Professor Kunio Kaiho of Tohoku University and Dr. David Jones of Amherst College in the United States have revealed that a large-scale volcanic eruption was the cause of the first mass extinction.
Of the five mass extinctions alleged to have occurred so far, the latter three are known to be the third and fourth large-scale volcanic eruptions and the fifth mass extinction caused by asteroid collisions. rice field.With this discovery, one of the first two unexplained causes has been elucidated.
Professor Kaiho and his colleagues investigated the geological formations of China and the United States, where the first mass extinction was recorded, and found a concentration of mercury.Since the concentration of mercury was also observed during the three major volcanic eruptions that occurred in another era, it is considered that this concentration was also released and deposited by the major volcanic eruption.
When a large volcanic eruption occurs, a large amount of sulfur dioxide gas enters the stratosphere and sulfates it.Sulfuric acid that covers the earth reflects sunlight, leading to global cooling.Before and after this period, the earth was in a warm period without ice sheets, but since ice sheets were found only during this period, the large-scale volcanic eruption found this time caused cooling and caused mass extinction. Was suggested.
This leaves only one mass extinction for which the cause is unknown.Further discoveries and more detailed elucidation of the extinction process are awaited.
Paper information: [Geology] A volcanic trigger for the Late Ordovician mass extinction ?: Hg data from South China and Laurentia