A fragment of the first bark what did the earth have 4 billion years has just been discovered just below Western Australia. The ancient piece of land surface is the size of Ireland and is one of the oldest known, second only to the rocks of the Canadian Shield on the east coast of the hudsons baywhich are 4.3 billion years old (Earth formed 4.54 billion years ago).
The find, by a team of researchers from Australia’s Curtin University in Perth, is an important piece of the region’s geological history and will help explain how our planet evolved to become fit for life. The unusual discovery has been published in the journal ‘Terra Nova’.
As explained Maximilian Droellner, co-author of the study, something very special had to happen at that distant time: «when comparing our findings with existing data -he says- it seems that many regions of the world experienced a similar moment of early crustal formation and preservation. This suggests a significant change in the evolution of the Earth about four billion years ago, when the meteor bombardment subsided, the crust stabilized and life on Earth began to establish itself.”
asking the zircons
Geochemical clues in the sediments near this region, where some of the world’s oldest minerals have already been found, suggested there might also be remnants of an even older primitive crust buried under the newer surface rocks and sediments. So Droellner and his colleagues decided to analyze the zircons present in sediments from the Scott Coastal Plain, south of Perth.
In their work, the researchers used lasers finer than a human hair to target microscopic grains of zircons extracted from beach sand. As Droellner explains, the lasers were used to vaporize portions of individual grains of the mineral zircon, revealing where and when the grains were originally eroded. According to the scientist, the conclusion is clear: “There is evidence that a piece of crust the size of Ireland, up to four billion years old, has influenced the geological evolution of Western Australia during the last billion years and is a key ingredient of the rocks formed in the region throughout all this time.
The ancient crust covers an area of at least 100,000 square kilometers, the researchers write in their paper, and is buried deep below the surface. The ancient crustal boundary is associated with gold and iron ore deposits, suggesting the importance of this crust in controlling rock and mineral formation in the region.
Studying the formation of the crust 4 billion years ago can help researchers understand how the first continents formed. According to the study, this period set the stage for the planet to be as it is today, but few traces of the oldest Earth have survived the constant turmoil of the Earth’s surface.
“This piece of crust – concludes Droellner – has survived multiple mountain-building events between Australia, India and Antarctica and appears to still exist tens of kilometers deep under the southwestern corner of Australia.”