Over its relatively young 4.54 billion years of existence, Earth has been host to a number of awe-inducing geological phenomena and climate changes, including the time it turned into a massive snowball. A new study claims that the “snowball Earth” phase occurred 717 million years ago.
What led “snowball Earth” or pole-to-pole glaciation on the green planet to take place?
‘Snowball Earth’ Explained
Earth’s freezing, or a period when it was covered almost entirely in ice from the poles to the tropics, is believed to have happened in the pre-Cambrian era. Episodes of “snowball Earth” are claimed to have taken place before the abrupt radiation of multicellular life forms dubbed the “Cambrian explosion.”
Supporters of this hypothesis believe that the event occurs once in a billion years, the last one said to be key in how so-called “multicellularity” evolved.
Scientists initially believed that a chemical reaction between carbon dioxide in the air and basaltic rock could have made ice form. However, that could take a considerable amount of time, so researchers instead eyed the dumping of huge amounts of aerosol into the atmosphere due to continuing volcanic eruptions that rapidly cooled the planet.
Continual Volcanic Eruptions
A new study suggested that it’s no coincidence that around the time that Earth turned into a giant snowball, present-day Alaska to Greenland was undergoing catastrophic volcanic eruptions.
Harvard University scientists investigated how the eruptions in the area were actually different.
“These types of eruptions have happened over and over again throughout geological time but they’re not always associated with cooling events,” said study author Robin Wordsworth in a Daily Mail report.
The team noted that in the region called the Franklin large igneous province, volcanic rocks erupted via sulfur-laden sediments. This would have been shot into the atmosphere as sulfur dioxide, something blocking the sun’s rays and cooling off the temperature to a number of degrees.
When it gets past the tropopause where it is less likely to return to Earth by precipitation, it can stay in the atmosphere for a year.
Throughout Earth’s geological history when it was extremely warm, volcanic cooling would not have made a drastic difference since the planet is protected by the high and warm tropopause, Wordsworth explained. But cooler conditions are a different matter: Earth becomes quite sensitive to volcano-induced unease in climate.
Imagine continual eruptions in a period spanning 2,000 miles, with enough aerosols in the atmosphere to shake the current climate. The cooling from aerosols can drive the ice to a critical point, said associate professor Francis Macdonald.
As ice built up, the surface reflected back sunlight and caused Earth to cool further. Once the ice hit a certain latitude, a runaway snowball effect ensued, according to the team.
A recent study concluded that massive volcanoes spat out lava over ancient Earth much frequently than thought, with such eruptions associated with profound planetary changes that include the largest mass extinction that occurred 252 million years ago.
As for studying the snowball effect that struck Earth millions of years earlier, researchers hoped these studies can help humans better understand past extinctions and plan ways to potentially deal with future changes in climate.