Researchers from Australia, India and the United States have shown that the first continents rose over the water about 3.2-3.3 billion years ago – which is 700 million years earlier than it was believed. The article of scientists is published in Proceedings of the National Academy of Sciences.
Geologists from the University of Monasha, the California Institute of Technology and Delian University with the help of a uranium-lead method of radiocarbon dating measured the age of zircon grains in Singbumian briefmarks – one of the stable areas of an ancient tectonic plate located in the east of the Indian subcontituent. It turned out that these sandstones are the ancient rocks of this type on Earth: they have formed about three billion years ago. This also suggests that land that is now the Indian subcontinent, by the time it has already appeared above sea level. Sandstones are approximately the same age, scientists note, in the Australian and South African cordon – which indicates that the continents rose from the sea at about the same time.
Researchers Analysis showed that the Granite rocks of the Singbum briefly for a segment from 3.5 to 3 billion years have been formed at all high depths. This suggests that the continental plates at this time became thicker. According to the calculations of geologists, three billion years ago, the thickness of the continental cortex of the Singbum briefly was already 50 kilometers – a sufficient level in order to swim along the surface of the mantle and rise above sea level.