As with the Oregon Coast Range as a whole, the Southern Oregon Coast Range likely began as an ocean island chain that collided with the continental tectonic plate of North America more than 60 million years ago. In the Southern Range the 64‑million-year-old Roseburg volcanics that formed this section are the oldest portions of the entire range. The range is part of a forearc basin that has slowly rotated about 51 degrees since the Eocene period. Much of the mountain structures are pillow basalt formations created during the volcanic period and then uplifted with the collision into the continental plate. Other geologic features are mainly the result of erosion and weather forces carving steam beds and valleys out of the rock formations.
Flora and fauna
The Oregon Coast Range is home to over 50 mammals, 100 species of birds, and nearly 30 reptiles or amphibians that spent a significant portion of their life cycle in the mountains. Birds living in the Southern Coast Range include a variety of smaller and larger bird species. These include northern goshawks, peregrine falcons, pileated woodpeckers, olive-sided flycatcher, and western bluebirds. The northern spotted owl, listed as a threatened species by the United States also inhabit the mountain forests. Aquatic life includes river lamprey, Pacific lamprey, coastal cutthroat trout, Millicoma longnose dace, Umpqua chub, red-legged frogs, southern seep salamander, western pond turtles, coho salmon, Chinook salmon, steelhead trout, and others. Other wildlife includes fringed myotis bats, long-legged myotis bats, Townsend's big-eared bat, fishers, and sharptail snakes, northern flying squirrels, red tree voles, Roosevelt elk, among others. Other small animals include shrews, moles, deer mice, and ermine. Plants include large stands of Douglas-fir trees, western hemlock forests, cedar trees, with portions of these forests including old-growth stands. Other flora include Sitka spruce, salmonberry, salal, tanoak, and western azalea. Portions of the range are in the Elliott State Forest.
Location and climate
The range begins around the Umpqua River with the Central Oregon Coast Range to the north. Oregon Route 38 is the general divide between the two sections. On the southern end the Coquille River’s middle fork provides the general dividing line between the Central Range and the Klamath Mountains to the south and east. The climate of the mountains is of the mild maritime variety. It is characterized by cool dry summers followed by mild and wet winters. Most precipitation falls in the form of rain, with snow during the winter months at the higher elevations. Annual precipitation varies from, with more in the higher elevations. The average high temperature in January is, and the average high in July is with temperature also varying by elevation.
Peaks
All peaks in the range are over in elevation.
Rivers
The following rivers have portions of their headwaters in the Southern Oregon Coast Range:
