Great Sand Dunes National Park is a U.S. national park that covers 150,000 acres (about 600 sq km) in southwestern Colorado. The establishment of the park was authorized by Congress in 2004. A much smaller national monument, established in 1932, had previously existed in the same area. Great Sand Dunes National Park has the highest and tallest sand dunes as well as the largest dune field in North America. It is also noted for the tremendous range of ecological zones it contains and the multitude of wildlife species found there.
The heart of the park is the 30 square miles (about 70 sq km) of sand dunes in the main dune field. Star dune, the tallest of these, measures 750 feet (about 230 m) from the base to the very top. The dunes are made of sand left from prehistoric lakes that once existed in the San Luis Valley where the dune field is located. Winds in that area are funneled by the surrounding mountains in ways that build up and maintain the dunes.
Although the top few inches of the sand are normally dry, below that level there is persistent moisture. This allows animals and plants to thrive in a place where few would be expected to live. Temperatures at the surface of the sand can reach 140 to 150 degrees F (about 60 to 65.5 degrees C), while yearly lows can be as cold as -20 degrees F (about -29 degrees C.)
The dune field is surrounded by an area of sandy soil supporting both grasslands and a mixed juniper pinion pine scrub forest. To the west of the field the ground rises quickly into the Sangre de Cristo range of the Rocky Mountains. Six peaks over 13,000 feet (about 3,960 m) high stand within Great Sand Dunes National Park. The ecosystems present in the park run from the high desert of the dune field to the treeless alpine tundra at the top of the tallest mountains.
A huge range of animals are found within the park, including at least six insect species that are found exclusively in this area. Some of the amphibians and reptiles commonly seen there include Great Plains toads, bullsnakes and shorthorned lizards. Alpine lakes hold suckers, chub and several species of trout.
Mammals are very well represented in Great Sand Dunes National Park. Among the largest are bison, elk, and bighorn sheep. Mule deer and pronghorn are also present, as well as skunks, rabbits and raccoons. In addition to coyotes, predators in the park include black bears, foxes and mountain lions.