Download - Idaho Geology The Plateau Regions. Parts of the greater volcanic Columbia Plateau of Washington
The Clearwater Plateau is the second region of Idaho formed like the Columbia Plateau
Clearwater Plateau
Clarkston-Lewiston
Moscow
Post Falls
Snake River
Clearwater River
WA ID
Potlatch River
Dworshak
Clearwater and tributaries like the Potlatch
Snake River on border
Clearwater joining from the east
The Clearwater joins the Snake at the western edge of Idaho
Much of the region formed by wind and water erosion. Covered by a thick layer of rich topsoil of eroded volcanic
material mixed with clay-like glacial sediment blown in from Puget Sound (loess). This makes up the Palouse Hills.
Clearwater Climate
• Fairly mild
• Summer temp. averages 89 degrees with cool evenings
• Winter temp. averages 26-31 degrees
• Precipitation 20+ inches (25-55 in higher elevations)
• 4-6 month growing season! (the Banana Belt)
• The grasslands originally covering much of the region have now been generally replaced by domesticated grasses (wheat, oats, barley) and legumes (alfalfa, peas, lentils)
• Crop rotation and fallow fields help offset the loss of nutrients and water
• At higher elevations through the plateau and as the plateau in the east rises to meet the Rockies, evergreen forests are found. These are mainly………
Lava layers from the many preceding
fissure flows
Owyhee-Bruneau becoming a plateau through uplifting forces. This is the main difference
between it and the Snake River Plain
Climate
• Extreme and semi-arid
• Precipitation 13-20 inches
• Summer average temp. = 88 degrees
• Winter average = 12 degrees
O-B Summary• Hostile environment and
climate
• Ranching is main industry
• Low population density (more cows and sheep than people)
• Few towns
• Murphy is the county seat of Owyhee County (pop. 600)