In South Africa, scientists have discovered traces of the most ancient glaciers
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Scientists have found traces of the oldest glaciers on the planet. They are located in South Africa, writes Science Alert with reference to Geochemical Perspectives Letters. Scientists discovered ancient rocks “beaten” by oxygen isotopes. They lie beneath the world’s largest gold deposits. A team led by University of Johannesburg geologist-archaeologist Axel Hofmann analyzed rock layers located near Durban on the east coast of South Africa. They contain glacial deposits estimated to be 2.9 billion years old, making them the oldest known on Earth. Photo: Getty Images The sequence of rock layers, called the Pongola Supergroup, has been largely undisturbed since it was formed many years ago by the inundation of an inland sea. “This is one of the few areas that has remained fairly intact and unchanged from the early Earth. These deposits are fossilized glacial moraines, which are basically debris left by a glacier as it gradually melts and contracts,” explains University of Oregon geologist Ilya Bindeman . A team of scientists measured oxygen isotopes and clay shales from the Pongola Supergroup. These samples have the lowest level of oxygen-18 among all similar deposits analyzed so far. And there is also a very high amount of oxygen-17, which indicates that the rocks were formed at lower temperatures. Oxygen isotopes are either “heavy” or “light”: it depends on the number of neutrons in their nucleus. So when geologists compare their relative abundance in ancient rocks, they can infer the conditions under which those rocks formed. Bindemann says that for this they had to form under the ice. “Combine this geochemical evidence with the moraine evidence and it means that these glaciers are the oldest glaciers found on Earth,” he added. According to preliminary estimates by scientists, global cooling occurred on Earth twice – 650 and 700 million years ago. But more and more researchers doubt that “the globe turned into a snow layer.” Bindemann and his colleague Hofmann are inclined to think that the continent that gave rise to South Africa was closer to the poles, so it was covered with ice. Read also: Astronomers have found a planet that resembles a giant mirror
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