Idaho Geology
The Middle Rockies
Middle Rockies
Middle Rockies
• Ranges that are separated by broad valleys and plateaus (remember this description!). The ranges are the dominant features.
• Opposite description of Basin and Range
• Peaks in 8-10,000 ft. range
Geologic Origins• Folding for some ranges
• Faulting for some ranges (rows of fault blocks like B&R)
• Both folding and faulting for some ranges
Folding
Fault mountains may be simple horst and graben situations, or larger tilted fault blocks
Grand Tetons
Big Hole Mountains
Caribou Mountains
Blackfoot Mountains
Portneuf Mountains
Bear River Mountains
Mountain ranges
Blackfoot Mountains
Caribou MountainsGrey’s Lake in foreground
Portneuf Range
Bear River Mountains
Grand Tetons
Recognize this?
Blackfoot River
Portneuf River
Bear River
Gray’s River
Snake River
Teton River
Henry’s Fork
Rivers are important to this region
The Snake River begins in Jackson Lake, Wyoming, before flowing into Idaho
The first few miles in Idaho the river is actually Palisades Reservoir behind Palisades Dam, which controls floods and serves agricultural purposes (irrigation) as well as recreational needs (see next page).
Palisades Reservoir Palisades Dam
The Teton River flowing through Teton Valley
Henry’s Fork, one of the world’s premier fishing streams
Portneuf River
Blackfoot River Reservoir
Gray’s Lake
One of Idaho’s largest lakes, it is half in Utah
The Bear River drains the Middle Rockies around Bear Lake and the Bear River Mountains. It also drains the Eastern part of the Basin and Range
Soda Springs was so named because of large phosphate deposits discovered and
mined there even today.
Phosphate Mining
Phosphate Refining
• Baking reaction with sodium bicarbonate to produce carbon dioxide (CO2)
• Colas-Phosphoric Acid for fizz• Toothpaste-Dicalcium Phosphate Dihydrate as an
abrasive• Tooth Gels-Sodium Tripolyphosphate as a whitening
agent• Car Wash/dishwashing detergent-Sodium
Tripolyphosphate which softens water, removes soils and keeps soil from redepositing
• Fire Extinguishers-Mono- and Di- ammonium Phosphates as a fire retardant
• Latex Paint-Sodium Potassium Tripolyphosphate, Potassium Tripolyphosphate as a dispersing agent
• Fertilizers-Ammonium Phosphate as nutrient for plant growth
• Synthetic Rubber-Tetrapotassium Pyrophosphate as a catalyst
• Photocopier Toner-Tricalcium Phosphate as a dispersing agent
• Dyeing Wool-Diammonium Phosphate for control of pH in dye bath to allow even penetration of dye through the wool
• Explosives and pyrotechnics
Climate
• Fairly moderate and dry
• Summer average = 80 degrees
• Winter average low of 8 degrees
• Precipitation = 15” (at elevation)
• Snowfall heavy = 73” (at elevation)
• Rainshadow effect!
Rainshadow Effect
IDAHO
CASCADES AND SIERRA NEVADA
WASH/ORE
Vegetation
• Grassy valleys with irrigated farming between ranges
• Forested hills with most trees in moister low points
• Little vegetation on drier ridges
• Open forest encourages grazing/browsing
Towns and Cities
The End
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