Geography of the Western United States: Mountains, Deserts, Forests, and Coasts

The American West — roughly the 17 states west of the 100th meridian — contains the continent's most dramatic topographic relief. From rainforests to sand dunes, 14,000-foot peaks to below-sea-level basins, it's a geologic sampler of planetary processes.

Mountain Systems: The Cordilleran Backbone

Rocky Mountains

• Extent: New Mexico → Mexico (Sierra Madre) — 3,000+ miles
• Key subranges: Front Range (CO), Wind River (WY), Tetons (WY), Bitterroots (ID/MT), Canadian Rockies
• High points: Elbert (14,440 ft), Whitney (14,505 ft — Sierra but geologically related), Rainier (14,411 ft — volcanic)
• Continental Divide: Runs crest — Atlantic vs. Pacific drainage

Sierra Nevada

• 400-mile tilted fault block — gentle west slope, sheer east escarpment
• Yosemite, Sequoia, Kings Canyon — glacial sculpture, giant sequoias
• Lake Tahoe: 1,645 ft deep, alpine jewel

Cascade Range

• Volcanic arc: Subduction of Juan de Fuca plate
• Stratovolcanoes: Rainier, St. Helens, Hood, Shasta, Lassen — active
• North Cascades: "American Alps" — rugged, glaciated, less volcanic

Coast Ranges & Basin and Range

• Coast Ranges: Parallel to coast — Franciscan complex (accreted terranes), redwoods north, chaparral south
• Basin and Range: Nevada, Utah, SE California — alternating fault-block mountains and valleys (Great Basin)
• Wasatch/Uintas: Utah — Wasatch Front (80% UT population), Uintas (E-W rare)

Deserts: Four North American Deserts Converge

Forests: From Temperate Rainforest to Ponderosa Parkland

• Pacific Northwest Temperate Rainforest: Olympic, Hoh, Quinault — 140+ in/yr, Sitka spruce, western hemlock, epiphytes
• Cascades/Sierras Mixed Conifer: Douglas-fir, ponderosa, sugar pine, white fir, incense cedar — fire-adapted
• Rocky Mountain Subalpine: Engelmann spruce, subalpine fir, whitebark pine (climate threatened)
• Pinyon-Juniper Woodlands: Great Basin, Colorado Plateau — 50M acres, expanding
• Coast Redwood (Sequoia sempervirens): Fog belt, 370 ft tall, 2,000+ years
• Giant Sequoia (Sequoiadendron giganteum): Sierra Nevada only, 300 ft, 3,000+ years, fire-dependent

Coastal Systems: Pacific Interface

• Rocky Coast (N. CA - WA): Sea stacks, tidepools, kelp forests, upwelling productivity
• Sandy Coast (S. CA): Littoral cells, submarine canyons, coastal squeeze (development)
• Estuaries: San Francisco Bay (largest), Puget Sound, Columbia River, Morro Bay
• Channel Islands: 8 islands — "Galápagos of North America", endemics
• Hawaiian Islands: Volcanic hotspot chain — 1,500 miles, 132 islands/atolls, unique biota

Water: The Limiting Resource

• Colorado River: 40M users, 7 states, 2 nations — overallocated, climate-stressed
• Columbia/Snake: Hydro (Grand Coulee), salmon, irrigation, barge
• Central Valley Project / State Water Project: CA plumbing — north→south
• Ogallala Aquifer: Fossil water — depleting (High Plains agriculture)
• Great Salt Lake / Salton Sea: Terminal lakes — shrinking, dust toxicity

The West isn't a region—it's a **collision zone** of tectonic plates, climate systems, and human ambitions. Its geography doesn't just shape life; it dictates the terms of survival.