There is a mystery lying deep within the Grand Canyon. One billion year old rock disappears. This has shaken the scientific community since it was first described nearly 150 years ago. Now, the mystery seems to be starting to be revealed.
"Like the red cliffs and the cliffs of the Grand Canyon as textbooks on Earth history. If we shrink the rock face of the canyon, we can jump back almost 2 billion years into the planet's past. But the book also loses some of its pages. In some areas, rock is worth more than 1 billion years has disappeared from the Grand Canyon, without a trace," said Barra Peak, a geologist at the University of Colorado, Boulder.
In a new study, researchers led by Peak identified a possible cause of the rock loss: the breakup of Earth's ancient supercontinent Rodinia about 700 million years ago. The upheaval was so intense that it likely swept rock and sediment into the ocean worth a billion years, in the case of the Grand Canyon.
The Great Unconformity was first described by John Wesley Powell during a boat expedition in 1869 along the Colorado River, which carved out Arizona's Grand Canyon. It was one of the first well-documented puzzling geological features in North America, according to the researchers.
Peak and his team completed an expedition like Powell's in the spring of 2021 and were greeted with the same boundaries between the Grand Canyon rock layers, which can be seen from the river. According to the researchers, at certain sites along the canyon, rocks aged 1.4 to 1.8 billion years were found lying beneath much younger 520 million year old rocks.
"There are beautiful lines. At the bottom, you can see very clearly that there are rocks pushed together. The layers are vertical. Then there are fissures, and above them are beautiful horizontal layers that form the buttes and peaks that are linked. with the Grand Canyon," explained Peak.
Peak and his team used a method called thermochronology to track the warming history of rocks to peer deep into the geological history of the Grand Canyon.
When a rock is buried deep underground, the massive pressure building on it causes the rock to heat up. This roasting, in turn, leaves traces of mineral chemistry behind the rock that reveal clues to the history of warming.
Peak and his team analyzed rock samples throughout the Grand Canyon and found the history of Great Unconformity may be more complicated than previously thought. The researchers suspect that the eastern and western parts of the canyon may have undergone different geological changes over time.
"This is not a block with the same temperature history," Peak said as quoted from Space.com.
According to the researchers, a series of minor fault events occurred when Rodinia, the supercontinent that preceded the more famous Pangea, broke up about 700 million years ago. Hard faults likely tore through the soil around the canyon, causing rock and sediment to be carried out to sea.
While the bedrock in the western part of the Grand Canyon appears to have surfaced about 700 million years ago, the same rock in the eastern part is buried under kilometers of sediment. The researchers predict that the upheaval may have torn apart the eastern and western portions of the Grand Canyon in different ways and at slightly different times, creating Great Unconformity in the process.
The team's findings helped gather information about what happened during this critical period for the Grand Canyon as well as other North American sites that have experienced similar periods of lost time.