The Grand Canyon has long puzzled scientists with a puzzling geological mystery in some areas where more than 1 billion years of rock layers do not exist, as if they had disappeared without a trace.
This peculiarity was discovered in 1869 by geologist John Wesley Powell, while traveling down the Colorado River. Now, thanks to a team of American researchers, this strange gap in time known as ‘The Great Disagreement’ is closer to being understood after nearly 150 years since it was first described, according to a new study published in the journal Geology.
The reddish cliffs of the Grand Canyon are like an Earth history textbook, and climbing its walls can go back almost 2 billion years, but that book is missing pages, explained Barra Peak, from the University of Colorado Boulder and lead author of the work.
In some places, it seems that hundreds of millions of years simply never existed, as rocks that are 1.4 billion and 1.8 billion years old are found alongside rocks that are only 520 million years old.
An ancient supercontinent
The team thinks they have a clue to why. Suppose that a series of small but violent failures they may have rocked the region during the breakup of an ancient supercontinent called Rodinia. And the resulting ravages likely tore the land around the canyon, dragging rocks and sediment into the ocean.
For their research, the scientists used a method called thermochronology, which traces the history of heat in the stone. They explain that when geological formations are buried deep, the pressure that builds up on them can cause them to heat up. That heat, in turn, leaves a trace on the chemistry of the minerals in those formations.
After analyzing the samples collected in the picturesque area, they realized that the history of this feature can be more complicated than previously thought. In particular, the western half of the canyon and its eastern part – that which is most visited by tourists – may have undergone different transformations over time due to the Rodinia rupture.
While the findings are not enough to completely solve the mystery of ‘The Great Disagreement’, are an important step, and the researchers believe that the same techniques can be applied in other sites with similar geological characteristics.