According to new studies based on the analysis of shell fossils off the island of Seymour in Antarctica, the Earth was already unstable in terms of environment and climate even before the impact of the asteroid that led to mass extinctions, including that of dinosaurs occurred about 66 million years ago.
Researchers at Northwestern University, funded by the National Science Foundation, have in fact measured the isotopic composition of calcium inside the shells of various fossilized molluscs and snails dating back to the period of mass extinction of the Cretaceous-Paleocene. The chemistry of these shells seems to have changed in response to an increased presence of carbon in the oceans, even before the impact of the asteroid off the coast of Mexico.
Most likely, as researchers report, this increased influx of carbon into the oceans was caused by the eruptions of a long-term phenomenon such as the Deccan traps, a very large volcanic province covering more than 200,000 square miles, located in areas of modern India. These repeated eruptions released enormous quantities of carbon dioxide into the atmosphere, which led to the acidification of the oceans, an acidification that researchers then “measured” through chemical analysis of these fossils.
According to Andrew Jacobson, senior author of the study, these results show that the Earth was already clearly under stress before the great mass extinction event and that the impact of the asteroid does not coincide with the instability of the carbon cycle that already existed. This raises further doubts that only the impact of the asteroid could have caused the extinction.
The study was published in Geology.
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