American geophysicists have named the reason why several hundred million years ago the Earth was almost completely covered with snow. A related study was published in Geophysical Research Letters and is briefly reported by Harvard University.
According to scientists, the reason that 717 million years ago, over about a hundred thousand years, most of it was frozen over, was volcanic activity on the site of the Franklin magma province, located in the territories of modern Alaska and Canada.
The eruptions led to the release of sulfur dioxide and hydrogen sulfide into the tropopause (a layer of the gas envelope between the troposphere and the stratosphere, located at an altitude of 6-20 kilometers). These compounds led to the formation in the stratosphere of sulfate aerosols - drops that reflect sunlight and thus reduce the heating of the underlying layers of the atmosphere and the planet's surface. During volcanic activity, this, according to the authors, led to a decrease in the tropopause height.
Scientists note that the eruption of Mount Pinatubo on the Philippine island of Luzon in 1991 released ten million tons of sulfur into the atmosphere, reducing global temperatures by about 0.5 degrees Celsius over the course of a year. The authors also note the presence of a feedback loop - an increase in volcanic activity in antiquity, when glaciation spread up to the territory of modern California, led to an even more intense reflection of sunlight by ice and an even faster cooling of the planet.
Previously, scientists knew that the formation of the Franklin igneous province and the first global glaciation of the Neoproterozoic era took place at about the same time. The conducted research revealed a possible causal relationship between the phenomena.