Lane County has a wide variety of land
surfaces, ranging from coastal plains to lofty, rugged mountains. Landforms include
shifting sand dunes, marine and river terraces, flood plains, estuaries, rugged headlands,
buttes, canyons, plateaus, glaciated valleys, lake basins, and volcanic cones and craters.
These land forms result from the balance between land forming processes, such as
volcanism, and destructive mechanisms, such as water channel erosion. Each of the four
major regions described below has its own special assemblage of these various surface
types.
The Coast Range
The Coast Range encompasses the entire western portion of Lane County, extending from the
Pacific Ocean to the Willamette Valley and abutting the Western Cascades south of the
Valley. The general level of the crestline is 1,500 feet, though many rounded ridges and
peaks are higher. Near the ocean beaches, shifting and stabilized sand dunes alternate
with marine terraces and rugged headlands. The interior is made up of many steep-sloped
hills and ridges incised by numerous perennial stream canyons. The Siuslaw River flows
through the region, draining a large portion of the range. Highways 126 and 36 both cross
the range on low, year-round passes.
The Southern Willamette Valley
The Willamette Valley is the only sizable humid lowland in Oregon, consisting of a broad
alluvial plain. From an elevation of nearly 430 feet at Eugene, the valley slopes gently
northward to the Columbia River. The slope is too gentle for good natural drainage.
Coupled with the accretion of river sediments, this low slope results in several
"yazoo" tributaries flowing parallel to the Willamette for many miles before
converging with the main channel. A number of small volcanic hills, such as Skinner's
Butte in Eugene, rise up to 300 feet above the valley floor.
The Western Cascades
The Western Cascades are a deeply dissected range of volcanic rocks much older than the
youthful High Cascades. Most of the surface consists of steep ridges running east-west
between the gorges cut by the upper courses and tributaries of the McKenzie and Willamette
Rivers. The range rises abruptly above the Willamette Valley and the ridges gain steadily
in elevation towards the east, with several mountains reaching nearly 6,000 feet.
The High Cascades
The High Cascades form the backbone of Oregon and constitute an imposing physical barrier.
The bulk of the range consists of a high lava plateau with numerous volcanic vents and
cones towering above it. The Three Sisters volcanoes, all extensively glaciated, reach
elevations over 10,000 feet. Lava flows and glacial processes have produced many small
lakes and a few large ones, most notably Waldo Lake. The Willamette and McKenzie Passes
both cross the Cascades in Lane County, but only the Willamette Pass remains open all
winter.
Clicking on the hyperlinks above will call up three dimnesional
perspectives of each physiographic region in Lane County.
