Phys.org has an interesting story about the Grand Canyon. The geologic record of the Grand Canyon spans about 2 billion years, but more than half of it is missing! This gap is known as the Great Unconformity. Now, a new study, published in the journal Geology, may have found evidence of what happened those missing rock layers.

Scientists have found evidence that a colossal cliff stretching thousands of kilometers across ancient North America may have exposed the heart of the Grand Canyon nearly a billion years before it was carved by the Colorado River.

The study, led by the University of Southampton in the UK, proposes that a vast “great escarpment” of steep rocky cliffs formed when the supercontinent Rodinia broke apart 800 million years ago.

Experts suggest the 1-kilometer-high (0.6-mile-high) cliffs extended along much of western North America, driving erosion of enormous volumes of rock and exposing an ancient crystalline basement now visible in the Grand Canyon in southern Arizona.

He added, “Our paper suggests the Canyon’s basement rocks were progressively brought to the surface as part of an immense escarpment that developed during the breakup of an ancient supercontinent.