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The Grand Canyon is divided into two parts the North Rim and the South Rim. The South Rim is open all year and receives 90 percent of the park’s visitors. The South Rim has an airport and rail service and is also close to many transportation hubs and the Arizona cities of William and Flagstaff, as well as Las Vegas, Nev.
he North Rim is located closer to Utah and has stunning views, but is not nearly as accessible as the South Rim. While only 10 miles (16 kilometers) separate the two rims if you could walk across the canyon, it is only reachable by hikers who tackle the 21 miles.
Nearly 40 identified rock layers form the Grand Canyon’s walls. Because most layers are exposed through the Canyon’s 277-mile length, they afford the opportunity to study geologic evolution through time.
For thousands of years, the area has been continuously inhabited by Native Americans who built settlements within the canyon and its numerous caves. The Pueblo people considered the Grand Canyon ("Ongtupqa" in Hopi) a holy site and made pilgrimages to it.
Water seems to have had the most impact basically because our planet has lots of it and it is always on the move. Many people cannot understand how water can have such a profound impact considering that the Canyon is basically located in a desert. This is one of the biggest reasons that water has such a big impact here.
Because the soil in the Grand Canyon is baked by the sun it tends to become very hard and cannot absorb water when the rains to come. When it does rain the water tends to come down in torrents which only adds to the problem. The plants that grow in the Grand Canyon tend to have very shallow root systems so that they can grab as much water as possible on those rare occasions when it does rain. Unfortunately these root systems do nothing to deter erosion by holding the soil in place. Now you've got lots of water, no place for it to go, but down to the Colorado River, and nothing holding the soil and rock in place.
The result is frequently a flash flood roaring down a side canyon that can move boulders the size of automobiles, buses and even small houses. If automobiles, buses and small houses are in the way then it will take them too. Luckily no one builds houses in the Grand Canyon so that's not a problem but there are a few autos, vans and buses sitting at the bottom of the Colorado. This mass that moves down a side canyon during a flash flood is more like a fast flowing concrete than water and it can be very dangerous. You should always be well informed of weather conditions when you are hiking through side canyons in the Grand Canyon.