Geologists: the first continents rose out of the water 700 million years earlier than thought the first continents rose above the water about 3.2-3.3 billion years ago – which is 700 million years earlier than previously thought. The article of scientists was published in the Proceedings of the National Academy of Sciences.
Geologists from Monash University, California Institute of Technology and Delhi University, using the uranium-lead method of radiocarbon dating, measured the age of zircon grains in the sandstones of the Singbum Craton, one of the most stable sites of an ancient tectonic plate located in the east of the Indian subcontinent. It turned out that these sandstones are the oldest rocks of this type on Earth: they formed about three billion years ago. This also suggests that the land that now constitutes the Indian Subcontinent had already appeared above sea level by that time. Sandstones of approximately the same age, scientists note, are present in the Australian and South African cratons – which indicates that the continents rose from the sea at about the same time. the craton formed at ever greater depths over the interval from 3.5 to 3 billion years. This indicates that the continental plates were getting thicker at this time. According to geologists' calculations, three billion years ago, the thickness of the continental crust of the Singbum Craton was already 50 kilometers – a sufficient level to float on the surface of the mantle and rise above sea level.