About 720 to 635 million years ago, Earth cooled so much that scientists believe almost its entire surface was covered in a thick layer of ice, including continents and oceans. This phenomenon called “Snowball Earth” or “Ice Ball Earth” would have lasted for tens of millions of years. When the ice melted, multicellular life emerged, giving rise to the life forms we know today.
While evidence of this ice age has been found in various regions, no trace has been found in the interior of continents close to the equator – until now. A new study published in Proceedings of the National Academy of Sciences on November 11, 2024, highlighted by The Conversationreveals that a rock discovered on Pikes Peak in Colorado (United States) could fill this missing link.
According to study leader Liam Courtney-Davies, these yellow-brown-looking sandstones (sedimentary rocks), called “Tava” by indigenous peoples of America, contain clues to this glacial period in Earth’s past. These rocks would have been formed under the immense pressure of an ice sheet, pushing sand-rich sediments mixed with meltwater into the underlying rock.
To confirm their hypothesis, the researchers used a technique called “laser radiometric dating,” which involves destroying minerals using lasers to release some of the atoms they contain. Result: these rocks were formed approximately 690 to 660 million years ago, corroborating their formation under the weight of enormous glaciers bearing down on them.
A mystery slowly unraveled
The causes of this extreme cold remain debated. Among the theories: tectonic changes that released particles into the atmosphere reflecting sunlight, followed by an accumulation of CO2 volcano which would have warmed the planet. Or even because of an asteroid.
During the time of Snowball Earth, Colorado was on the equator as a landlocked part of the ancient supercontinent Laurentia, and the Tava rocks found on Pikes Peak are believed to have formed near the equator. If glaciers formed in Colorado, scientists believe they could have formed anywhere on Earth.
Liam Courtney-Davies highlights the importance of the study: “Better characterizing this period allows us to understand how we and the planet evolved together. If such features formed in Colorado during Snowball Earth, they likely formed in other places in North America as well.” Researchers hope the secrets of these elusive Colorado rocks will lead to the discovery of other traces of Snowball Earth.
Source: www.slate.fr
