Major North American river was missing for 5mn years. Scientists just solved the mystery of its disappearance

The Colorado River flows through the Grand Canyon and forms a 445-kilometre-long gorge that is about 6,000 feet deep. However, the river hasn't always taken this route. This happened only about 5-6 million years ago, but geological records show that the river existed in western Colorado roughly 11 million years ago. So, where was it for the first half of its life? Scientists have tried to answer this question for years and now finally have the answer. In a new study published in the journal Science, researchers say that the river flowed just east of the Grand Canyon to create a lake that is empty today. This extinct water body has been named Bidahochi Lake, but scientists do not know why it disappeared. Much of the deposits of this ancient lake have also eroded, making it hard to tell its peak and also which rivers fed it. To know more about this lake, the lead author of the study, University of California’s John He and his team checked for zircons in the samples of sandstones. Zircons are microscopic crystals that form in cooling magma and carry an accurate geochemical signature of the moment they were created.

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Finding the age and origin of zircons

Finding the age and origin of zircons was done by using lasers or ion beams to measure the ratios of uranium and lead isotopes, a process known as detrital zircon geochronology. This then helps trace the sources of a sediment and estimate when it was deposited. He said, zircons are like "little time vaults, and by looking at the age and geochemical signature of zircons, we can tell where a sediment that has been moved by a river originated." The team found that signatures of the sediments deposited in Lake Bidahochi roughly 6.6 million years ago were the same as those in other Colorado River deposits. They also found signs of rippling in rock layers and fossils of large fish species, hinting at the presence of fast-flowing waters, possibly a river that went into standing water.

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Colorado River flowed into a lake before it entered the Grand Canyon

This led the team to conclude that the Colorado River was feeding the Bidahochi Lake for millions of years before it started flowing through the Grand Canyon. The river at some point spilt over, an often-debated aspect about the water body. However, the new finding adds weight to the theory that the river did spill over at some point. The Colorado River is the biggest source of water for the American West, and is the lifeline of over 150 threatened species and more than 40 million people in the arid region.