Geology of Idaho

The Snake River Plain

Idaho can be divided into 6 natural geologic regions, each

with its own unique characteristics

Northern Rockies

Clearwater

Plateau

Snake River Plain

Owyhee-BruneauPlateau

Basin & Range Province

Middle

Rockies

The Columbia Plateau spills over into other states from Washington, even into 3 regions of Idaho

Columbia Basalts show many layers from many sequential flows

Clearwater Plateau

Owyhee-Bruneau Plateau

Snake River Plain

These are the 3 regions of Idaho

that share a volcanic origin by extension of the

Columbia Plateau

Gently rolling hills and valleys; a thinly-spread grassland with some desert-like vegetation

Some cinder cones, erroneously called “buttes”, are located in this dry grassland

Rivers and their tributaries have left their impact on the plain

The Snake River is the main one, arising from Jackson Lake in Jackson Hole, WY, on the eastern

slope of the Grand Teton range

It flows westward across the southern edge of the SRP. Over thousands of years it has eroded huge canyons in some places, like the Snake River Canyon near Twin Falls (below)

On the eastern edge of the SRP is found the Grand

Canyon of the Snake River.

The deepest, most rugged part is called Hell’s Canyon, the deepest gorge in North America, 8000

feet below the surrounding mountain peaks

Hell’s Canyon lies at the foot of the Seven Devils Mountains (count them)!

Lewiston (L) and Clarkston (R) lie at the confluence of the Snake (back) and the Clearwater (bottom) Rivers

Lost River Range

• Lost River Sinks

The Lost Rivers flow out of the valleys of the Lost River Range and disappear into the ground of the Plain

The waters become part of the Eastern Snake River Plain Aquifer flowing to the Snake River on the west

The Snake and tributaries used to flood regularly through thousands of years

Now, dam systems control the flow

And create opportunities for agriculture

SRP Formation

• Volcanic activity

• Water erosion

• Sedimentation

Fissure flows

Leading to layered basalt formations

Numerous cinder cones

(buttes)

And every volcanic formation you can think of located at

Located in the east-central part of the plain in a triangular area

formed by Arco, Idaho Falls and

Pocatello

There are many self-

guided tours of the site as

well as an interpretive

center

pahoehoe Cinder cones

Aa

Lava tubes

The Yellowstone Hot Spot is responsible for the heat that created all this volcanism

Water is down in the summerdue to irrigation demands

Flooding is no longer a problem due to……

A series of dams to control flooding, create recreation, and provide

irrigation water

On June 6, 1976 the Teton Dam near

Rexburg, Idaho failed during its initial filling.  At 350 feet high, it was the largest dam break in US history and the damages reached $1

billion.

After the breach

This water has increased the value of the mixed volcanic-sediment soil to…….

Idaho Agriculture

Climate

• Mild and pleasant• Summers sunny and warm with few cloudy

days; winters cool and dry• Precipitation averages 10 inches (25cm);

semi-arid (quick thundershowers)• Summer temp.= 81degrees (105 max)

with cool evenings• Winter temp.=13-35 degrees with snow in

the mountains surrounding

From space

End of the road!