DATE2022.01.13 #Press Releases

Did Global Cooling Caused by Volcanic Activity Lead to Dinosaurs' Prosperity? Clarifying the reality of the mass extinction at the end of the Triassic Period

Disclaimer: machine translated by DeepL which may contain errors.

Graduate School of Science, Tohoku University

Yamaguchi University

The University of Tokyo, Graduate School of Science

Summary

The fourth of the five major mass extinctions, the end-Triassic mass extinction about 200 million years ago, marked the extinction of large reptiles, ancestors of crocodilians, which had thrived until then, and the beginning of the diversification of dinosaurs (Figure). The Triassic dinosaurs, which had been small and unassuming until then, rapidly increased in size after the mass extinction at the end of the Triassic period, leading to their prosperity from the Jurassic period onward.

The cause of this mass extinction was thought to be large-scale volcanic activity that caused the breakup of the supercontinent Pangaea. However, it was unclear how the volcanic activity caused the environmental change.

Professor Kunio Kaiho (now Emeritus Professor at Tohoku University) and his research group conducted heating experiments on sedimentary rocks and found that sulfur dioxide is released at relatively low temperatures and carbon dioxide is released more at higher temperatures. Furthermore, they inferred that volcanic activity shifted from low to high temperatures based on changes in the types of sedimentary organic molecules produced under controlled heating temperatures found in strata that record mass extinctions. Based on these results, we proposed that the mass extinction at the end of the Triassic period occurred through the following process (Figure):
Magma from large-scale volcanic activity heated sedimentary rocks at relatively low temperatures, resulting in the formation of large amounts of sulfur dioxide.
The sulfur dioxide entered the stratosphere and formed sulfuric acid aerosols.
The sulfuric acid aerosol reflected sunlight and caused the mass extinction of organisms due to photosynthesis inhibition and global cooling.

The results of this research were published in the January 12 electronic edition of the international journal Earth and Planetary Science Letters prior to its publication. It was deemed important by the editors and was published extra-early.

Figure: Causes of the end-Triassic mass extinction: global cooling caused the extinction of large reptiles of crocodilian ancestry, while dinosaurs survived, grew larger, and reigned at the top of the ecosystem. Large volcanic areas are in the Central Atlantic region. (©️Kunio Kaiho)

Associate Professor Masayuki Ikeda and Assistant Professor Satoshi Takahashi of the Department of Earth and Planetary Science and Assistant Professor Ryosuke Saito of Yamaguchi University (formerly Project Assistant Professor, Department of Earth and Planetary Science) participated in this research.

For more information, please visit the website of Graduate School and Faculty of Science, Tohoku University.