“Snowball Earth” Caused Major Changes in Past Carbon Cycle
05.05.2010 - Atmosphere & Space, Land & Geology, Bi-polar
A new study recently published in the journal Science suggests that an episode known as “snowball earth”, which occurred some 720 million years ago, may have produced a dramatic change in the carbon cycle. This change could have in turn triggered future ice ages.
The Neoproterozoic Era is a time when levels of oxygen rose sufficiently to allow the evolution of animal life. The period, which began some 1,000 million years ago and lasted until 542 million years ago, is divided into three distinct periods: the Tonian, the Cryogenian and the Ediacaran. Ever since the Cryogenian, the Earth has been witnessing an ice age every 100 to 200 million years.
By sampling limestone from Central and South Australia dating back to the Tonian and Cryogenian periods, and applying an isotope analysis, the team gained better insight in the working of the carbon cycle at that stage in history. Moreover, by recording the location of the samples inside the rock layers, the team was able to derive crucial information to determine the relative age of the samples and the environmental conditions under which they were formed.
Their results show a major disturbance in the Neoproterozoic carbon cycle. This disturbance, the study shows, is about 25 % larger and 100 million years older than the previously recognized disturbance. By finding that the carbon cycle 800 million years ago, prior to the first Neoproterozoic glaciations, was not operating as it is now, the team managed to constrain the onset of the new process in time and link it to the proposed "snowball Earth" event.
In their field work scheduled for this summer, the team will continue to investigate the disturbances to the Cryogenian and Ediacaran carbon cycles, and conduct research on the Tonian-Cryogenian-Ediacaran geologic, isotopic and paleogeographic history of northern Ethiopia and southern Australia. The geologists will then try to answer questions, such as what enabled the Cryogenian growth of ice sheets after a 1.5 billion year interruption.
