented by two-toothed beasts also suffered a major blow, and the number decreased sharply.
Zhang Hua told reporters that paleontologists conducted statistics based on fossil records, and about 95% of marine life species and about 75% of terrestrial life species were extinct.
The apparent lack of oxygen in the ocean causes organisms to "suffocate"
In the nearly 300 million years after the Cambrian life broke out, the land and sea on the surface of the earth constantly changed, and life continued to escalate. Every era is a new stage, and every era has a new "actor".
At the same time, a large number of species have been eliminated, including those who are incapable of life. So, who controls the reincarnation of life on earth?
According to Zhang Hua, the end of the Permian biological extinction is the most serious event in the history of the earth. If you can find out the exact cause, it will help to uncover the veil of several other biological extinctions. There are many speculations about the reason, and the most popular is the volcanic eruption.
Some scholars have also suggested that the impact of celestial bodies caused the biological extinction of the end of the Permian. The impact of extraterrestrial asteroids or comets on the earth will definitely have catastrophic consequences. , Trigger a giant tsunami in the ocean. However, this view is not supported by sufficient evidence and has been questioned by many parties.
The view of volcanic eruptions is even more convincing. As the saying goes, points must be together and points together. The earth continents did not stop moving after being spliced together by plate movement. The powerful forces inside the earth pushed the plates to squeeze each other, causing large-scale volcanic eruptions. The pan-continent gradually split at the end of the Permian. In Siberia, Russia, there are still a lot of volcanic eruptions. Some people think that it was the largest volcanic eruption in the history of the earth, emitting a lot of greenhouse gases and minerals.
The research team led by Zhang Hua conducted a study on a section of the stratum in Changxing County, Zhejiang Province, and found that this section was once an ancient ocean, recording about 500,000 years of marine geological history before and after the mass extinction.
They analyzed elements such as iron, molybdenum, uranium, and vanadium that were very sensitive to redox in formation samples. The results showed that during the mass extinction, the ocean was in a state of hypoxia, and for some time after the end of the mass extinction, the situation of hypoxia had not changed significantly. In addition, sulfides common in anoxic environments were also found in formation samples.
"We compared other studies and found that before and after the mass extinction, there was a general lack of oxygen in the global ocean. We believe that it is likely that geological events such as volcanic eruptions at that time produced a large amount of reducing materials and imported them into the ocean. Oxygen in seawater It was consumed in large quantities, and general hypoxia appeared, and most of the marine organisms died in the end. "Zhang Hua said.
The sudden change of the global environment exists behind the scenes
At present, there are about 1.5 million species of creatures on earth. This number sounds very much, but it actually only accounts for 1% of the total species that the earth once possessed. In other words, 150 million creatures once lived on the planet, and now 99% of them are extinct.
The five biological extinctions that many species disappeared in the Phanerozoic occurred at the end of the Ordovician 430 million years ago, the late Devonian 370 million years ago, the end of the Permian 250 million years ago, and 200 million years. Before the end of the Triassic and the end of the Cretaceous 66 million years ago, the extinction of dinosaurs occurred at the end of the Cretaceous.
Scientists have listed no less than 20 possible causes of the destruction of the entire biosphere.
Zhang Hua told reporters that studies have shown that life has been continuously evolving since 600 million years, and no extraterrestrial events have destroyed the entire Earth ’s biosphere. All these biological mass extinction events are almost accompanied by dramatic global environmental changes.
These environmental and climate changes include the ice chamber effect or the greenhouse effect, and lead to dramatic changes in atmospheric temperature, ocean acidification and hypoxia, and marine microbial outbreaks, all of which indicate that dramatic climate and environmental changes are the cause of the mass extinction. .
"Behind the scenes, most of the black hands point to large-scale volcanic eruptions caused by internal activities on the earth." Zhang Hua said that even the public attention to the end of the Cretaceous biological mass extinction event has gradually been confirmed to be closely related to India's Deccan basalt eruption.
Therefore, experts believe that large-scale volcanic eruptions trigger the rapid release of greenhouse gases such as methane and carbon dioxide buried in the ground in a short period of time. When these greenhouse gases enter the atmosphere, they will cause dramatic changes in the surface environment, resulting in mass extinction.
Since human records, the Earth has not observed large-scale volcanic eruptions of thousands of square kilometers. However, humans have brought unprecedented changes to the earth ’s environment, causing a large amount of carbon dioxide to enter the atmosphere. If this trend continues for a long time, it is inevitable that the earth ’s biosphere will enter a new round of mass extinction.