Physical Geography of Washington State: Mountains, Water, Coast, and Islands

Washington State's dramatic landscapes result from tectonic collision, volcanism, glaciation, and maritime climate — creating seven distinct physiographic regions.

Mountain Systems

Cascade Range (North-South Bisector)

• Volcanic arc: Mount Rainier (4,392m, highest, most glaciated in contiguous US), Mount St. Helens (1980 eruption), Mount Adams, Glacier Peak, Mount Baker
• North Cascades: "American Alps" — jagged peaks, 300+ glaciers, North Cascades NP
• Rain shadow: Western slopes (200–500 cm precip) vs. Eastern (30–50 cm)

Olympic Mountains (Peninsula)

• Non-volcanic; uplifted marine sediments (basalt, sandstone)
• Mount Olympus (2,432m) — 60+ glaciers
• Hoh Rain Forest — temperate rainforest, 350+ cm rain, moss-draped maples
• Olympic National Park (UNESCO)

Other Ranges

• Blue Mountains (SE corner, extension of OR Rockies)
• Selkirk Mountains (NE, extension of Rockies)
• Willapa Hills (SW, low coastal range)

Major Rivers

Significant Lakes

• Lake Chelan: 81 km long, 453m deep (3rd deepest US), fjord-like, hydroelectric
• Lake Washington: 34 km, Seattle/Bellevue border, floating bridges (I-90, SR-520)
• Lake Roosevelt: Columbia reservoir (Grand Coulee), 217 km, recreation
• Lake Pend Oreille: ID border, 350m deep (5th deepest US), Navy acoustic testing
• Ross / Diablo / Gorge: Skagit hydro chain, stunning alpine setting

Pacific Coast (253 km)

• Rocky headlands, sea stacks, pocket beaches (Ruby, Rialto, Kalaloch)
• Olympic Coast National Marine Sanctuary
• Makah, Quileute, Hoh, Quinault tribal lands
• Columbia River bar — "Graveyard of the Pacific"

Islands

• San Juan Islands: 172+ named islands; ferry-served (Lopez, Shaw, Orcas, San Juan); orcas, kayaking
• Whidbey Island: 55 km long, NAS Whidbey, Ebey's Landing, Coupeville
• Vashon/Maury: Rural, ferry-only, arts community
• Fidalgo: Anacortes, ferry terminal to San Juans/Sidney BC

Eastern Washington Contrast

Columbia Basin: channeled scablands (Missoula floods), Palouse hills (wheat), Yakima Valley (apples, wine), Hanford (nuclear legacy), Tri-Cities.