8.1: Introduction
This unit will cover two regions of the state, the Klamath Mountain, and Modoc Plateau provinces. To begin, the Klamath Mountains are a rugged and lightly populated mountain range in northwestern California and southwestern Oregon in the western United States. As a mountain system within both the greater Pacific Coast Ranges and the California Coast Ranges, the Klamath Mountains have a varied geology, with substantial areas of serpentinite and marble. Their climate characterized by moderately cold winters with very heavy snowfall and warm, very dry summers with limited rainfall, especially in the south. Because of the geology and soil types, the mountains harbor several endemic or near-endemic trees, forming one of the largest collections of conifers in the world. The mountains are also home to a diverse array of fish and animal species, including black bears, large cats, owls, eagles, and several species of Pacific salmon. Millions of acres in the mountains are managed by the United States Forest Service. The northernmost and largest sub-range of the Klamath Mountains are the Siskiyou Mountains.
The ecoregion, also known as a geomorphic province, was unglaciated during the Pleistocene epoch, when it served as a refuge for northern plant species. Its mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly volcanic rocks of the Cascades ecoregion to the northeast. The mild, subhumid climate of the region is characterized by a lengthy summer drought. It supports a mosaic of both northern Californian and Pacific Northwestern conifers and hardwoods.
As for the Modoc Plateau, it lies in the northeast corner of California as well as parts of Oregon and Nevada. Nearly 1,000,000 acres (400,000 ha) of the Modoc National Forest are on the plateau between the Medicine Lake Highlands in the west and the Warner Mountains in the east.
The overall landform is volcanic table land ranging from 4,000 to 6,000 feet above sea level, cut by many north–south faults. Occasioned lakes, marshes, and sluggishly flowing streams meander across the plateau. It is a thick accumulation of lava flows and tuff beds, along with many small volcanic cones. It has cinder cones, juniper flats, pine forests, and seasonal lakes. The plateau is thought to have been formed approximately 25 million years ago as a southern extension of the Columbia Plateau flood basalts.