More than a billion long time of geological history is missing from parts of the Grand Canyon and , some geologists believe , much of the quietus of the human race . A new probe of this mystic spread in fourth dimension , which has puzzled geologists for 152 years , impute it to the break - up of the supercontinent Rodinia , 700 million years ago .
The tilt of northerly Arizona have been deposited over the last two billion years . The Colorado River has exposed these layers as it carved its way down , and therefore back in time . However , for much of the Canyon ’s length a Brobdingnagian wrapping is missing , with rocks from one era piled directly on top of those laid down much earlier , a characteristic known as an “ unconformity ” .
Unconformities are common , but the one the Grand Canyon exposes is so Brobdingnagian it was distinguish the “ Great Unconformity ” after being found in 1869 , and has perplexed geologists ever since . New evidence presented inGeologyoffers an account using remainder along the Canyon ’s length .
" The Great Unconformity is one of the first well - documented geologic features in North America , ” the appropriately name Barra Peak , a scholar at the University of Colorado , Boulder , said in astatement . “ But until recently , we did n’t have a batch of constraint on when or how it fall out . ”
The mystery has intensify with the discovery of other unconformities elsewhere in the public from the same era . Some geologists believe theseare connected , attributing them to the tremendous glaciation known asSnowball Earthscraping underlying rocks naked . Others think it’snothing morethan random event , some of which inevitably play off in meter .
Rodinia included most of the domain ’s continents , but separation begin around 800 million year ago and subsequently accelerated . Peak reason Rodinia ’s smashing divorcement produced a series of violent faulting events in the region around what is now the Canyon . Rocks were drag upwards and exposed to the element , eventually being washed to the ocean .
With so many geologists having studied the unconformity without reaching a conclusion , Peak require to do something different . She and her carbon monoxide gas - authors considered the fact that the pressure of superimposed layers wake rocks up , inducing chemical reactions that create a record of preceding temperature , a mental process love as thermochronology .
By measuring helium dispersion from ancient rocks , the generator concluded the eastern and westerly parts of the Canyon have quite dissimilar temperature story . Some 700 million years ago , as Rodinia was breaking up , the western basement rock was brought to the surface where it weather , but the eastern one-half remained bury 12 - 15 klick ( 8 - 10 mil ) cryptical .
Just how much prison term is overleap in the unconformity diverge , but near Lake Mead rock music 520 million eld quondam sit at once on top of stone 1.4 - 1.8 billion years sometime . “ There ’s more than a billion old age that ’s live , ” Peaksaid . “ It ’s also a billion age during an interesting part of Earth ’s story where the major planet is transition from an older scope to the modern Earth we know today . ”
Peak and colleague are now broadening their focus to other North American web site where the Great Unconformity can be see . Although the geological chance the Grand Canyon provides is hard to match , other position can indicate if what Peak observed was part of a widespread phenomenon .
