Green River

300 million years ago, the area that now comprises the Colorado Plateau (the dominating feature of the Northern Southwest) was covered with ocean. The ebb and flow of this ancient ocean deposited considerable beach sands, marine limestone (calcium carbonate) and other minerals. Following the retreat of the oceans, the erosion of the Ancestral Rocky Mountains also added layers to the Colorado Plateau. Although the proto-Green and proto-Colorado Rivers did form at this time, it was not until 10 million years ago that the rivers began to cut their characteristic canyons. This accelerated erosion was caused by the uplifting of the Colorado Plateau.

Far below the dry plains of the Colorado Plateau, the ecosystem of the river basins and surrounding canyons is teeming with life. The most apparent vegetation along the rivers remains the tamarisk tree (also called Salt Cedar), which forms dense thickets along the river bottoms. Interestingly, the tamarisk is a native of South Asia, and was introduced to the United States for erosion and flood control. The tree’s ability to reproduce rapidly, recover after fire and hoard large quantities of ground water allow it to out-compete the native cottonwoods. In addition to trees, the river bottoms host a wide variety of cacti and other succulents. In the springtime, many species of cactus flower display a startling variety of red, pink and orange blossoms.

Many birds and other animals can also be seen along the river, including the Big Horn Sheep, Beaver, Canada Goose, Great Blue Heron, lizards and snakes. Also of note throughout the area is an interesting community of microorganisms that form patches of cryptogamic soil. These colonies of cyanobacteria form in thin sheaths across the desert floor, absorbing nutrients over hundreds of years. During rainy periods, they swell up to ten times their normal size. As they mature, other plants can grow through them symbiotically by enhancing the host’s root system and by tapping into plants’ roots for nutrients. These occur in patches of dark, spongy crusts in open areas. Take care not to step on them!

Suggested reading list:

Baars, Don. (1989) Canyonlands Country. Canon Publishers: Lawrence, Kansas.

Belknap, Bill., Belknap, Buzz. (1974) Canyonlands River Guide. Westwater Books: Evergreen, Colorado.

Belknap, Buzz., Evans, Laura. (1978) Desolation River Guide. Westwater Books: Boulder City, Nevada.

Belknap, Buzz., Evans, Laura. (1980) Dinosaur River Guide. Westwater Books: Evergreen, Colorado.

Cunningham, Richard L. (1990) 50 Common Birds of the Southwest. Southwest parks and Monuments Association: Salt Lake City, Utah.

Hoffman, John F. (1985) Arches National Park. Western Recreation Publications: San Diego, California.

Houk, Rose. (1992) Anasazi Prehistoric Cultures of the Southwest. Southwest Parks and Monuments Association: Tucson, Arizona.

Kelsey, Michael R. (1991) River Guide to Canyonlands National Park and Vicinity. Kelsey Publishing: Provo, Utah.

MacMahon, James A. (1988) Deserts. Alfred A. Knopf: New York, New York.

McPherson, Robert S. (1992) Sacred Land Sacred View. Brigham Young University/ Signature Books: Salt Lake City, Utah.

Niehaus, T., Ripper, C., Savage, V. (1984) Southwestern and Texas Wildflowers. Houghton Mifflin Company: New York, New York.

Noble, David Grant. (1995) Ancient Ruins of the Southwest. Northland Publishing: New York, New York.

Peterson, Roger Tory. (1990) Western Birds. Houghton Mifflin Company: Boston, Massachusetts.

Powell, J.W. (1961) The Exploration of The Colorado River and its Canyons. Dover Publications: New York, New York.

Stall, Chris. (1990) Animal Tracks of the Southwest. The Mountaineers: Seattle, Washington.

Stokes, Lee. (1969) Scenes of the Plateau Lands and How They Came to Be. Starstone Publishing: Salt Lake City, Utah.

Tweit, Susan J. (1994) The Great Southwest Nature Factbook. Alaska Northwest Books: Portland Oregon.

If you have other reading suggestions please let us know!