Olympic Mountains


The Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest summit at ; however, the eastern slopes rise precipitously out of Puget Sound from sea level, and the western slopes are separated from the Pacific Ocean by the low-lying wide Pacific Ocean coastal plain. These densely forested western slopes are the wettest place in the 48 contiguous states. Most of the mountains are protected within the bounds of Olympic National Park and adjoining segments of Olympic National Forest.
The mountains are located in western Washington in the United States, spread out across four counties: Clallam, Grays Harbor, Jefferson and Mason. Physiographically, they are a section of the larger Pacific Border province, which is in turn a part of the larger Pacific Mountain System.

Geography

The Olympics have the form of a domed cluster of steep-sided peaks surrounded by heavily forested foothills and incised by deep valleys. They are surrounded by water on three sides, separated from the Pacific by the wide coastal plain. The general form of the range is more or less circular, or somewhat horseshoe-shaped, and the drainage pattern is radial.
Rivers radiate outwards to all sides. Clockwise from windward to leeward, the major watersheds are: Satsop, Wynoochee, Humptulips, Quinault, Queets, Hoh, Bogachiel, Sol Duc, Lyre, Elwha, Dungeness ; and the Big Quilcene, Dosewallips, Duckabush, Hamma Hamma, and Skokomish.

List of summits

Principal summits:
Other summits:
A large portion of the range is contained within the Olympic National Park. Of this portion, 95% is part of the Daniel J. Evans Wilderness.
The national park is surrounded on the south, east, and northwest sides by the Olympic National Forest, with five wilderness areas, and on the southwest side by the Clearwater State Forest with one Natural Area Preserve, and the Quinault Indian Reservation. State parks and wildlife areas occur in the lower elevations.

Climate

Precipitation varies greatly throughout the range, from the wet western slopes to the semi-arid eastern ridges. Mount Olympus, nearly tall, is a mere from the Pacific Ocean, one of the steepest reliefs globally and accounting for the high precipitation of the area, with an estimated of snow and rain on Mount Olympus. of rain falls on the Hoh Rainforest annually, receiving the most measured precipitation of anywhere in the contiguous United States. Areas to the northeast of the mountains are located in a rain shadow cast by the mountain themselves, and receive as little as of precipitation around the city of Sequim. Annual precipitation increases to about on the edges of the rain shadow around Port Townsend, the San Juan Islands, and the city of Everett across Puget Sound. 80% of precipitation falls during the winter months. On the coastal plain, the winter temperature stays between. During the summer it warms up to between, with occasional hot spell days reaching to the upper 80s to low 90s °F.
The large number of snowfields and glaciers, reaching down to 1,500 m above sea level, are a consequence of the high precipitation, northern latitude, and cool moderating climate adjacent to the Pacific Ocean. There are about 184 glaciers and permanent ice fields crowning the Olympics peaks. The most prominent glaciers are those on Mount Olympus covering approximately. Beyond the Olympic complex are the glaciers of Mount Carrie and others in the Bailey Range, Mount Christie, Mount Queets, and Mount Anderson, however most of these have experienced significant decrease in both length and mass in recent decades, with several disappearing completely in the driest northeastern portion of the mountains. Due to global warming, glaciers in the Olympics are expected to largely disappear by 2070.

