The Grand Mesa is a large

mesa A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a ...

in western

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. It is the largest flat-topped mountain in the world. It has an area of about and stretches for about east of Grand Junction between the Colorado River and the Gunnison River, its tributary to the south. The north side of the mesa is drained largely by Plateau Creek, a smaller tributary of the Colorado. The west side is drained largely by

Kannah Creek Kannah Creek is a watershed that descends from the top of the Grand Mesa west southwest, where it meets the Gunnison River about 25 miles south of Grand Junction, Colorado. It offers many recreational opportunities, irrigation, and is an important ...

, which is received to the west by the lower Gunnison River. The mesa rises about above the surrounding river valleys, including the Grand Valley to the west, reaching an elevation of about . Much of the mesa is within

Grand Mesa National Forest The Grand Mesa National Forest is a U.S. National Forest in Mesa, Delta and Garfield Counties in Western Colorado. It borders the White River National Forest to the north and the Gunnison National Forest to the east. The forest covers most of ...

. Over 300 lakes, including many reservoirs created and used for drinking and irrigation water, are scattered along the top of the formation. The Grand Mesa is flat in some areas, but quite rugged in others.

Geology

The mesa is topped by a hard layer of volcanic basalt. This layer formed between about 10.9 and 9.6 million years ago, by the eruption of at least 27 separate lava flows from a vent in the Crag Crest area and probably other vents. This built up a maximum total thickness of more than of basalt. The resistant basalt layer suppressed erosion compared to the surrounding sedimentary rock layers, which suffered rapid downcutting from the action of the Colorado and the Gunnison rivers.Cole, R.; Weston, K. Geological Society of America Meeting Abstract (2007)
/ref> The top layer rests on a thick sequence of Eocene shale and sandstone known as the Green River and

Wasatch Formation The Wasatch Formation (Tw)Shroba & Scott, 2001, p.3 is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado.Cretaceous layer known as the Mesaverde Group that forms a cliff about halfway up the side of the mesa. The lowest layers are yellow and gray

Mancos Shale The Mancos Shale or Mancos Group is a Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States. The Mancos Shale was first described by Cross and Purington in 1899 and was named for exposures near the town of Mancos, ...

of late Cretaceous age. The shale continues outward into the surrounding valleys in the vicinity of the mesa, providing a

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

base that is fertile for various kinds of

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

, especially in the Gunnison Valley to the south. The flows of the Grand Mesa volcanic field may have originally covered an area of , but erosion has reduced the intact flows to just .

Climate

Climate on Grand Mesa varies by elevation. Higher elevations tend to be cooler and receive more precipitation. The top of the mesa is more than two miles above sea level, and experiences an alpine climate with substantial amounts of precipitation throughout the year. Because of the high altitude, summer days are mild, and temperatures drop sharply after sunset. Winter temperatures rarely rise above freezing, and can be extremely cold, often falling far below zero, especially at night. The top of the mesa is usually snow-free from late June through early October; however, the mesa receives heavy snowfall in the winter, rendering the forest service roads impassable. Accumulations of 20 or 30 inches of snow in the winter are typical. Surrounding areas with lower elevation are warmer and more arid throughout the year. The following climate data is for Mesa Lakes Resort, located on the north slopes of the mesa at 9,800 feet above sea level, which experiences a subalpine climate (

Köppen Köppen is a German surname. Notable people with the surname include: * Bernd Köppen (born 1951), German pianist and composer * Carl Köppen (1833-1907), German military advisor in Meiji era Japan * Edlef Köppen (1893–1939), German author and ...

''Dfc'').

Geography

The mesa is traversed by the Grand Mesa Scenic and Historic Byway, which includes SH 65, between the town of

Mesa A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a ...

on the north and the town of Cedaredge on the south. The route over the mesa provides a dramatic contrast in landscape, climate and vegetation. On the north side, the road climbs the steep terrain near the Powderhorn Resort ski area. The forested top of the mesa remains snowbound much later in the spring than the surrounding valleys, and is a popular location for cross-country skiing and snowmobiling. File:Cliff edge on Grand Mesa Colorado.jpg, Cliff edge on western face of the mesa. File:Field atop Grand Mesa, Colorado.jpg, Typical landscape on top of the mesa. File:Cattle atop Grand Mesa, Colorado.jpg, In the summer, cattle graze atop the mesa. File:Grand Mesa South.jpg, View from Grand Mesa looking south towards Island Lake and the

San Juan Mountains The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized (the Colorado Mineral Belt) and figured in the gold and silver mining industry ...

. File:Pond on top of Grand Mesa Colorado.jpg, Numerous ponds and small lakes dot the top of the Mesa. File:Fall Foliage Grand Mesa, Colorado.JPG, Fall colors atop the mesa. File:West edge of Grand Mesa, Colorado.jpg, Western edge of the mesa. File:GravelRoadGrandMesaColoradoSeptember2011.JPG, Typical Forest Service road atop the mesa. File:Looking towards Grand Junction Colorado from atop Grand Mesa Colorado.jpg, The view towards Grand Junction. File:Grand Mesa.JPG, An aerial photograph of Grand Mesa.

Geology

Climate

Geography

See also

References

Further reading

External links