The worst mass extinction in history was someone who "murdered" 80% of the creatures in the oceans

At the end of the Permian, marine life suffered the worst blow ever, with more than 80% of marine life and most of terrestrial life perishing. Celestial impacts, warming, volcanic eruptions...

Back in geological history, there have been five major extinction events on Earth, which caused at least 75% of the species in the oceans at that time to go extinct in a short period of time. Until today, after years of research, scientists from various countries have proposed a variety of hypotheses, but the cause of the mass extinction is controversial.

Science and Technology Daily reporter recently learned from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences that the research team of the Institute cooperated with American scholars to conduct research on the largest extinction of marine organisms in the history of the earth. At the end of the Permian, 250 million years ago, an unprecedented mass extinction wiped out more than 80 percent of marine life and most of terrestrial life. This is the worst blow ever suffered by marine life.

More than a decade ago, in a stratigraphic section of the Coal Mountain in Changxing County, Zhejiang Province, spanning the Permian-Triassic transition period, the scientific research team of the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences conducted scientific research drilling and sampling, and the core obtained this time may contain clues of the "culprit" of the mass extinction.

What exactly led to the mass extinction of marine life at the end of the Permian? Is it a celestial impact, ocean acidification or earth warming? What are the causes of other mass extinctions? Will this mysterious "killer" reappear and stage the sixth mass extinction? The reporter interviewed Zhang Hua, a researcher at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, who led the research with questions.

The worst mass extinction in history

So far, there have been 5 very large extinction events in the history of the Earth, of which the mass extinction at the end of the Permian is indisputably recognized as a serious extinction event in geological history.

In the past, due to the coarse statistical scale, permian mass extinctions were thought to have occurred over a long period of time (about 10 million years).

Later, after further research, scientists found that the Permian mass extinction was divided into two stages: one occurred at the end of the Guadarupu era (about 260 million years ago), which may be related to the large-scale eruption of the Emei Mountain basalt at that time; and the other occurred at the end of the Permian (about 250 million years ago). "At present, the so-called mass extinction at the end of the Permian refers to the extinction event that occurred at the turn of the Permian-Triassic period." 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, the trilobite once dominated, and it can be called the hegemon of the sea. But in this mass extinction, the trilobite disappeared completely and never reappeared.

Not only trilobites, but this mass extinction caused the extinction or drastic reduction of many major phyla in the very prosperous paleozoic fauna. For example, tetrafluorite corals, transverse corals, sea buds, etc. have all been wiped out and have since disappeared; there are also brachiopods in the late Paleozoic Era, which are significantly miniaturized in the mass extinction layer, and the once thriving long-bodied shellfish, twisted moon shellfish, stone swallows and straight shellfish are extinct.

At the same time, the Earth's terrestrial ecosystems have also suffered a major blow. According to Zhang Hua, the earth's continents at that time were completely different from today's, with hundreds of millions of years of plate movement, and in the Permian period, the major continents of the world were put together to become a supercontinent called "Pan-Paleontine". On the vast land, it nourishes many plants and animals, such as the tropical rainforest flora represented by the large feathered sheep's teeth in South China, and the vertebrate dipodonts that dominated in the late Permian.

However, in this unprecedented mass extinction, the tropical rainforest flora represented by the large feathered sheep's teeth has basically disappeared, and the vertebrate group represented by the diplodont has also suffered a major blow, and the number has decreased sharply.

Zhang Hua told reporters that paleontologists have calculated based on the fossil record that about 95% of marine biological species and about 75% of terrestrial biological species have been tragically extinct.

Significant lack of oxygen in the ocean causes organisms to "choke to death"

In the nearly 300 million years after the Cambrian explosion of life, the sea and land on the surface of the earth are constantly changing, life is constantly upgrading, each era is a new stage, and each era has a new "actor" on the stage.

At the same time, there are also a large number of species eliminated, including those who are invincible overlords. So, who exactly is ruling the cycle of life on Earth?

According to Zhang Hua, the end-Permian mass extinction is the most serious event in the history of the earth, if the exact cause can be found, it will help to unveil the veil of several other biological mass extinctions, there are many speculations about the cause of the mass extinction at the end of the Permian, and the more popular is the volcanic eruption.

Some scholars have also proposed that celestial impacts cause mass extinctions at the end of the Permian, and extraterrestrial asteroids or comets hitting the earth will definitely have catastrophic consequences, for example, it will cause the earth's magnetic poles to reverse, cause fires on land, and cause giant tsunamis in the ocean. However, this view is not supported by enough evidence and has been questioned by many parties.

The idea of a volcanic eruption is even more convincing. As the saying goes, if you divide for a long time, you will be united for a long time. After the Earth continents were spliced together by plate movements, they did not stop moving, and the powerful forces inside the Earth pushed the plates to squeeze each other, causing large-scale volcanic eruptions, and the Pan continent gradually split at the end of the Permian. In Siberia, Russia, there are still a large number of traces of volcanic eruptions. Some believe that it was the largest volcanic eruption in Earth's history, spewing out vast amounts of greenhouse gases and minerals.

A team led by Zhang Hua found that a section of stratigraphic stratigraphy in Changxing County, Zhejiang Province, was once an ancient ocean and recorded about 500,000 years of marine geological history before and after the mass extinction.

They analyzed elements such as iron, molybdenum, uranium, vanadium, etc. in formation samples that are very sensitive to redox. The results showed that the oceans were in a state of hypoxia during the mass extinction, and the hypoxia situation did not change significantly for some time after the end of the mass extinction. In addition, sulphides commonly found in hypoxic environments were found in formation samples.

"We compared other studies and found that around the time of the mass extinction, there was a general lack of oxygen in the world's oceans. We believe that it is likely that geological events such as volcanic eruptions at that time produced large amounts of reducing material and imported it into the ocean. Oxygen in the seawater is consumed in large quantities, and widespread hypoxia occurs, eventually most marine life dies. Zhang Hua said.

There is a culprit behind the mutation of the Earth's environment

At present, there are about 1.5 million species of living things on Earth. That number sounds like a lot, but it's only 1% of the total number of species the Earth once had. That is to say, the Earth was once inhabited by 150 million species of life, and today, 99% of them are extinct.

Many species disappeared from the five mass extinctions of the Phanerozoic, occurring 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, the end of the Triassic period 200 million years ago, and the end of the Cretaceous Period 66 million years ago.

Scientists have listed no less than 20 reasons that could cause the destruction of the entire biosphere.

Zhang Hua told reporters that studies have shown that life has been evolving continuously for 600 million years, and no extraterrestrial event has ever destroyed the entire earth's biosphere, and all these biological mass extinction events are almost accompanied by drastic global environmental changes.

These environments and climate changes, including the glacial or greenhouse effect, and lead to dramatic changes in atmospheric temperature, ocean acidification and hypoxia, and outbreaks of marine microorganisms, all of which indicate that drastic climatic and environmental changes are responsible for mass extinctions.

"Most of the people behind it point to massive volcanic eruptions caused by activity inside the Earth." Zhang Hua said that even the public attention of the end-Cretaceous mass extinction event has gradually been confirmed to be closely linked to the Deccan basalt eruption in India.

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, and these greenhouse gases enter the atmosphere to trigger drastic changes in the surface environment, resulting in mass extinction.

Since human records have been made, the Earth has not observed a large-scale volcanic eruption of thousands of square kilometers. However, human beings have brought unprecedented changes to the earth's environment, causing a large amount of carbon dioxide to enter the atmosphere, and if this trend is maintained for a long time, it is inevitable that the earth's biosphere will enter a new round of mass extinction.