The three great geological eras dominated by dinosaurs were the Triassic, the Jurassic and the Cretaceous. They were not identical at all. These include hundreds of millions of years apart, unique climatic conditions, different dominant organisms, and different extinctions. A recent study by the Columbia Climate School proposes an alternative ending for the first dinosaurs that populated the planet, when the supercontinent Pangea existed.
Not all dinosaurs became extinct for the same reason or at the same time. To determine the causes of its disappearance, paleontology debates between several hypotheses, according to the available evidence. For example, the dinosaurs of the Cretaceous period, the period of greatest proliferation of species, probably became extinct due to the impact of an asteroid 10 kilometers in diameter and its environmental consequences. Meanwhile, the Triassic dinosaurs, by scientific consensus, became extinct due to the consequences of the geological activity in their environment.
The new Columbia study proposes that it was specifically the cold that wiped out the Triassic dinosaurs, making way for all the Jurassic species. Until recently, scientists estimated that anomalous warming of the planet, due to volcanic activity caused by the natural separation of Pangea, was responsible. This theory suggests that carbon dioxide ejected from the planet’s surface had formed a kind of greenhouse effect unsustainable for life and acidified the oceans, wiping out most species.
The volcanic winter of the Triassic
Scientists at the Climate School’s Lamont-Doherty Earth Observatory have found evidence to the contrary. Instead of being events that happened over hundreds of thousands of years, the lava ejections would have been abrupt and abundant. A large proportion of sulfates expelled by these volcanoes would have reached beyond the planet’s atmosphere, and their reflective properties would have prevented the passage of light rays, concludes the study published in Proceedings of the National Academy of Sciences.
Geology refers to these cold events after constant eruptions such as volcanic winters. They work as follows: an erupting volcano releases sulfur dioxide. The sulfurous gas combines with water vapor to form sulfuric acid and is eventually transformed into sulfate aerosols. These particles reflect and scatter solar radiation, limiting the light that naturally reaches the planet. In the last 200 years, the planet has faced two similar specific events: the eruption of Mount Tambora, Indonesia, in 1815, and that of Mount Pinatubo, Philippines, in 1991.
The research took data from the Central Atlantic Magmatic Province (CAMP), one of the largest igneous zones on the planet. Its formation, 200 million years ago, is linked to the breakup of Pangea and the opening of the Atlantic Ocean. In CAMP deposits in Morocco, Scotland and New Jersey, scientists found magnetic particles that revealed the frequency of lava pulses in the late Triassic period.
A variety of volcanoes on the great continent erupted in a period of less than 100 years. The release of sulfates by the volcanic pulse was so great that the Sun was “almost blocked” and the drop in temperatures was irremediable. Aerosols, by nature, do not last long, so it is estimated that that volcanic winter did not last that long. However, scientists estimate that up to 50% of marine species and 25% of terrestrial species disappeared after the Triassic climate event.
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