Posts Tagged ‘Colorado sand dunes’

The Sand Dunes of Colorado

Sunday, January 17th, 2010

Clorado Sand Dunes and Sangre Cristo Mountains

Clorado Sand Dunes and Sangre Cristo Mountains

The Great Sand Dunes National Monument is a national park in southern central Colorado. It gained national park preservation status in September 2004. It became a National Monument in 1932. The dunes rise from the floor of the San Luis valley to a height of some 750 feet ( 230 meters). This makes them the tallest sand Dunes in the United States. The dunes cover some 19,000 acres ( 77 square kilometers) and are at the base of the Sangre de Cristo mountains.

The sand came from the stream and lake beds of the Rio Grande and the tributaries that supply the river. Prevailing westerly wind currents over the last 12,000 years deposited the sand grain by grain as the wind rose to climb over the Sangre de Cristo Mountains.

There are few plants to hold the sand in place in this arid region so the dunes form and reform over and over again. Several streams along the perimeter of the dunes erode part of the dunes flow down stream. The arid conditions cause the streams to evaporate and the sand is blown back onto the dunes.

The dunes appear dry and on the surface they are but if you dig less than a foot into the dunes you will find wet sand. It is this underground wetness that keeps the dunes from blowing away. The underground water is one of the main reasons the park was formed. If the growing thirsty towns and cities bordering the park were allowed to channel off the water the dunes would rapidly disappear.

The color of the dunes varies from light tan to dark black. The black portion is made up of magnetite, a crystalline black oxide of iron.

Not all of the park is sand dunes. The park also contains alpine lakes and forests as you climb into the mountains. There are 6 peaks over 13,000 feet ( 3962  meters). There are stands of Spruce, aspen, and cottonwood.

Mendano creek is on the eastern border of the park close to the visitor’s center. The eroding sand causes the stream bed to be constantly changing and sand castle building along the streams banks is a favorite activity with park visitors. The sand falling in the stream causes small underwater dams to form then dissolve. This causes waves to form sometimes up to a foot in height especially during the spring runoff.

In Summer the sand can reach over 140 F ( 60 C). In winter it can snow. The closest city is Alamosa Colorado. The park became much larger in recent years after the federal government purchased 97,000 acres from the Baca ranch.

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