The second surge of the Ordovician-Silurian extinction occurred due to global warming: volcanic activity has led to increased ocean temperatures, its acidification and anoxia — reducing the concentration of dissolved oxygen. To such conclusions scientists have come, having studied the sediments in the stratotype section Dobs Linn. According to their study, the results of which are published in the journal Geology, there is now reason to believe that all five mass extinctions in Earth’s history have been associated with global warming.
In the history of our planet there have been five mass extinctions — the Ordovician-Silurian (450-443 million years ago), Devonian (372 million years ago), Permian (253-251 million years ago), Triassic (208-200 million years ago) and the Cretaceous-Paleogene (65.5 million years ago). In fact, the real causes of these events are set almost impossible, but you can build a hypothesis based on data extracted from ancient deposits of rocks.
At the moment theory of the origin of four of the five mass extinctions, all but the Ordovician-Silurian — based on global warming. Volcanic activity (including underwater) led to emissions of greenhouse gases and the warming of the planet, the waters of the seas was sakalelis, and oxygen dissolved in them worse and it became disastrous for many species of living organisms.
Ordovician-Silurian extinction had two bursts with an interval of one million years and resulted in the deaths of 85 percent of species. For its first phase, no evidence of warming in that era were found. On the contrary, it was associated with the influence of Gondwana glaciation, and therefore it’s distracting from the overall picture of mass extinctions, because all the others were found relationships with volcanic activity.
Scientists under the direction of David bond (David P. G. Bond) from the University of hull studied the sediments in Dobs Linn (South of Scotland), where in the summer of 2018 due to the dry conditions revealed a previously submerged parts of the banks of the Creek Lynn Branch. They took 62 of the sample in outcrops of the stream of layers with a thickness of two inches across and 25.5 meters of the upper shale and slate Hartville Birkhill and 10 samples in the stratotype Dobs Linn, to fill poorly represented in the main section of the upper shale.