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While people are still thrilled by scenes of the destruction of the Earth in the movie 2012, scientists are finding ways to explain the reasons for past extinctions, which can serve as a warning for the human race.
The end-Permian mass extinction, about 252.28 million years ago, was the most severe biodiversity crisis in the Earth’s history. The Permian is a geologic period and system which extends from approximately 299 million to 251 million years ago.
A Paleozoic research group led by Shen Shuzhong from Nanjing Institute of Geology and Paleontology (NIGP) found out that in the end-Permian, 80-95 percent of all species on Earth, on land and in the oceans, became extinct within an estimated time interval of less than 200,000 years.
The process was much shorter than the previous judgment, which was 10 million years, made by John Sepkoski in 1984. Sepkoski was a renowned paleontologist of the University of Chicago in the United States.
The research result said the course of environmental deterioration can last for a long time. Once the deterioration accumulates beyond the capacity of the ecosystem, mass extinction can occur quickly in a very short period of time.
The end-Permian extinction is the worst of its kind in the Earth’s history. The whole ecosystem collapsed and the biosphere almost went back to its original state. Following that, the Earth entered a 5-million-year slump of biological activity.
The new findings come from 10 years’ arduous work by an international research team made up of 14 institutions across the world, including NIGP under the Chinese Academy of Sciences, the University of Science and Technology of China and the Massachusetts Institute of Technology.
The team had more than 20 scientists from across the world and was led by Chinese scientist Shen Shuzhong, a researcher with the NIGP. Their paper, titled “Calibrating the End-Permian Mass Extinction,” was published in Science, a top academic magazine.
It was difficult to determine the exact period of the mass extinction. And the reasons for the extinction had long been a mystery, said Shen.
As early as 2000, a group of Chinese scientists led by Jin Yugan, an expert on stratigraphic paleontology and former director of the academic committee of NIGP, published a paper in Science. They theorized the mass extinction was caused by an instantaneous event instead of gradual extinction.
This assumption challenged Darwin’s theory of evolution featuring survival of the fittest. But it was echoed by a group of U.S. and Japanese scientists. They said that an asteroid slammed into the Earth and the strong seismic waves instantly killed almost all living creatures. Their opinions were popular for a long time.
The evidence
To determine the nature of the mass destruction required finding enough fossils, which are the most accurate record of evolution. So Shen led his research team to collect fossils in mountains and remote areas, looking for evidence from hundreds of millions of years ago.
Over the past decade, Shen’s team went across China, went to Pakistan and surrounding areas. They conducted high-resolution biostratigraphy into the geological profiles of the Permian-Triassic times in these areas. These geological profiles included the marine environment, terrestrial environment and transitional environment between the two.
Their efforts proved fruitful. In Meishan Mountain in east China’s Zhejiang Province, they found a high-resolution tooth-shaped fossil zone. The fossils varied in size, but were all similar rectangles. They were standard fossils that paleontologists use to divide the Paleozoic and the Mesozoic eras.
They also found traces of volcanic ash. After each volcanic eruption, the ash would be deposited and stored in the ground. According to Shen, the volcanic ash often contained zircon and other minerals. These minerals are very stable and can withstand temperatures as high as 3,000 degrees Centigrade. They are common in acid igneous rocks. Their composition can be used to determine the exact time of a volcanic eruption.
Paleontologists collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections. High-precision zircon U-Pb dating reveals that the extinction peak occurred just before 252.28 million years ago minus or plus 80,000 million years ago.
It was the first time the scientific community determined the exact time of the mass destruction.
“The 25th layer of the geological profile in Meishan Mountain was crucial. It was the exact layer of volcanic ash which dated back 252.28 million years,” said Shen.
“After fossil comparison, volcanic ash age analysis, as well as other scientific means, we got the exact time of the mass extinction. Our result shortened the previous estimated period of the mass extinction to 200,000 years. Thus we proved the mass destruction was absolutely not a slow process but a quick and short one,” said Shen.
