In a new study, researchers at the University of Colorado Boulder say they have found physical evidence for the theory that, at one time, our planet was covered in layers of ice.
Nearly 700 million years ago, a series of events completely changed the Earth’s climate. Our planet has cooled so much that it has become a gigantic “snowball”.
The scientists who supported this hypothesis, known as “Snowball Earth”, suggested that Kilometer-thick ice sheets covered the Earth’s surface and lasted for tens of millions of years. .
The curious thing is that primitive life was even able to thrive despite these conditions: when the ice caps melted on the planet, complex multicellular life appeared.
The scientific community had not obtained the evidence necessary to prove this theory, but that has now changed.
In a new study, a team of geologists claims to have found what may be proof of the “Snowball Earth” theory: a type of rocks called Tavakaiv or Tava sandstone.
Their findings were published November 11 in the journal Proceedings of the National Academy of Sciences .
“This study presents the first physical evidence that Snowball Earth reached the core of the continents at the equator,” he said in a statement. Liam Courtney Davies lead author of the study and a postdoctoral researcher in the Department of Geological Sciences at the University of Colorado Boulder.
How the Snowball Earth Theory Was Born
The concept of “Snowball Earth” was first discussed in the 1990s, when it appeared in an article by geologist Joseph Kirschvink, says a statement from the University of Colorado Boulder .
The hypothesis arose, to a large extent, from indications of sedimentary rocks that would once have been exposed on coasts and seas in addition to climate models.
Despite this, many researchers have failed to agree on whether the Earth actually froze completely. This is because while some geologists have found evidence in coastal areas, it has not been found on continents near the equator.
This is where Colorado, a state in the United States, begins to play a key role. In the past, the region was not part of North America, but was part of another supercontinent called. Laurentie which was located in northern latitudes and did not have access to the sea.
Researchers suspected that the geology of this location could provide clues to the Earth’s freezing period.
How the study was carried out
The team led by Courtney-Davies decided to focus on Tava sandstone . These sedimentary rocks, formed by injections of solidified sand, are found in the Front Range of Colorado, notably on the top of a mountain known as Pikes Peak .
In fact, the rock’s name is due to this location: Pikes Peak was called Tavá Kaa-vi by the Ute people.
Tava Sandstones may be, to most people, a common yellow to brown rock, but to scientists they are much more than that: they are believed to have originally been the surface sands of the Colorado River, and that over time they were buried underground as if they were claws digging into the earth’s crust.
“These are classic geological features called injectites that often form under some ice sheets, including in modern Antarctica,” Courtney-Davies said.
To find out if the Tava sandstones actually had a connection to the ice sheets, the University of Colorado team decided to calculate the age of the mineral veins that ran through these formations.
After collecting mineral samples, the researchers used a dating technique called laser ablation mass spectrometry. This allows minerals to be hit with a laser to release the atoms they contain.
After these tests, they discovered that the Pikes Peak formations were sunk underground, probably due to the weight of the glaciers. The phenomenon occurred during the cryogenic period, which extends between 720 and 635 million years ago.
“The origin of the Tava rocks has been debated for more than 125 years, but new technology has allowed us for the first time to conclusively link them to the Snowball Earth period.” underline the authors in an article published in The conversation .
How important is the study of Snowball Earth?
The researchers assure that these results allow us to further strengthen the “Snowball Earth” hypothesis, which has been a source of scientific debate for years.
At the same time, they assure that the fact that there are Tava injectites inside rocks covered with thick layers of threads “provides clues to other geological phenomena”.
The team assured that there were still aspects that needed to be studied, suggesting that the formations would also be found in other regions of North America besides Colorado.
Source: Latercera
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