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Borglum selected Mount Rushmore as the site for several reasons. The rock of the mountain is composed of smooth, fine-grained granite. The durable granite erodes only 1 inch (25 mm) every 10,000 years, indicating that it was sturdy enough to support sculpting. In addition, it was the tallest mountain in the region, looming to a height of 5,725 feet (1,745 m) above sea level. Because the mountain faces the southeast, the workers also had the advantage of sunlight for most of the day.
Though the area receives about 18 inches (460 mm) of precipitation on average per year, alone it is not enough to support the abundant animal and plant life. Trees and other plants help to control surface runoff. Dikes, seeps, and springs help to dam up water that is flowing downhill, providing watering spots for animals. In addition, stones like sandstone and limestone help to hold groundwater, creating aquifers.
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On 2009/01/10, Will said:
Feel free to post any comments or questions here. I will reply as soon as I am able.
Thanks for your time, and I look forward to hearing from you. -- Will.
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