below the seafloor, creating an amalgam of varied rock types formed at different times, by different means, and in different locations. In the process, tremendous pressures metamorphosed the deposits into uptilted and distorted strata of slate, quartzite, schist, gneiss, chert, and soapstone. Isolated pockets of unmetamorphosed sandstones, limestones, mudstones, and conglomerates can be attributed to later sedimentation and fallout from eruptions in a nearby volcanic chain. Geologists refer to this widely varied, complex, and mixed-up geology as the Klamath Knot.
There is no evidence of volcanic lava flows or eruptions with the Klamath Mountains. Granitic magmas did well up at various times, which accounts for the composition of most of the higher peaks in the area. Other igneous rocks, known as mafic and ultramafic, also squeezed up into faults and cracks in the earth’s crust; the high iron content of much of this rock accounts for the weathered red- and rust-colored rock of many of the other high peaks in the region.
Further upheavals, lateral movements, and constant erosion over geologic time gave many of the lower ridges and canyons much of the same shape as they display today, but the higher peaks and ridges received their final contours during periods of glaciation. Although these glaciers ran down the canyons just a few miles, the massive sheets of ice removed cubic miles of rock from the higher areas, depositing the ground-up rock in the lower areas. Once the glaciers receded, they left behind many small cirque-bound lakes at the heads of U-shaped valleys, with fantastically carved divides between them. Moraines dammed some of the larger valleys, which formed large lakes and marshes that eventually became some of the present-day meadows; Morris Meadows in the Trinity Alps is an outstanding example. Erosion distributed glacial till farther down the canyons, putting the finishing touches on the landscape that is visible today. Elevations in this part of the Klamath Mountains range from 900 feet along the lower Trinity River to 9,002 feet on top of Thompson Peak.
Many define three regions of the Trinity Alps by color as seen from the high summits of the central Alps. To the west is the extensive tract of land known as the Green Trinities, named not for a rock type but for the extensive swath of forest, perhaps the largest intact section of diversified forest in the greater Klamath Mountains. The Red Trinities includes lands of high ridgelines to the southeast that are defined by the characteristic igneous bedrock composed primarily of peridotite and interspersed with granite, which creates red-, brown-, and gray-colored summits. To the northeast, beyond the gash of Coffee Creek, are the granitic mountains of the White Trinities. The high, central Trinity Alps are also part of this group.
CLIMATE
Although the Klamath Mountains are much wetter than the Sacramento Valley and many other regions of Northern California, they are not nearly as wet as locations along the Northern California coast. Precipitation varies greatly in this relatively small area, from as much as 80 inches a year on some of the higher, west-facing slopes to less than 20 inches in some of the lower east-side canyons. Much of the precipitation occurs as either rain or snow during the winter months. However, thunderstorms are not uncommon during the summer.
Temperatures vary more greatly than along the coast or in the Sacramento Valley. Winter temperatures can be quite cold. Even Weaverville, at 2,000 feet, receives some snow almost every winter. The snowpack at the higher elevations can build up to 10–20 feet, making it an important storage facility of water for the Central Valley Project. High-country trails are usually free of snow by late June, but snow may linger all summer on north-facing slopes following winters of heavy snowfall.
Summer daytime temperatures can be quite hot, exceeding 90°F even at 5,000 or 6,000 feet. Down in the lower canyons, 100°F days are not uncommon. Day-to-night differentials can range up to as much as 45°F.
PLANTS
An amazing variety of plants grows within the Klamath Mountains. The varied geology, assisted by a relative lack of glaciation and volcanism, has produced one of the most distinct floral provinces in the world, which botanists refer to as the Klamath-Siskiyou Ecoregion. At the intersection of five major biotic regions—Coast Range, Cascade Range, Great Central Valley, Sierra Nevada, and Great Basin—the area boasts more than 130 endemic plant species and the highest concentration of different conifers in the world. The range harbors about 3,500 different plant species, including some unusual meat-eaters.
The most obvious members of the plant community are the trees. The forests in the Klamath Mountains are marvelously diverse and include some of the largest individuals of some species seen in the United States. Two unusual conifer species, weeping spruce and foxtail pine, are fairly common in the higher elevations, and rare elsewhere. Shasta red firs grow north of Redding, extending into southwestern Oregon.
The best way to categorize the forests and other flora of the Klamath Mountains is by plant communities. As in other mountain ranges, plant communities here are determined primarily by elevation. However, many other contributing factors, including soil type, rainfall, wind, and exposure, make the dividing lines rather indistinct. There is more intermixing of species between plant communities in the Klamath Mountains than in most other mountain ranges in North America. Descriptions of six very general plant communities follow.
Mixed Low-Elevation Forest This classification represents the low-elevation community up to about 3,000 feet, including isolated riparian (streamside) communities that may be found as high as 6,000 feet. The deciduous, broadleaf trees found here include alders, dogwoods, bigleaf maples, black oaks, hazelnuts, and Oregon oaks. Douglas-fir is overwhelmingly the most common conifer in this community, but lesser amounts of ponderosa pines and Jeffrey pines also appear, as well as sparse stands of Digger pines on lower, dry slopes. Evergreens other than conifers include madrones, chinquapin, tan oaks, California live oaks, and canyon oaks.
Some bushes appear as trees in the lower riparian areas, including coastal, red, and blue elderberries, along with ceanothus, dogwoods, hazelnuts, and manzanitas. Thick stands of chaparral extend over dry hillsides, with ceanothus and manzanita being the most common shrubs, and gooseberries, wild roses, and poison oak also present.
Poison oak grows in many forms, from low, spindly plants to tree-climbing vines, and is the bane of this plant community. Touching the plant produces a violent skin reaction in most humans and, when the plant is burned and the smoke inhaled, may cause serious poisoning requiring hospitalization. This noxious plant has shiny leaves in groups of three and is easy to identify and thereby avoid. The U.S. Forest Service (USFS) has some helpful information (available at ranger stations) that can help you learn to identify this plant.
Mixed-Conifer Forest The largest trees—sugar pines, ponderosa pines, Jeffrey pines, Douglas-firs, white firs, and incense cedars—grow in this zone between 3,000 and 6,000 feet. Vine maples and mountain ash are occasional associates to the stately conifers. Black oaks and alders are also found in the lower realms of this zone. These magnificent forests are found on most of the trails you’ll end up hiking in the Klamath Mountains.
Shrubs such as azaleas, raspberries, wood roses, and coast huckleberries carpet small openings in the forest. Pinemat manzanita and thimbleberries are common members of the understory. Large expanses of brush are uncommon at these elevations, but where they do occur, huckleberry oaks and other scrub oaks, which do not appear at lower elevations, are the principal plants.
Red-Fir Forest Red firs and their subspecies, Shasta red firs, occur almost equally in the Klamath Mountains between 5,000 and 7,000 feet. They often overlap considerably with conifers from the next lowest community, especially white firs. Slightly larger, beautiful cones distinguish Shasta red firs from the standard red firs, with longer bracts than scales, giving the cones a silver-flecked appearance.
At these elevations, western white pines begin to replace their close relatives, the sugar pines, while Jeffrey pines take over completely from their relatives, the ponderosa
