Researchers have found evidence that the Earth was not completely solid during the Marian Ice Age, 635 million years ago. Shallow mid-latitude seas remained ice-free, which could help sustain life. Credit: Michael Miller
At least five ice ages have occurred on Earth, including one 635 million years ago that created glaciers from pole to pole.
It’s called the Pleistocene Marinwan, named after the part of Australia where geological evidence was first collected in the 1970s.
Scientists say the Marinwan Ice Age was one of the most extreme in the planet’s history, creating glacial ice that lasted for 15 million years.
But new evidence collected in the eastern forested region of Shennongjia, China’s Hubei Province, suggests that the Earth was not completely frozen over — at least not at the end of the Ice Age. Instead, there were patches of open water in some shallow, mid-latitude seas, based on geological samples dating back to the period.
“We have called this ice age Snowball Earth,” said Thomas Algeo, professor of earth sciences in the University of Cincinnati’s College of Arts and Sciences. “We thought the Earth had completely frozen over during this long ice age. But it may have been more of a “hard ball ground.”
The study has been published in the magazine Nature Communications.
Scientists found benthic, photosynthetic macroalgae in black shale dating back more than 600 million years. These algae live on the sea floor and need sunlight to convert water and carbon dioxide into energy through photosynthesis.
University of Cincinnati geology professor Thomas Algeo and colleagues have discovered isotopic evidence that some mid-latitude seas remained ice-free during the Marinoan Ice Age known as the Earth’s Snowball. Credit: Andrew Higley
A team of geoscientists from China, the United Kingdom and the United States conducted an isotope analysis and found that the habitable conditions of the open ocean were more extensive than previously thought, extending into the oceans that lie between the tropics and the polar regions and provide a refuge for a single person. Multicellular and multicellular organisms during the waning phases of the Marinoan Pleistocene.
While it is likely that deep waters did not have oxygen to support life during this period, said lead author Huyue Song of the China University of Geosciences, shallow seas did.
“We present a new Snowball Earth model in which open water is found in the oceans of low and middle latitudes,” Song said.
The Ice Age likely saw several periods of freezing and thawing over the course of 15 million years, Song said. Under such circumstances, Song said, life could have gone on.
University of Cincinnati geology professor Thomas Algeo examines rock cores in his lab. He and his colleagues discovered isotopic evidence that some mid-latitude seas remained ice-free during the Marinoan ice age known as Snowball Earth. Credit: Andrew Higley
“We found that Marinuan glaciation was dynamic. There may have been potential open water conditions in low and middle latitudes several times,” Song said. “In addition, these surface water conditions may be more widespread and sustainable than previously thought, and may have allowed a rapid recovery of the biosphere after the planet’s Marinova.”
Ironically, said Algeo of the University of California, these refuges of life likely helped warm the planet, ending the Ice Age at Marinoan. Algae in the water released carbon dioxide into the atmosphere over time, gradually melting the glaciers.
“One of the general take-home messages is how much the biosphere affects the carbon cycle and climate,” he said. “We know that carbon dioxide is one of the most important greenhouse gases. So we see how changes in the carbon cycle affect the global climate.”
Algeo said the study raises tantalizing questions about other ice ages, particularly the second during the Cryogenian period that scientists also believe triggered an almost complete glaciation of the planet.
University of Cincinnati geology professor Thomas Algeo and colleagues have discovered isotopic evidence that some mid-latitude seas remained ice-free during the Marinoan Ice Age known as the Earth’s Snowball. Credit: Andrew Higley
“We don’t know for sure what caused these ice ages, but my suspicion is that they were related to multicellular organisms that removed carbon from the atmosphere, burying the carbon and cooling the Earth,” Algeo said. “Today, we are releasing carbon rapidly and in huge quantities and it has a huge impact on the global climate.”
more information:
Huyue Song et al, A mid-latitude habitable environment for marine eukaryotes during the waning phase of the Marinwan snowball glaciation, Nature Communications (2023). DOI: 10.1038/s41467-023-37172-x
the quote: Snowball Earth may be a slushball (2023, April 9) Retrieved April 9, 2023 from https://phys.org/news/2023-04-snowball-earth-slushball.html
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