Billion-Year Geologic Record Gap: Grand Canyon's Great Unconformity Possibly Due to Rodinia's Breakup

The Grand Canyon is one of the Seven Natural Wonders of the World and is a living history book. However, it has one billion years of missing geologic history. Dubbed as the Great Unconformity, this mystery gap is one of the largest missing pieces of 'time' in Earth's geology.

Now, Daily Mail reported that a new study by researchers from the University of Colorado reveals the complex missing history of the Grand Canyon.

The study titled "Zircon (U-Th)/He Thermochronology Reveals Pre-Great Unconformity Paleotopography in the Grand Canyon Region, USA," published in the journal Geology, theorize that the breakup of the supercontinent Rodinia might have triggered unconformities that shoved a millennium of rocks into the canyon's eastern ocean.

The Great Unconformity

According to Heritage Daily, the Great Unconformity was first identified in 1869 in John Wesley Powell's paper of the rock strata in Grand Canyon. Since then, several hypotheses have been made to explain the mysterious one-billion-year gap.

UC Santa Barbara geologist Francis Macdonald explained that there are unconformities throughout the rock record, and this one was thought to be a large gap.

Investigating the cause of the Great Unconformity is challenging, partly because it happened so long ago, and the planet is a messy system. Rocks in the Grand Canyon have been buried and eroded throughout history.

One hypothesis regarding the Great Unconformity was that glaciers scraped away kilometers of rock in an event known as Snowball Earth from 720 to 635 million years ago. This hypothesis also explains the rapid emergence of complex organisms shortly after the Cambrian explosion.

However, a recent explanation from researchers at the University of Colorado suggests that the breakup of the ancient continent of Rodinia from 630 million years ago caused strong earthquakes that set rocks into the eastern ocean of the canyon.

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Rodinia's Geological History Connected to the Great Unconformity

Supercontinent Rodinia formed a billion years ago, according to Daily Mail. However, between 750 and 633 million years ago, its fragments reassembled and formed the short-lived Pan-African supercontinent Pannotia.

That event has cooled the planet and led to the rapid evolution of primitive life during the Cambrian Period. Researchers believe that Rodinia's breakup is connected to the Great Unconformity and could shed more light on the matter.

"The Great Unconformity is one of the first well-documented geologic features in North America," Phys.org quoted lead author Barra Peak said. "But until recently, we didn't have a lot of constraints on when or how it occurred."

She added that the phenomenon makes beautiful lines that can be seen from the Colorado River. They used thermochronology, a method that takes the history of heat in the rock left by the pressure from geologic formations buried deep beneath the Earth.

Stone samples from the Great Canyon revealed that western and eastern parts have different heat histories, indicating that they went through different geological shifts throughout time.

During the breakup of Rodinia, the basement rock in the west seems to have risen to the surface while the eastern rocks were kilometers under sediment. Researchers believe that this difference is likely because of the Rodinia breakup that may have torn the eastern and western halves of the Grand Canyon.