London | Our planet’s first organisms may have formed in an ice cold ocean, according to a new study which suggests that the early Earth was much colder than previously believed. Many researchers believe that Earth’s early oceans were very hot, reaching 80 degrees Celsius, and that life originated in these conditions.
Researchers analysed volcanic and sedimentary rocks in the Barberton Greenstone Belt, in South Africa. The volcanic rocks were deposited at depths of 2 to 4 kilometres. We have found evidence that the climate 3.5 billion years ago was a cold environment, said Harald Furnes, a professor at University of Bergen in Norway.
The rocks analysed were formed at latitudes comparable with that of the Canary Islands. Some of the sedimentary rocks associated with the volcanic rocks, show a remarkable resemblance to those known from more recent ice ages. This may indicate that Earth, 3.5 billion years ago, experienced an extensive, perhaps global, ice age, Furnes said. Past ocean temperatures are measured by analysing the relations between oxygen isotopes in rocks known as chert, a rock composed of pure silicium-oxide.
These South African rocks have been exposed to high temperatures. Even so, this is related to hydrothermal activity, or springs of extremely hot water, pumped from the ocean bed. Additionally, the researchers found that these rocks had been exposed to cold water. By examining finely grained sedimentary rocks (originally a claylike mud), that exists along with the deep-submarine volcanic rocks, they found gypsum. Gypsum is produced under high pressure and at very cold temperatures, as in the present deep ocean.
In other words, we have found independant lines of evidence that the climate conditions at this time may have been quite similar to the conditions we have today, said Furnes. Some researchers may have difficulties accepting the new knowledge of an early, cold Earth, researchers said. A paradigm shift in Earth Science is not to be expected, but he thinks the climate of the early earth will be seen in a new light.