Source: Xinhua Net
Nanjing, Jan. 20 (Xinhua) -- 200 million years ago, a mass extinction wiped out more than half of the earth's creatures. Where did this "catastrophe" in evolutionary history come about? Recently, an international team led by China University of Geosciences (Wuhan) and the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences found strong evidence that volcanic eruptions were the main cause of environmental upheaval and species extinction at that time. The relevant results have been published in the international authoritative journal Nature Communications recently.
Schematic of a volcanic eruption leading to a forest fire 200 million years ago. Painted by Yang Dinghua, Institute of Southern Antiquities, Chinese Academy of Sciences
Wang Yongdong, a researcher at the Institute of Southern Antiquities of the Chinese Academy of Sciences who participated in the study, introduced that the Triassic-Jurassic intersection mass extinction 200 million years ago was one of the five biological mass extinctions in the history of the earth. For decades, scientists have speculated about the cause of the extinction, and the eruption is considered an important trigger, but the extent of its impact has been difficult to determine.
This time, the scientific research team conducted research on carbon isotopes, mercury elements, clay minerals and so on in two different latitude strata during this period. The results showed a marked increase in mercury levels in these formations, fluctuations in carbon isotope values, and changes in clay minerals indicating weathering. Since volcanic activity is the most important natural source of mercury in geological history, the results prove that volcanic eruptions not only spread widely, but also led to a series of climatic and ecological upheavals.
Stratigraphic profiles involved in this study: photos of Haojiagou profile in The Junggar Basin of Xinjiang. Photo courtesy of China University of Geosciences (Wuhan).
Stratigraphic profiles involved in this study: Xuanhan profile photos of The Sichuan Basin. Photo courtesy of the Nangu Institute of the Chinese Academy of Sciences
Combined with previous geological research, researchers have roughly reconstructed the scene of mass extinction 200 million years ago: when a "supervolcano" on land continued to erupt for nearly 600,000 years, forming a large-scale magmatic deposit across North America and Pangea. Volcanoes emit huge amounts of carbon dioxide and methane gas into the atmosphere, bringing carbon dioxide concentrations to about 10 times higher than they do now. Increasing greenhouse gases are causing warming, ocean hypoxia, acidification of seawater and increasing continental weathering. This process lasted about 2 million years. A large number of creatures could not adapt to the upheaval of the environment and eventually disappeared from the earth.
"However, this mass extinction also provides room for other organisms to develop." Soon after, dinosaurs appeared, beginning their 100 million-year-long journey of domination. Shen Jun, the first author of the paper and a researcher at China University of Geosciences (Wuhan), said.