Deschutes Columbia Plateau

Happy New Year everyone! With this first article of 2010, I introduce eastern Oregon. East of the Cascades the landscape of Oregon changes dramatically from that of the western side of the state. The tall “Spine of Oregon” traps moisture on its western slopes, causing far lower amounts to fall on the east side. The result is a large desert, punctuated by a few mountain “islands” stretching to the border with Idaho.

Location

The Deschutes Columbia plateau runs north-south from the Columbia River to central Oregon, in the shape of a wedge that narrows the farther south one travels from the Columbia. At its widest point, the plateau's western boundary ends at the foothills of the east slopes of the Cascades. The eastern boundary extends to the foothills of the Blue Mountains. The southern end is more confined between the Cascades foothills and the Ochoco Mountains. This area is a smaller portion of the much larger Columbia Basin which includes Washington.

History

Taken from the Oregon Department of Geology and Mineral Industries (http://www.oregongeology.org/sub/learnmore/ColumbiaPlateau.HTM):

“Between 14 and 16 million years ago, "fissure" volcanic eruptions in eastern Washington, eastern Oregon, and western Idaho produced enormous volumes of molten Columbia River basalt that flowed like water west into the Deschutes-Columbia Plateau province in eastern Washington and northeastern Oregon, with some lava continuing to flow as far west as the Pacific Ocean via the ancestral Columbia River valley. As the basalt cooled and congealed, it formed the columnar cliffs that dominate the landscape today.”

Climate

The area is a high elevation desert (technically sagebrush steppe) that receives an average of 10 inches of precipitation per year (as compared to the Willamette Valley’s average of 40 inches). Winter snow, summer thunderstorms, and wind dominate this region. Temperatures can fall to below zero during the winter and soar to 110 during the summer.

Ecosystem

Despite the conditions, this desert, like most deserts, does have a thriving community of plants and animals. There are numerous species of birds and snakes. Three perennial rivers provide water for a variety of aquatic and wetland creatures. These “oases” in the desert only occur in narrow strips along the banks of the rivers but are home to many varieties of trees. Many parts of the plateau have been permanently altered due to farming and ranching. I have personally seen cows, sheep and horses in places you would not expect.

Human Activity

The plateau, because of its low annual rainfall and harsh temperatures, is used by humans mainly for ranching and farming. Agricultural farming is possible here due to irrigation from the Columbia, Deschutes and John Day rivers. Recently wind farming has become more popular as well. Recreational activities include hunting, camping, and rafting.

Things to See

The plateau is more sparse than regions I have discussed so far. However, even here there are places to see:

John Day Fossil Beds National Monument: http://www.nps.gov/joda/index.htm

Fossil, OR: http://www.cityoffossil.org/

Oregon Trail: http://www.nps.gov/oreg/index.htm

Recommended Reading: An excellent geologic paper detailing the plateau can be found here: http://www.wou.edu/las/physci/taylor/eisi/orr_orr2.PDF

If You Go: Be prepared for extreme temperatures during the summer and winter months. Thunderstorms during the hot season can lead to flash floods. Snakes are common, water is not. Some portions of the region are on private land, others are public. Be sure to bring a current map to avoid trespassing. The local BLM office in Prineville, OR can provide you with all the information you need before venturing into the back-country.

That's it for this month. There are four more regions in Oregon to explore. Beginning in June, and just in time for the summer outdoor season, I will focus on specific features in each of these geologic regions.

Original text © 2010 S. Skiles