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Stephen Chen

Acid rain might have deluged the entire globe for hundreds of thousands of years after the melting of “snowball Earth” more than 600 million years ago, according to a new geological discovery in China.
But the “hellish” event might also have spurred the emergence of complex life forms in the “Cambrian explosion”, researchers said.
The discovery of ancient relics of massive glaciers in similar geological stratums around the world led scientists to suspect that ice has covered our planet almost entirely at least twice. Each episode lasted for millions of years, with ice sheets up to 2km thick extending from the poles to the equator.
Sea ice in Arctic and Antarctic at record lows as scientists point to global warming ‘triple whammy’
The most recent “snowball” episode, known as the Marinoan glaciation, gripped the planet from 650 million years ago to 635 million years ago. The ice and snow reflected sunlight like a mirror, causing temperatures to plunge dramatically.
But that led to a question: what caused the snowball to melt?

One popular theory was that an enormous amount of greenhouse gases, mostly carbon dioxide, built up in the atmosphere due to volcanic activity. The greenhouse effect eventually overcame the icy reflections, leading to a rapid temperature increase and the melting of nearly all the ice in as little as 2,000 years.
All that was missing was evidence.
China’s smog clouds have a silver lining: they may help prevent global warming, claims new study
Today’s global warming is generally blamed on human activity, but carbon dioxide levels in the atmosphere at the end of the Marinoan episode were more than 500 times greater than present levels. That would have led to acid rain and the erosion of exposed landscapes due to chemical reactions called weathering. However, no evidence of chemical weathering in the Marinoan period had been found.
An international research team led by Professor Shen Bing, from Peking University’s school of earth and space sciences, said they might have found the long-sought evidence in a rocky layer above a Marinoan glacial deposit in Hunan province’s Nantou formation.

Analysis of magnesium isotopes from the site, which acted as chemical “fingerprints”, revealed intense chemical weathering during the melting of Marinoan glaciers.
The erosion was “extremely strong”, the researchers said in a paper published in the journal Proceedings of the National Academy of Sciences in the United States on Tuesday.
The melting increased vapour in the air, which helped the formation of acid storms. Huge floods devastated every ancient continent, sweeping huge amounts of debris into highly acidic oceans, where most of it dissolved. Only a few sites were buried, among them the deposits discovered in China.
Quakes vs global warming: Seismic activity found to reduce greenhouse gases, combat acidification in oceans
The researchers said the acid rain might have continued for hundreds of thousands of years.
“Fortunately nothing lived out there ... no plants, certainly no animals, just some micro-organisms in the ocean,” Shen told the South China Morning Post.
“But it was warm,” he added – the only similarity to the world today.

The global warming following the snowball episode was believed to have paved the way for the Cambrian explosion, a short evolutionary event about 541 million years ago in which complex animal life forms appeared on Earth for the first time.
The Peking University study found new evidence for that hypothesis, too.
The researchers found that chemical weathering on the ancient continents might have consumed up to 99 per cent of the carbon dioxide in the atmosphere, with the debris washed into the oceans reducing their acidity too.
Atlantic Ocean soaks up heat to slow global warming, scientists believe
The reduction in carbon dioxide enabled the formation of a special layer of rock called cap carbonate on ocean floors, which was also discovered by the researchers at a site in the Duoshantuo formation in neighbouring Guizhou province.
The cap carbonate was formed by “dust” falling from the surface of the oceans, and the researchers said the same process might also have carried the nutrition crucial for the development of larger and more sophisticated animal life forms in the oceans.


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Science

What caused ‘snowball Earth’ to melt? Researchers find evidence in China

Acid rain that deluged planet linked to emergence of complex life forms

Lit by moonlight in a long exposure photograph, Portage Glacier and the snowy peaks of Chugach National Forest glow at night, March 19, 2013, about 50 miles south of Anchorage, Alaska. Portage Lake is a popular cross-country ski destination in late winter and early spring. (Marc Lester/Anchorage Daily News/MCT)

epa04203177 A handout picture made available by NASA on 13 May 2014 shows a multi-layered lenticular cloud hovering near Mount Discovery, a volcano about 70 km southwest of McMurdo Station on Ross Island, Antarctica, 24 November 2013. In 43 hours across five science flights in late November 2013, NASA's P-3 research aircraft collected more than 20,000 km worth of science data. Instruments gathered information about the thickness of the ice over sub glacial lakes, mountains, coasts, and frozen seas. The flights over Antarctica were part of Operation IceBridge, a multi-year mission to monitor conditions in Antarctica and the Arctic until a new ice-monitoring satellite, ICESat-2, launches in 2016. Lenticular clouds are a type of wave cloud. They usually form when a layer of air near the surface encounters a topographic barrier, gets pushed upward, and flows over it as a series of atmospheric gravity waves. Lenticular clouds form at the crest of the waves, where the air is coolest and wate

The Thwaites Glacier in Antarctica is seen in this undated NASA image. Vast glaciers in West Antarctica seem to be locked in an irreversible thaw linked to global warming that may push up sea levels for centuries, scientists said on May 12, 2014. Six glaciers including the Thwaites Glacier, eaten away from below by a warming of sea waters around the frozen continent, were flowing fast into the Amundsen Sea, according to the report based partly on satellite radar measurements from 1992 to 2011. REUTERS/NASA/Handout via Reuters (ANTARCTICA - Tags: ENVIRONMENT SCIENCE TECHNOLOGY) ATTENTION EDITORS - FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

Saturn's moon Enceladus, covered in snow and ice, resembles a perfectly packed snowball in this image from Nasa's Cassini mission. Earth may have looked similar more than 600 million years ago. Photo: Nasa

What caused ‘snowball Earth’ to melt? Researchers find evidence in China

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Acid rain that deluged planet linked to emergence of complex life forms

Acid rain that deluged planet linked to emergence of complex life forms