Where did millions of years from the history of the Earth “evaporate”: A secret hidden underground
(ORDO NEWS) — In the mysterious rock formations known as “nonconformities” or unconformities, millions of years of Earth‘s history are simply missing. And science has an answer to this question.
Soil layers hold records of Earth’s history, and the deeper scientists dig, the further they “travel” into the past.
Think of the sheer, layer cake-like walls of the Grand Canyon in the United States that are often cited as illustrations of this process.
But not the entire surface of the Earth keeps the history of our world.
There are regions on our planet where no matter how much you dig, you will not find anything – hundreds of millions of years turn out to be “erased” or “unremembered” from history.
These gaps in the geological history of our planet, called “nonconformist”, exist in rock layers belonging to completely different time periods.
They sit on top of each other and are sometimes separated by more than a billion years. That is, roughly speaking, some forces somehow prevented the formation of precipitation for entire epochs.
These discrepancies are intriguing – a lost past, perhaps full of secrets about the evolution of the Earth and its life forms. But the gaps will also help scientists better understand our planet.
“The completeness of the picture depends on the Earth’s sediments, but in places they are fragmented, and huge sections have been lost to erosion,” said geologist Rebecca Flowers from the University of Colorado at Boulder.
“We need to understand the connection between surface processes (such as erosion) and deep processes, as well as biological, climatic and ecological ones.”
Flowers is the lead author of the study, which presents a new look at the “gaps” in the history of the Earth – the Great Disparity (nonconformity) that is visible (or, more precisely, not visible) in the rocks.
The gap stretches back to about 550 million years ago, and the era predates the emergence of complex life forms, to more than a billion years ago, when only microorganisms existed.
Previously it was thought that the layers were lost as a result of erosion, when snow and ice lay on the ground, between 715 and 640 million years ago.
But Flowers and her colleagues suggest that the “white spot” appeared as a result of “regional tectonic features.”
Scientists came to this conclusion by examining a disparity in a granite outcrop at Pikes Peak in Colorado.
But this is not the only place with lost records of the past. Great discrepancies formed at different times and for different reasons.
To understand the reasons for the gaps, the scientists examined samples of minerals and rock crystals – hematite and zircon, which can be used to restore the thermal history of the layers.
The results showed that the older rocks of Pikes Peak were eroded before snow and ice appeared, and therefore “could not have disappeared as a result of glacial erosion,” the researchers conclude.
Scientists have also cast doubt on the hypothesis that erosion associated with the Great Discontinuity could have provided Earth with nutrients, which led to the Cambrian Explosion – the sudden emergence of complex life forms about 541 million years ago.
“If the erosion occurred several hundred million years before the Cambrian explosion, this suggests that these events (the Cambrian explosion and the erosion of the Great Disparity) are not related,” explains Flowers.
“Our results indicate that at Pikes Peak, Colorado, the erosion of the Great Discontinuity formed several hundred million years before the Cambrian Explosion.”
Researchers believe that tectonic processes associated with the formation and breakup of Rodinia (a supercontinent that existed about a billion years before the snow era) may have caused the Great Discontinuity at Pikes Peak. But more research is needed to find out definitively.
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