Oregon covers a large and geologically varied area in the northwestern United States. It borders Washington to the north, California to the south, Nevada to the southeast, Idaho to the east, and the Pacific Ocean to the west. The Columbia River forms much of the northern border, while the Snake River defines much of the state's eastern boundary.
The state is often divided into several major physical regions:
- **Oregon Coast**: A narrow coastal strip with beaches, rocky headlands, estuaries, dunes, and coastal mountains. - **Willamette Valley**: The most populous and agriculturally productive region, lying between the Coast Range and the Cascade Range. - **Cascade Range**: A volcanic mountain chain running north-south through the state, including Mount Hood, Mount Jefferson, the Three Sisters, and Crater Lake's caldera complex farther south. - **Klamath Mountains and Southwest Oregon**: Rugged terrain with complex geology and biodiverse forests. - **Columbia Plateau and North-Central Oregon**: Basalt landscapes, river gorges, wheat country, and dry uplands. - **Basin and Range / High Desert of Central and Southeastern Oregon**: Arid plains, lava fields, buttes, closed basins, and sagebrush steppe. - **Blue Mountains**: Forested mountain systems in northeastern Oregon.
Oregon contains dense conifer forests, fertile alluvial soils, volcanic terrain, inland desert, and major river systems. Important rivers include the Columbia, Willamette, Deschutes, Rogue, Umpqua, John Day, Klamath, and Snake. Natural resources include timber, water, agricultural land, wind potential, fisheries, and mineral resources, though mining is far less central to the state economy than forestry and agriculture.
Geologically, Oregon is shaped by tectonic subduction along the Cascadia margin, volcanic activity, repeated flooding in prehistory, marine erosion on the coast, and large basalt formations in the east and north-central parts of the state. Climate varies sharply: marine west coast conditions dominate the coast, Mediterranean-like dry summers influence the Willamette Valley, alpine conditions prevail in high mountains, and semi-arid to arid climates characterize much of central and eastern Oregon.
