‘Snowball Earth’ might have triggered giant change in carbon cycle

May 2nd, 2010 - 11:15 am ICT by ANI  

Washington, May 2 (ANI): An episode called “snowball Earth,” which may have covered the continents and oceans in a thick sheet of ice, produced a dramatic change in the carbon cycle, which in turn might have triggered future ice ages, according to a Princeton University-led team of geologists.

The research was aimed to get an insight into what can happen when the Earth’s carbon cycle is altered — a cause and consequence of climate change.

Pinpointing the causes and effects of the extreme shift in the way carbon moved through the oceans, the biosphere and the atmosphere is important for understanding just how much Earth’s climate can change and how the planet responds to such disturbances.

The researchers also presented a hypothesis to explain how changes to Earth’s surface brought by the glaciers of the Neoproterozoic Era could have created the anomaly in carbon cycling.

“The Neoproterozoic Era was the time in Earth history when the amount of oxygen rose to levels that allowed for the evolution of animals, so understanding changes to the carbon cycle and the dynamics of the Earth surface at the time is an important pursuit,” said graduate student Nicholas Swanson-Hysell, the first author on the paper.The Neoproterozoic era, which lasted from 1,000 million years ago to 542 million years ago, is divided into three distinct periods, beginning with the Tonian, extending through the Cryogenian and ending with the Ediacaran.

The Cryogenian period is notable in Earth history for the extensive and repeated ice ages that took place, beginning with the massive Sturtian glaciation at the start of the period.

This marked the first ice age on Earth in roughly 1.5 billion years, which is an unusually long time span between glaciations.

Since the Cryogenian, Earth has endured an ice age about once every 100 to 200 million years.

The “snowball Earth” theory suggests that the Sturtian glaciation was global in scope, literally encasing the planet in ice, which could have wreaked havoc on the normal functioning of the carbon cycle.

While the theory is controversial and the extent of the deep freeze is under investigation, research team member Adam Maloof showed that glaciers reached the equator some 716.5 million years ago, providing further evidence to support the existence of a Cryogenian “snowball Earth.”

In the latest research, the researchers collected samples of limestone from Central and South Australia dating back to the Tonian and Cryogenian periods.

Using a technique known as isotope analysis to learn how the carbon cycle worked in ancient times, the team pieced together clues that are hidden in the atomic composition of the carbon found in inorganic limestone sediment and ancient organic material.

In addition, the geologists recorded where the samples were found in the rock layers to determine crucial information about the relative age of the samples and the environmental conditions under which they formed.Their results documented a peculiar and large shift in the carbon cycle based on analyses of samples obtained from tropical limestone sediments known as the Trezona Formation, which dates to the end of the Cryogenian period approximately 650 million years ago and was deposited between “snowball Earth” events.

“The disturbance we’re seeing in the Neoproterozoic carbon cycle is larger by several orders of magnitude than anything we could cause today, even if we were to burn all the fossil fuels on the planet at once,” said Adam Maloof.

The team also documented that the carbon cycle was not operating in this bizarre fashion 800 million years ago prior to the first Neoproterozoic glaciations, constraining in time the onset of such behaviour and linking it to the proposed “snowball Earth” event.

The researchers have published their findings in the latest issue of the journal Science. (ANI)

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