Physical Geography of the US West Region

The American West is defined by dramatic topographic contrasts—tectonic, volcanic, and erosional forces on display.

Major Mountain Systems

• Rocky Mountains: Continental Divide backbone (Colorado, Wyoming, Montana, Idaho, NM). High peaks (Elbert 14,440 ft).
• Sierra Nevada: California's granite spine. Mt. Whitney (14,505 ft) – highest in contiguous US. Yosemite, Sequoia NPs.
• Cascade Range: Volcanic arc (WA, OR, N. CA). Rainier, St. Helens, Shasta, Hood. High precipitation.
• Coast Ranges: Parallel to Pacific. Olympics (WA), Klamath, Santa Cruz, Santa Ynez Mts.
• Basin & Range: NV, UT, SE CA, AZ. Alternating fault-block mountains & valleys (Death Valley, Great Basin).

Deserts

• Mojave: CA/NV/AZ. Joshua trees. Death Valley (lowest -282 ft, hottest).
• Sonoran: AZ/CA/Mexico. Saguaro cactus. Tucson, Phoenix. Bimodal rainfall.
• Great Basin: NV/UT/OR/ID. Cold desert. Sagebrush. High elevation.
• Chihuahuan: S. NM/TX/Mexico. Creosote bush.

Major Rivers

• Colorado River: 1,450 mi. Carves Grand Canyon. Lifeline for 40M people. Hoover/Glen Canyon Dams.
• Columbia River: 1,243 mi. PNW hydro powerhouse. Grand Coulee Dam.
• Snake River: 1,078 mi. Columbia tributary. Hells Canyon (deepest NA gorge).
• Rio Grande: 1,900 mi. TX/NM/Mexico border.
• Sacramento/San Joaquin: CA Central Valley drainage → Delta → SF Bay.

Notable Lakes

• Great Salt Lake (UT): Largest saline lake in Americas. Remnant of Lake Bonneville.
• Lake Tahoe (CA/NV): Alpine, deep (1,645 ft), ultra-clear.
• Crater Lake (OR): Deepest US (1,943 ft). Volcanic caldera. Intense blue.
• Lake Mead/Powell: Massive Colorado River reservoirs.

Forests

• Pacific Northwest Temperate Rainforest: Olympic, Hoh, Quinault. Sitka spruce, western hemlock. High biomass.
• Coast Redwoods (CA): Tallest trees on Earth (Sequoia sempervirens). Fog-dependent. Humboldt/Redwood NPs.
• Giant Sequoias (Sierra Nevada): Most massive trees (Sequoiadendron giganteum). General Sherman.
• Mixed Conifer / Ponderosa Pine: Rockies, Cascades, Sierra mid-elevations.