A big chunk of the Earth’s crust is gone, but scientists think they’ve found it.
A mystery that puzzled experts for over a century was known as the “Great Unconformity” and referred to large slabs of Earth’s crust that were missing from the geologic record.
New evidence has shown that the extinction may have been caused by severe glacial erosion that occurred during a period when almost the entire planet was covered in ice.
The result is a gap in the sedimentary record, which occurs when the age of rocks suddenly changes due to the erosion of earlier rocks, which are then replaced by younger rocks.
The phenomenon was observed in 1869 at the Grand Canyon in Arizona. Experts noticed that the age of the rocks changed suddenly and found that this phenomenon was repeated in several places in the world, giving it the name of the Great Unconformity, writes Indy100.
A mystery that has baffled experts for over a century
The authors of one study were able to calculate that a global average of 3-5 kilometers of rock was removed by glacial erosion, leaving it “disappeared” from the record.
The study’s lead author, Dr. Brenhin Keller, of the Berkeley Geochronology Center, explained that the scale of rock loss is huge, estimating with his colleagues that a billion cubic kilometers of pre-Cambrian material is missing, based on what what should have been.
Their theory suggests that there was much more erosion that occurred before the start of the Phanerozoic era than experts originally thought, and they presented evidence showing that crystals from that era do, in fact, have hafnium and oxygen isotopes.
Their theory suggests that there was much more erosion
These isotypes are consistent with being eroded from older rocks and deposited at low temperatures.
Their theory also suggests that this is why there are many asteroid craters older than 700 million years and only two that are dated older than that.
As for the current location of the rock, it is claimed that the glaciers that eroded the sedimentary rocks also washed them into the sea.
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Source: www.descopera.ro