Geology

The Olympics are made up of obducted clastic wedge material and oceanic crust. They are primarily Eocene sandstones, turbidites, and basaltic oceanic crust. Unlike the Cascades, the Olympic Mountains are not volcanic, and contain no native granite.
Millions of years ago, vents and fissures opened under the Pacific Ocean and lava flowed forth, creating huge underwater volcanic mountains and ranges called seamounts. The Farallon tectonic plate that formed a part of the Pacific Ocean floor inched eastward toward North America about 35 million years ago and most of the sea floor subducted beneath the continental land mass of the North America plate. Some of the sea floor, however, was scraped off and jammed against the mainland, creating the dome that was the forerunner of today's Olympics. In this particular case, the future Olympics were being jammed into a corner created by the Vancouver Island and North Cascades microcontinents attached to the western edge of the North America plate. This is thought to be the origin of the curved shape of the Olympic Basaltic Horseshoe, an arc of submarine basalt running east along the Strait of Juan de Fuca, south along Hood Canal, and then west to Lake Quinault. Thrust-faulting northeast into the Vancouver Island/North Cascades corner pushes Olympic rock upward and southwestward, resulting in strata that appear to be standing on edge and that intermix with strata of different mineral composition. All this occurred under water; the Olympics began to rise above the sea only 10–20 million years ago.
The Olympics were shaped in the Pleistocene era by both alpine and continental glaciers advancing and retreating multiple times. The valleys of the Hoh, Queets, and Quinault rivers are typical U-shaped valleys carved by advancing alpine glaciers. Piles of talus and rockfall were created by retreating alpine glaciers. In the high mountains, the major rivers have their headwaters in alpine glacially carved cirques. During the Orting, followed by the Stuck, the Salmon Springs, and the Fraser glaciations, the vast continental Cordilleran Ice Sheet descended from Alaska south through British Columbia to the Olympics. The ice split into the Juan de Fuca and Puget ice lobes, as they encountered the resistant Olympic Mountains, carving out the current waterways and advanced as far south as present day Olympia. Ice flowed up the river valleys as far as, carrying granitic glacial erratics with it.

Ecology

The mountains support a variety of different ecosystems, varying by elevation and relative east–west location, which influences the local climate, primarily precipitation.

