Evidence from Colorado shows that glaciers once covered the Earth up to the equator, supporting the snowball Earth theory. This discovery sheds light on early climate change and the evolution of life. Geologists have found compelling evidence in Colorado that hundreds of millions of years ago, massive glaciers covered the Earth up to the equator, turning the planet into an icicle drifting through space.
The study, conducted by the University of Colorado at Boulder, is a blow to supporters of the old theory known as snowball Earth. It suggests that between about 720 and 635 million years ago, for reasons that are still unclear, a continuous chain of events radically changed the planet’s climate. Temperatures dropped and ice sheets that could be several miles thick covered every inch of the Earth’s surface.
“This study provides the first physical evidence that Snowball Earth has reached the heart of the continents at the equator,” said Liam Courtney-Davis, lead author of the new study and a postdoctoral researcher in the CU Boulder Department of Geological Sciences.
The team published their findings Nov. 11 in the journal. Proceedings of the National Academy of Sciences . Co-authors include Rebecca Flowers, professor of geological sciences at the University of Boulder, as well as researchers from Colorado College, University of California, Santa Barbara, and University of California, Berkeley.
The study focuses on the Front Range of the Colorado Rockies. A series of rocks called the Tawakai sandstones, or “Tawa,” hold clues to this cold period in Earth’s past, according to Courtney-Davis.
The researchers used a dating technique called laser ablation mass spectrometry, which etches minerals with lasers to release some of the atoms inside. They showed that these rocks were thrown underground about 690-660 million years ago, most likely due to the weight of huge glaciers pressing down on them.
Courtney-Davis added that the study will help scientists understand a critical phase not only in the geological history of the planet, but also in the history of life on Earth. The first multicellular organisms may have appeared in the oceans soon after the snow-covered Earth melted.
“Your climate evolves, and life evolves with it. All of this happened during the upheaval on Snowball Earth,” he said. “We need to better characterize this entire time period to understand how we and the planet evolved together.”
looking for snow
The term “Snowball Earth” is based on a 1992 paper by American geologist Joseph Kirschwink. But despite decades of research, scientists still disagree on whether the entire Earth is truly frozen. For example, geologists have found traces of thick ice from this period in ancient coastal areas, but not within continents near the equator.
This is where Colorado comes into play. At that time, the region was not located at today’s northern latitudes. Instead, Colorado was located above the equator as part of the ancient landlocked supercontinent Laurentia. Scientists believe that if glaciers formed here, they could have formed anywhere.
Respiration
Their search for the missing piece of the puzzle led Courtney-Davies and her colleagues to the Tawa Sandstones. Today, these features emerge from the ground in several locations along Colorado’s Front Range, particularly in the Pikes Peak region. To the untrained eye, these may appear to be ordinary yellow-brown rocks ranging from less than an inch wide to many feet wide in vertical stripes.
But for geologists, these features have an unusual history. They likely began as sand on the surface of Colorado at some point in the past. But then forces pushed them underground, as if claws had dug into the earth’s crust.
“These are classic geological features called injections that often form beneath some ice sheets, including present-day Antarctica,” said Courtney-Davis.
He wanted to find out whether the Tava sandstones were also related to ice sheets. To do this, the researchers calculated the age of the mineral veins that cut these elements. They collected small samples of minerals rich in iron oxide (essentially rust) and then hit them with a laser. In this process, the minerals released small amounts of the radioactive element uranium. Because uranium atoms decay into lead at a constant rate, the team can use them as a kind of timekeeper for the planet’s rocks.
It was a Eureka moment: The team’s findings showed that the Tawa Sandstone was pushed underground during the Snowball Earth. The group suspects that thick ice sheets formed over Colorado at that time and the sands were subjected to intense pressure. Finally, having nowhere else to go, they pushed against the rock.
“We are pleased to have the opportunity to uncover the history of the only Snowball Earth deposits discovered so far in Colorado,” said Flowers.
Researchers aren’t done yet: If such elements formed in Colorado during Snowball, they likely formed elsewhere in North America, said Courtney-Davis: “We want to spread the word so others can try to find them and make Snowball Earth more complete.” Help us create a picture of it.”
Source: Port Altele
