Landforms of Western North America: A Thematic Map Guide

Western North America—from the Pacific to the Rockies—is a collage of dramatic landforms shaped by tectonics, climate, and time. A thematic map reveals eight dominant provinces.

1. Coastal Plains

• Pacific Coastal Plain: Narrow, discontinuous—Olympic Peninsula to Baja. Marine terraces, estuaries, temperate rainforest.
• Gulf Coastal Plain: Extends from Texas to Florida—wide, flat, sedimentary.

2. Mountain Ranges (North-South Spines)

• Rocky Mountains: 3,000+ mi from NM to AK. Laramide orogeny (80–55 Ma). Continental Divide.
• Sierra Nevada: California's tilted fault block. Granite batholiths (Yosemite, Whitney 14,505 ft). Rain shadow creator.
• Cascade Range: Volcanic arc (St. Helens, Rainier, Shasta). Subduction of Juan de Fuca Plate.
• Coast Ranges: Parallel to coast (Olympics, Klamath, Santa Cruz). Accretionary prism + uplift.

3. Plateaus (Elevated Flats Between Ranges)

• Colorado Plateau: Four Corners. Layered sedimentary rock (Grand Canyon, Monument Valley). 5,000–11,000 ft.
• Columbia Plateau: WA/OR/ID. Flood basalts (Columbia River Basalt Group). Coulees, scablands.
• Great Basin: Not a single plateau but basin-and-range: horst/graben blocks (Nevada/UT).

4. Deserts (Rain Shadow & Subtropical)

• Mojave: CA/NV/AZ. Joshua trees. Death Valley (-282 ft).
• Sonoran: AZ/CA/Mexico. Saguaro cactus. Two rainy seasons.
• Chihuahuan: TX/NM/Mexico. High desert. Creosote bush.
• Great Basin: Cold desert. Sagebrush. Internally drained.

5. Forests

• Pacific Northwest Temperate Rainforest: Redwoods (CA), Douglas fir/cedar/hemlock (OR/WA/BC). High biomass.
• Montane Coniferous: Rockies, Sierra, Cascades — ponderosa, lodgepole, spruce, fir zones by elevation.
• Subalpine/Alpine: Krummholz, meadows, tundra above treeline.

6. Inland Basins (Closed Drainage)

• Great Basin: No outlet to sea. Terminal lakes: Great Salt Lake, Pyramid Lake, Mono Lake.
• Death Valley Basin: Lowest, hottest, driest. Badwater Basin.
• Salton Trough: Below sea level. Salton Sea (accidental, 1905).

7. Volcanic Features

• Cascade Volcanoes: Stratovolcanoes, lahars, lava tubes
• Yellowstone: Supervolcano caldera, geysers, hotspots
• Long Valley (CA), Valles Caldera (NM), Craters of the Moon (ID): Rhyolite, basalt fields

8. Glaciers (Relict & Active)

• Pacific Northwest: Mt. Rainier (25 glaciers), Olympics, North Cascades
• Sierra Nevada: Palisade, Lyell — shrinking rapidly
• Rockies: Glacier NP (26 left from 150), Wind River Range
• Alaska: Columbia Icefield, Juneau Icefield — largest in Americas

A thematic map doesn't just show lines—it tells the story of plates colliding, crust stretching, ice carving, and wind sorting. Western North America is tectonics made visible.