Flora

Olympic forests are coniferous forests, unique among mesic temperate forests in their almost complete dominance by conifers rather than by hardwoods. The hardwood:conifer timber volume ratio is 1:1,000 in the maritime Pacific Northwest.
Another unique feature of Olympic forests is the size and longevity of the dominant tree species. Every coniferous genus represented here is represented by its largest and longest-lived species, and some of its second and third ranked species as well. Biomass accumulations are among the highest in the temperate forest zones.
Dominance of conifers is thought to be a result of the amount and timing of precipitation. The dry summers limit the growth of deciduous trees, such as most hardwoods. Evergreens, such as most conifers, are able to take advantage of the winter precipitation by continuing to photosynthesize through fall, winter and early spring, when deciduous trees are not able to photosynthesize. No deciduous conifers occur in the Olympics; larch trees occur in the much-drier eastern Cascades, but not in the Olympics or western Cascades. There is only one species of evergreen hardwood, the madrone.
The great size and age of conifers here is thought to be a result of the relative lack of frequent windstorms like tropical cyclones.
Along the western flanks of the mountains the increased orographic precipitation supports temperate rain forests in the Quinault, Queets, Hoh, and Bogachiel river valleys at low elevations. Protection by Olympic National Park has allowed these rain forests to retain old growth trees, which supports a varied ecosystem. The Olympic rain forests are composed primarily of Sitka spruce and western hemlock, as are the surrounding lowland Sitka spruce forests, but are distinct in having a relative abundance of groves of bigleaf maple and vine maple, which support large epiphytic communities of mosses, lichens, ferns, and clubmosses; an abundance of nurse logs on the forest floor; a relatively open forest canopy and sparse shrub layer; and a dense moss layer on the forest floor. The rain forests are the wintering grounds for herds of Roosevelt elk and it is thought that browsing by the elk is responsible for the open shrub layer and the dominance of Sitka spruce over western hemlock.
The rain forests are just one type of forest found in the Olympic Mountains. Franklin and Dyrness set out 5 forest zones: Sitka spruce, western hemlock, silver fir, mountain hemlock, and subalpine parkland. Other authors include a sixth, Douglas-fir zone. Different plant associations are typical of one or more forest zones. For instance, the rain forest plant association described above is a member of the Sitka spruce forest zone.
The Sitka spruce zone is a lowland zone dominated by Sitka spruce and western hemlock. Precipitation is high, winters are mild, elevations are low. This forest zone is typically found at very low elevations on the western coastal plain and not in mountainous areas, although it can be found as high as.
The lower elevations of the Olympic mountains, from roughly up to –, feature the western hemlock zone, so-called because in most of the zone, the climax tree species would be western hemlock, even though much of the area is dominated by Douglas-fir. The reason for this is that Douglas-fir is an early seral species, and reproduces primarily after disturbances such as fire, logging, landslides, and windstorms. Western hemlock does not reproduce well on disturbed, exposed soil but germinates under the canopy of Douglas-fir, eventually overtaking the forest by shading out the Douglas-fir, which cannot reproduce in shade. In this zone, despite the high annual precipitation, drought stress in summer is sufficiently severe to limit growth of many species, such as Sitka spruce. Hardwoods such as bigleaf maple, willows, and red alder are limited to disturbed sites and riparian areas. red-cedar grows in the wettest sites. A very small area of the northeastern rain shadow contains the limited Douglas-fir zone, where it is too dry for western hemlock.
Moving up in elevation and moisture availability is the silver fir zone, up to about. This zone gets more precipitation, and more of it as snow, than the lower, warmer, drier western hemlock zone. The cold and the snowpack combine to limit growth of lower-elevation plants. On the other hand, silver fir is less drought tolerant and less fire tolerant than either Douglas-fir or western hemlock. Slide alder grows in snow-creep areas and avalanche chutes, along with yellow-cedar. Meadows of thimbleberry also grow in this zone, often intergrading between the slide alder chutes and the silver fir forest.
The next highest forest zone is the mountain hemlock zone, the highest forest zone in the Olympic mountains. In this zone most precipitation falls as snow and the snow-free growing season is very short. In the drier rainshadow side of the mountains, mountain hemlock is largely replaced by subalpine fir. At the higher elevations of the mountain hemlock/subalpine fir zone, tree cover is reduced to isolated stands of trees called tree islands, surrounded by subalpine meadows, in the subalpine parkland zone. Variations in substrate, topography, moisture, and snowpack depth and duration determine the vegetation community. Tree islands form on convex topography, which tends to gather less snow and shed it sooner than surrounding level or concave topography.
In the west, the subalpine zone is dominated by mountain hemlock. It occurs along with subalpine fir from in the Bailey Range; however, the range of this forest type is not extensive and does not extend much west of Mount Olympus, nor is it common in the east. Chamaecyparis nootkatensis|Yellow-cedar is sometimes found in relation to these plants. In the east and other drier areas, the subalpine zone is dominated by subalpine fir. It can occur with other trees, including mountain hemlock, silver fir, and yellow-cedar, but what characterizes these zones is the dominance of subalpine fir. These forests occur on the eastern ridges from.
In the Olympics, the treeline is between and but can be as low as under in some places. Treeline is a function of both elevation and precipitation, particularly the amount of snow that falls each winter. The growing season for trees is relatively short in the higher elevations of the windward Olympics, compared to similar elevations in other mountain ranges, due to the large accumulations of snow that take a long time to melt each year.
Subalpine meadows in the Olympic mountains are of 5 types. Heath shrub meadows are dominated by ericaceous huckleberries and heathers. Lush herbaceous meadows are typified by Sitka valerian and showy sedge. Drier areas or those with longer snow cover grow dwarf sedge or grass meadows. Phlox diffusa typifies the low herbaceous meadows of pumice, talus and scree slopes and other rocky areas. American saw-wort is common in both mountain meadows and lower subalpine parklands in the Olympics.
Above timberline is the Alpine zone, not a forest zone since no trees can grow this high. The alpine zone in the Olympics is much more limited in size than in other temperate mountain ranges, from to. The high precipitation of the Olympics creates permanent snow and ice at lower elevations than is typical for other mountain ranges, cutting off the alpine vegetation zone. Most of the alpine vegetation is on the rain shadow side, in the northeastern Olympics, where there is less permanent snow and ice. Alpine vegetation is low herbaceous, typified by Phlox diffusa and species of Carex. Many of the Olympic Mountain's endemic plants occur here, such as Piper's bellflower and Olympic violet.