Frozen Earth: Global glaciation event lasted 4 million years

Some ancient periods in Earth’s history challenge our assumptions about what our planet can endure. The earliest global glaciation event of the Neoproterozoic Era, known as the Sturtian glaciation, lasted 56 million years and turned the planet into a “snowball” all the way to the equator.

A second snowball glaciation, the Marinoan glaciation has been more difficult to pin down in terms of duration and extent.

Evidence of global glaciation

In 2025, a research team led by Adrian R. Tasistro-Hart from the Department of Earth and Planetary Science, McCone Hall, at the University of California, presented findings that link the structure of certain rock layers to this second massive chill in the Neoproterozoic Era.

The study provided direct dating evidence of this widespread freeze, and helped tackle a puzzle that has long intrigued geologists.

Clues from rock formations in Namibia, southwestern Africa, suggested that long-lasting sheets of ice reached these areas that were previously thought to have been spared. This enabled the researchers to date the onset and duration of the Marinoan glaciation event.

The field data suggested an unexpected stability in the frozen surface that lasted around 4 million years. This raises questions about how life managed to persist during these extreme times.

Clues about a frozen Earth

Scientists have spent decades studying ancient sediments to understand the causes behind major planetary cool-downs. Some layers reflect glacial activity in places as distant as southwestern Africa, with rugged terrain that extends for about 11 miles (18 kilometers) in certain study zones.

Evidence from drone imagery and core samples in this area hints at ice piles that never budged even when orbital changes caused the usual shifts in climate. This pattern suggests a stability in conditions that leaves researchers wondering why none of the typical fluctuations were recorded.

Such steadiness separates this period from shorter glacial intervals that were seen in more recent times. It also indicates that small differences in volcanic activity might lead to dramatic changes in how our planet traps or reflects heat.

What caused the global glaciation event?

Earth radiates much of the Sun’s energy back out into space under normal circumstances. Sometimes, volcanic activity can produce clouds of gas and dust that increase albedo (the proportion of solar radiation that is reflected) and block incoming solar radiation.

This would have cooled the Earth and potentially triggered a run-away glaciation event. As more ice formed and began to cover not just polar regions, the incoming solar radiation was likely insufficient to counteract the reflective nature of this white covering, which led to the Earth’s becoming locked in a long cycle of freezing temperatures.

A tipping point in the atmosphere

Volcanoes kept pumping CO₂ into the atmosphere, but the thick ice would have hampered normal silicate weathering. This is a chemical reaction in which rainwater – slightly acidic from the presence of dissolved carbon dioxide – interacts with silicate minerals in rocks and helps remove CO₂ from the atmosphere to be stored in the ocean.

By slowing this process, the removal of CO₂ was reduced and the levels of this greenhouse gas gradually increased. A buildup of CO₂ in the air eventually led to global warming which caused surface temperatures to rise, though it took a huge concentration to break free from the extended freeze.

Researchers suspect that minor factors, like the dustiness of the ice sheets, could have accelerated the meltdown by decreasing reflectivity. 

This shift challenges typical models that focus on gradual geological changes over shorter spans. The planet may have lingered in an icy standstill until the atmosphere reached a tipping point, which set off a dramatic thaw.

Patterns found in rock and volcanic ash

The researchers chose to study an area in Namibia where sediments provide a rare record of snowball onset during the Marinoan glaciation. Drone mapping revealed sedimentary layers stacked in ways that show minimal vertical shifts.

The contact points between distinct rock beds appear consistent, implying that grounded ice stayed in place during the Marinoan glaciation for ages.

No large scouring marks or abrupt breaks were identified, and that silence in the record indicates subdued glacial motion. Researchers interpreted one zone of minimal erosion to mean the grounding line never bounced around, which is rare in studies of prolonged ice coverage.

Patterns in buried volcanic ash lend further clues. A single layer might become entombed, signifying calm accumulation rather than the usual push and pull of warmer spells.

Isotopic dating of the ash layers in various locations indicated that the Marinoan glaciation onset began 639 million years ago and lasted around 4 million years.

How did life survive global glaciation?

A global freeze of that scale raises questions about how organisms survived beneath thick ice. Anaerobic communities could have lived off chemical nutrients, but others may have endured near cracks or in sheltered marine pockets.

Researchers debate whether oxygen levels dropped enough to challenge more complex life forms. The resilience of certain species appears remarkable, given the extreme conditions that blocked sunlight and isolated habitats.

An abrupt rebound in temperatures could have triggered bursts of evolution, setting the stage for Ediacaran ecosystems to emerge. Scientists continue to explore how these expansions followed such a prolonged ice event.

A refuge beneath the ice

Some scientists believe that pockets of liquid water beneath the ice provided refuge for early life. These subglacial ecosystems could have been sustained by geothermal heat, allowing microbial life to persist even in the absence of sunlight.

Chemical nutrients released by hydrothermal vents or rock-water interactions may have fed these organisms, setting the stage for survival during global freezes. Once the ice retreated, these life forms could have re-emerged and diversified rapidly.

Looking to other worlds

Researchers mention that findings like these expand discussions about habitability on exoplanets that are locked in ice. If a planet undergoes a global glaciation, the accumulation of greenhouse gases might eventually spark an intense thaw.

That thaw could reshape its atmosphere and allow liquid water, paving the way for more complex chemistry. Another planet might remain stuck in an icy state if certain tipping points are never reached.

“The disparity in durations [between the Sturtian and Marinoan glaciations] demonstrates different routes to deglaciation,” said Tasistro-Hart.

The researchers noted that every icy scenario can have its own exit strategy. This study offers a fresh perspective on the dynamic relationship between geology and climate. 

The study is published in the journal Proceedings of the National Academy of Science.

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