During the process of collecting evidence and doing research, the team noticed an extraordinary change in the carbon isotope. The carbon isotope ratio is an effective means of determining the source of the carbon dioxide in the atmosphere. The team discovered within the short period of 10,000 to 20,000 years at end-Permian period, the Earth’s inorganic carbon isotopic concentrations witnessed a sharp fluctuation.
“Such a dramatic fluctuation means a quick change in the percentage of carbon dioxide in the atmosphere. It indicates the advent of a disaster for global biodiversity,”said Shen.
Reasoning
As Shen saw it, at the end-Permian period, underground magma became active. Its largescale movement led to the release of methane and volcanic eruptions.
As a result, carbon dioxide increased quickly and the greenhouse effect intensified. The lack of oxygen in the sea led to a mass extinction of marine life. In the meantime, it quickly got warm and dry on the Earth. This caused widespread wildfires, which eventually triggered the catastrophic extinction.
This was proved by the plant fossils. The team found a lot of evidence of burning trees in the fossils. The continuous burning of trees led to vast disappearance of forests. And the soil protection system collapsed.
Before Shen’s discovery, it was generally agreed among academics that the process of mass extinction at the end-Permian period began with the sea and then spread to the land. But Shen’s research showed the sea and the land suffered from the quick and devastating hit at almost the same time.
The release of methane, volcanic eruptions, increase in carbon dioxide and greenhouse effect had a synchronous impact on the marine and terrestrial ecosystems synchronously, said Shen.
This was also proved by the fossils. The team found fossils of gigantopterides, a representative rainforest plant, in the equatorial regions. They showed rainforest plants disappeared simultaneously with marine life. It took the Earth more than 5 million years to recover, said Wang Jun, another researcher with the NIGP.
“The mass extinction at end-Permian told us the ecosystem’s reactions to the environmental degradation may be long-term, but once the pressure on the environment goes beyond the capacity of the ecosystem, it can collapse in a very short time,” said Shen.
“Human beings therefore should cherish the current environment,” he said.
The end-Permian mass extinction, about 252.28 million years ago, was the most severe biodiversity crisis in the Earth’s history. The Permian is a geologic period and system which extends from approximately 299 million to 251 million years ago.
A Paleozoic research group led by Shen Shuzhong from Nanjing Institute of Geology and Paleontology (NIGP) found out that in the end-Permian, 80-95 percent of all species on Earth, on land and in the oceans, became extinct within an estimated time interval of less than 200,000 years.
The process was much shorter than the previous judgment, which was 10 million years, made by John Sepkoski in 1984. Sepkoski was a renowned paleontologist of the University of Chicago in the United States.
The research result said the course of environmental deterioration can last for a long time. Once the deterioration accumulates beyond the capacity of the ecosystem, mass extinction can occur quickly in a very short period of time.
The end-Permian extinction is the worst of its kind in the Earth’s history. The whole ecosystem collapsed and the biosphere almost went back to its original state. Following that, the Earth entered a 5-million-year slump of biological activity.
The new findings come from 10 years’ arduous work by an international research team made up of 14 institutions across the world, including NIGP under the Chinese Academy of Sciences, the University of Science and Technology of China and the Massachusetts Institute of Technology.
The team had more than 20 scientists from across the world and was led by Chinese scientist Shen Shuzhong, a researcher with the NIGP. Their paper, titled “Calibrating the End-Permian Mass Extinction,” was published in Science, a top academic magazine.
It was difficult to determine the exact period of the mass extinction. And the reasons for the extinction had long been a mystery, said Shen.
As early as 2000, a group of Chinese scientists led by Jin Yugan, an expert on stratigraphic paleontology and former director of the academic committee of NIGP, published a paper in Science. They theorized the mass extinction was caused by an instantaneous event instead of gradual extinction.
