About 650 million years ago, during a vast 15 million year period, the Earth was plunged into a terrible ice age. Recent studies suggest that as this period drew to a close, the Earth may not have completely frozen over.
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The exploration concluded that the planet was more likely to have resembled a “slushy ball” than a “snowball,” with evidence of water in shallow seas at midlatitudes. This seemingly inhospitable condition may have been instrumental in sustaining life during this extreme period on Earth.
Scientists recently discovered evidence of the past by examining samples from the Shennongjia Forest Area of Hubei Province in China , an area believed to be associated with the last days of the Marinoan glaciation 628-623 million years ago .
The Marino period was one of the most extreme ice ages in Earth's history, so much so that it was nicknamed "Snowball Earth." "We thought the Earth was completely frozen during this long ice age," University of Cincinnati geosciences professor Thomas Algeoin a statement. "But it may have been more of a mud Earth."
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Algeo and his team discovered striking evidence of a saltwater flora known as benthic phototrophic macroalgae. This form of algae is embedded in black shale, a dark sediment composed of organic material that has been deposited over many centuries on Earth. This distinctive black shale dates back to the Marinoan glaciation, which occurred about 600 million years ago.
Algae species that live in the depths of our oceans need sunlight for photosynthesis – an essential process in which sunlight is used to convert water and carbon dioxide into energy. Huyue Song, lead researcher from the China University of Geosciences, argued that while oxygen was absent in the deep waters during this period, the shallow seas contained it.
This suggests that habitable conditions in the oceans may have been wider than initially assumed, and could have even reached seas between the tropics and the poles. Life forms, such as single-celled and multicellular organisms, could have settled in these open oceans when the Martian ice age came to an end, allowing our planet to thaw.
Algae in the water released carbon dioxide, a greenhouse gas that trapped heat and eventually led to the melting of glaciers.
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It is not certain what triggered these ice ages, however it is believed that it may be linked to multicellular organisms that extracted carbon dioxide from the atmosphere, which led to its elimination and consequently to the cooling of our planet.
The team's research is published in the journal Nature Communications.
