A discovery may explain the Grand Canyon’s missing billion years

Researchers writing in the journal Geology propose that a roughly half-mile-high escarpment, stretching thousands of miles across ancient North America after the supercontinent Rodinia broke apart some 800 million years ago, may explain the Grand Canyon's missing billion years of geological record. As the cliffs eroded and retreated over tens of millions of years, they may have stripped away as much as 5 miles of rock in places, consistent with prior estimates of 3 to 6 miles lost before the modern canyon formed.

Lead author Thomas Gernon of the University of Southampton said the canyon holds rocks spanning roughly 2 billion years, though more than half that span is missing — a puzzle geologists call the Great Unconformity. The team combined plate-tectonic reconstructions with landscape-evolution modeling, comparing the ancient escarpment's position to modern examples in South Africa, Brazil, India and Antarctica.

The researchers say the vanished landscape may have also shaped river paths, sediment deposits and sea-level changes across the continent before the Cambrian explosion, when complex life diversified rapidly.

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