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Idaho Geology The Plateau Regions. Parts of the greater volcanic Columbia Plateau of Washington.

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Presentation on theme: "Idaho Geology The Plateau Regions. Parts of the greater volcanic Columbia Plateau of Washington."— Presentation transcript:

1 Idaho Geology The Plateau Regions

2 Parts of the greater volcanic Columbia Plateau of Washington

3 The Clearwater Plateau is the second region of Idaho formed like the Columbia Plateau Clearwater Plateau

4 Area drained by the Clearwater River, including the Palouse Hills

5 Tall rolling hills and gently sloping prairies A lot of it is ideal for farming for many reasons

6 Clarkston-Lewiston Moscow Post Falls Snake River Clearwater River WA ID Potlatch River Dworshak Clearwater and tributaries like the Potlatch

7 Snake River on border Clearwater joining from the east The Clearwater joins the Snake at the western edge of Idaho


9 Lowest point in Idaho – 738 feet at Lewiston

10 Originally formed by basalt flows

11 Granite peaks – Cottonwood Butte and Craig Mt.

12 Exposed as hills uplifted and basaltic lava eroded away

13 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.


15 Wheat farms of the Palouse with rich water- holding soil called loess

16 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)

17 Irrigation not needed because of clayey glacial loess

18 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

19 Palouse

20 Camas Prairie

21 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………

22 Pine forests

23 Owyhee- Bruneau Plateau 3 rd Volcanic region in Idaho

24 Rolling hills and mountains; dry and sparsely populated

25 Mountains Jump Creek Hills Poison Creek Hills French John Hills Owyhee Mts.

26 Rivers Owyhee River Bruneau River Jarbridge River Salmon Falls Creek

27 Bruneau Gorge

28 Columbia Plateau lava flows included Owyhee- Bruneau

29 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

30 2000-5000 feet above the SRP; some peaks rising to 8000 feet

31 WA, OR, CA ID Why is it so dry? Rainshadow Effect


33 Climate Extreme and semi-arid Precipitation 13-20 inches Summer average temp. = 88 degrees Winter average = 12 degrees

34 Southern Idaho Vegetation

35 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)



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