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Scientists at the University of California, Berkeley, and Boise State University have found evidence suggesting that the Marinoan glaciation began approximately 639 million years ago and lasted for approximately 4 million years. In their study in the Proceedings of the National Academy of Sciences, the group used drone and field imagery along with isotopic dating of glacial deposits to learn more about global glaciation events during the Neoproterozoic Era.

Prior research has shown that during the early days of the planet, during the Neoproterozoic Era, Earth underwent two ice ages. The first, known as the Sturtian glaciation, lasted approximately 56 million years and covered the entire planet with ice. Less is known about the second event, called the Marinoan glaciation. In this new effort, the research team set themselves the task of figuring out when it began and how long it lasted.

The work involved sending drones over a part of Namibia, where prior research has uncovered evidence of glacial activity during the Marinoan. This allowed the team to map sedimentary layers that were stacked up in a way that showed little vertical shift had occurred, which meant the glaciers did not move much during the time they were there. Additional field imagery helped confirm what the team found in the drone images.

The team next conducted isotopic dating of ash layers that had accumulated during the time prior to the onset of the Marinoan and then as it continued. The ash layers are evidence of the volcanic activity that likely set off the ice age. They also noted patterns in the accumulated ash that suggested a single, long cold spell, rather than a series of warm and cold periods.

Taken together, the evidence allowed the researchers to pinpoint the time when the Marinoan glaciation began—approximately 639 million years ago—and how long it lasted—approximately 4 million years.

Study of both glacial events during the Neoproterozoic Era has led to questions regarding how life could have survived such cold conditions, when thick layers of ice covered the entire planet. Some have suggested it was likely due to warm geothermal vents on the ocean floor that could have served as a refuge.