This assumption challenged Darwin’s theory of evolution featuring survival of the fittest. But it was echoed by a group of U.S. and Japanese scientists. They said that an asteroid slammed into the Earth and the strong seismic waves instantly killed almost all living creatures. Their opinions were popular for a long time.
The evidence
To determine the nature of the mass destruction required finding enough fossils, which are the most accurate record of evolution. So Shen led his research team to collect fossils in mountains and remote areas, looking for evidence from hundreds of millions of years ago.
Over the past decade, Shen’s team went across China, went to Pakistan and surrounding areas. They conducted high-resolution biostratigraphy into the geological profiles of the Permian-Triassic times in these areas. These geological profiles included the marine environment, terrestrial environment and transitional environment between the two.
Their efforts proved fruitful. In Meishan Mountain in east China’s Zhejiang Province, they found a high-resolution tooth-shaped fossil zone. The fossils varied in size, but were all similar rectangles. They were standard fossils that paleontologists use to divide the Paleozoic and the Mesozoic eras.
They also found traces of volcanic ash. After each volcanic eruption, the ash would be deposited and stored in the ground. According to Shen, the volcanic ash often contained zircon and other minerals. These minerals are very stable and can withstand temperatures as high as 3,000 degrees Centigrade. They are common in acid igneous rocks. Their composition can be used to determine the exact time of a volcanic eruption.
Paleontologists collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections. High-precision zircon U-Pb dating reveals that the extinction peak occurred just before 252.28 million years ago minus or plus 80,000 million years ago.
It was the first time the scientific community determined the exact time of the mass destruction.
“The 25th layer of the geological profile in Meishan Mountain was crucial. It was the exact layer of volcanic ash which dated back 252.28 million years,” said Shen.
“After fossil comparison, volcanic ash age analysis, as well as other scientific means, we got the exact time of the mass extinction. Our result shortened the previous estimated period of the mass extinction to 200,000 years. Thus we proved the mass destruction was absolutely not a slow process but a quick and short one,” said Shen.
During the process of collecting evidence and doing research, the team noticed an extraordinary change in the carbon isotope. The carbon isotope ratio is an effective means of determining the source of the carbon dioxide in the atmosphere. The team discovered within the short period of 10,000 to 20,000 years at end-Permian period, the Earth’s inorganic carbon isotopic concentrations witnessed a sharp fluctuation.
“Such a dramatic fluctuation means a quick change in the percentage of carbon dioxide in the atmosphere. It indicates the advent of a disaster for global biodiversity,”said Shen.
Reasoning
As Shen saw it, at the end-Permian period, underground magma became active. Its largescale movement led to the release of methane and volcanic eruptions.
As a result, carbon dioxide increased quickly and the greenhouse effect intensified. The lack of oxygen in the sea led to a mass extinction of marine life. In the meantime, it quickly got warm and dry on the Earth. This caused widespread wildfires, which eventually triggered the catastrophic extinction.
This was proved by the plant fossils. The team found a lot of evidence of burning trees in the fossils. The continuous burning of trees led to vast disappearance of forests. And the soil protection system collapsed.
Before Shen’s discovery, it was generally agreed among academics that the process of mass extinction at the end-Permian period began with the sea and then spread to the land. But Shen’s research showed the sea and the land suffered from the quick and devastating hit at almost the same time.
The release of methane, volcanic eruptions, increase in carbon dioxide and greenhouse effect had a synchronous impact on the marine and terrestrial ecosystems synchronously, said Shen.
This was also proved by the fossils. The team found fossils of gigantopterides, a representative rainforest plant, in the equatorial regions. They showed rainforest plants disappeared simultaneously with marine life. It took the Earth more than 5 million years to recover, said Wang Jun, another researcher with the NIGP.
“The mass extinction at end-Permian told us the ecosystem’s reactions to the environmental degradation may be long-term, but once the pressure on the environment goes beyond the capacity of the ecosystem, it can collapse in a very short time,” said Shen.
“Human beings therefore should cherish the current environment,” he said.