American geophysicists named the reason why the Earth was almost completely covered with snow several hundred million years ago. The corresponding study is published in the journal Geophysical Research Letters, briefly reported by Harvard University.
According to scientists, the reason that 717 million years ago for about one hundred thousand years, most of the icing, was volcanic activity in place of the Franklin magmatic province, located in the territories of modern Alaska and Canada.
Eruptions led to ejection into the tropopause (a layer of the gas shell between the troposphere and stratosphere, located at an altitude of 6-20 kilometers), sulfur dioxide and hydrogen sulfide. These compounds led to the formation in the stratosphere of sulfate aerosols – droplets that reflect sunlight and thus reduce the heating of the underlying layers of the atmosphere and the surface of the planet. During volcanic activity, this, according to the authors, led to a decrease in the height of the tropopause.
Scientists note that the eruption of the Pinatubo Volcano on the Philippine island of Luzon in 1991 led to the release of ten million tons of sulfur into the atmosphere, which during the year reduced the global temperature by about 0.5 degrees Celsius. The authors also note the presence of a feedback loop – the increase in volcanic activity in antiquity, when the glaciation spread to the territory of modern California, led to an even more intense reflection of the ice by the sunlight and the subsequent even faster cooling of the planet.
Previously, scientists knew that the formation of the Franklin magmatic province and the first global glaciation of the Neoproterozoic era occurred about the same time. The study revealed a possible causal relationship between the phenomena.