Frequent and severe eruptions led to Triassic extinction, when half the species disappeared from the face of the Earth. The liberated ecological niches were cleverly occupied by giant lizards, and during the Jurassic period they experienced a real flowering.
This conclusion was made by scientists at Oxford University (Great Britain), measuring the level of mercury in igneous rocks of the end of the Triassic – the beginning of the Jurassic period. It turned out that the rise in the concentration of mercury, which indicates a jump in volcanic activity, was correlated with Triassic extinction.
Our planet has experienced five major mass extinctions. The largest was the Permian extinction (250 million years ago), which removed 90% of the fauna from the face of the earth. The most recent Cretaceous-Paleogene extinction (66 million years ago) permanently deprived us of dinosaurs.
Triassic extinction occurred at the junction of the Triassic and Jurassic periods. The extinct ancestors of mammals and arhosaurs gave way to dinosaurs, which, having no competitors, began to develop by leaps and bounds.
The causes of Triassic extinction are a matter for disputes among scientists. Then the climate change has uniquely happened, but it is not known what it was caused by – an asteroid impact, instability of the world ocean level or volcanic eruptions.
Supporters of the volcanic version argue their position by the fact that the Triassic extinction occurred at one time with the formation of huge basaltic deposits – the Central Atlantic magmatic province. The layers of basalt in the sediments alternate with the layers of rock containing organic carbon.
This means that volcanoes periodically erupted on Earth, which threw out not only lava, but also clouds of gas. Gas emissions contained mercury, which has survived to our days in sedimentary rocks. The maximum value of mercury fell into the strata of the rock at the boundary of the Triassic and Jurassic period, when extinction was in full swing.
Scientists believe that the animals of the Triassic period destroyed not directly the mercury itself, but the increase in CO2 in the atmosphere due to volcanic activity. The increased concentration of carbon dioxide led to climate change, which the animals could not endure.