Geologists dig into Grand Canyon's mysterious gap in time

Pys.org ^ | August 19, 2021 | University of Colorado at Boulder

[BenLurkin]

Think of the red bluffs and cliffs of the Grand Canyon as Earth's history textbook, explained Barra Peak, lead author of the new study and a graduate student in geological sciences at CU Boulder. If you scale down the canyon's rock faces, you can jump back almost 2 billion years into the planet's past. But that textbook is also missing pages: In some areas, more than 1 billion years' worth of rocks have disappeared from the Grand Canyon without a trace.

It's a mystery that goes back a long way. John Wesley Powell, the namesake of today's Lake Powell, first saw the Great Unconformity during his famed 1869 expedition by boat down the rapids of the Colorado River.

The difference between those two types of rocks is significant. In the western part of the canyon toward Lake Mead, the basement stone is 1.4 to 1.8 billion years old. The rocks sitting on top, however, are just 520 million years old. Since Powell's voyage, scientists have seen evidence of similar periods of lost time at sites around North America.

Roughly 700 million years ago, basement rock in the west seems to have risen to the surface. In the eastern half, however, that same stone was under kilometers of sediment.

The difference likely came down to the breakup of Rodinia, a gigantic land mass that began to pull apart at about the same time, Peak said. The researchers results suggest that this major upheaval may have torn at the eastern and western halves of the Grand Canyon in different ways and at slightly different times—producing the Great Unconformity in the process.

[SunkenCiv]

LOL

[BatGuano]

I think that one of those rocks is resting on the shoulders of the p_resident in the white hut, JRBiteme!

[SunkenCiv]

The 'lunar origin' topics (the rest are listed in the last link below):

• Mysterious melting of Earth’s crust in Western North America, from BC, Canada to Sonora, Mexico [04/29/2021]
• Vast Fragments of an Alien World Could Be Buried Deep Within Earth Itself [03/25/2021]
• Astronomy Picture of the Day - Found on the Moon: Candidate for Oldest Known Earth Rock [02/03/2021]
• Explosive volcanoes ended Earth's time as a snowball: Huge eruptions broke our planet's deep freeze [01/18/2016]
• Meet 'Amasia,' the Next Supercontinent [02/09/2012]
• An Asteroid Trailing After Mars Could Actually Be The Stolen Twin of Our Moon [2020]

[wgmalabama]

Agreed.