<P> Uplift associated with mountain formation later moved these sediments thousands of feet upward and created the Colorado Plateau . The higher elevation has also resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid . The uplift of the Colorado Plateau is uneven, and the Kaibab Plateau that Grand Canyon bisects is over a one thousand feet (300 m) higher at the North Rim (about 1,000 ft or 300 m) than at the South Rim . Almost all runoff from the North Rim (which also gets more rain and snow) flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon (following the general tilt). The result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side . </P> <P> Temperatures on the North Rim are generally lower than those on the South Rim because of the greater elevation (averaging 8,000 feet or 2,400 metres above sea level). Heavy rains are common on both rims during the summer months . Access to the North Rim via the primary route leading to the canyon (State Route 67) is limited during the winter season due to road closures . </P> <P> The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years, in part based on apatite (U-Th) / He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma . A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago . Previous estimates had placed the age of the canyon at 5--6 million years . The study, which was published in the journal Science in 2008, used uranium - lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon . There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus . In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years . However, this study has been criticized by those who support the "young canyon" age of around six million years as "(an) attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets ." </P> <P> The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet . </P>

When did the grand canyon start to form
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