Long before the dinosaurs there existed many other types of animals including buffalo sized reptiles. Many died out in a mass extinction during the Capitanian Age roughly 260 million years ago. A new study suggests that this mass extinction was actually not one event but two, separated by nearly 3 millions years. Both were caused by massive volcanic eruptions.
By studying uranium isotope profiles of marine samples collected in the South China Sea, scientists discovered two “pulses” in which the oceans became deprived of oxygen.
By studying these ancient extinctions, researchers can better predict how present global warming could affect the ocean’s food chain.
“We are studying the biocrisis in the Permian Period, but similar warming is happening today because of human events,” said Thomas Algeo, study co-author. “Humans are mimicking the effects of volcanic eruptions as a consequence of the release of carbon into the atmosphere.”
Algeo explained that massive eruptions create a brief period of cooling from ash in the upper atmosphere reflecting sunlight, followed by much longer periods of global warming. The explosion of massive volumes of greenhouse gases warmed the oceans. Also, the warm surface water did not allow dissolved oxygen to reach lower depths, eventually destroying the food chain.
“The ocean is teetering on the edge of anoxia,” he said. “Dissolved oxygen has to be taken up by the surface layer and supplied to the deep ocean. But warmer water is lower density. When you increase the density differential, you prevent any overturn and there’s no way to get dissolved oxygen into the deeper layers.”
https://phys.org/news/2023-04-geology-experts-evidence-dual-mass.html