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Olympic Mountains

earth science Maturity 7-9 Next article →

The Olympic Mountains are a major mountain range located on the Olympic Peninsula. They sit in the Pacific Northwest region of the United States. These mountains are part of the larger Pacific Coast Ranges. They are spread across four counties: Clallam, Grays Harbor, Jefferson, and Mason. Most of the range is protected within Olympic National Park. Much of this park is also part of the Daniel J. Evans Wilderness.

OlympicMountainsWashington
OlympicMountainsWashington

The range has a unique circular or horseshoe shape. This shape creates a radial drainage pattern. In a radial pattern, rivers flow outward in all directions from a central point. The West Peak of Mount Anderson acts as the hydrographic apex. From this peak, rivers flow toward three different areas. Some flow west into the Pacific Ocean. These include the Hoh, Queets, and Quinault rivers. Others flow north into the Strait of Juan de Fuca. These include the Elwha and Dungeness rivers. Finally, some flow east into Hood Canal.

Mt. Anderson From East Fork Quinault Valley
Mt. Anderson From East Fork Quinault Valley

Geology explains how these mountains formed. They are not volcanic like the nearby Cascades. Instead, they are made of oceanic crust and clastic wedge material. This includes Eocene sandstones, turbidites, and basaltic oceanic crust. About 35 million years ago, the Farallon tectonic plate moved toward North America. Most of the sea floor subducted, or sank, beneath the continent. However, some of the sea floor was scraped off. This material jammed against the mainland to create a dome. This dome eventually became the Olympic Mountains. They began to rise above the sea 10 to 20 million years ago.

Climate in the range varies significantly due to the mountains' height. The western slopes are very wet. The Hoh Rainforest is the wettest place in the contiguous United States. In contrast, the eastern ridges are semi-arid. The mountains create a rain shadow effect. This means they block moisture from reaching the northeast. Areas like Sequim receive as little as 15 inches of precipitation. The mountains also host about 184 glaciers and permanent ice fields. Mount Olympus is the highest peak and has eight glaciers. However, many glaciers are shrinking due to global warming. Experts expect them to largely disappear by 2070.

The mountains feature several distinct forest zones. These zones change based on elevation and moisture. The Sitka spruce zone is a lowland area on the western coastal plain. It features high precipitation and mild winters. Below the mountains, the western hemlock zone is common. In this zone, Douglas-fir trees often grow first after a disturbance. Eventually, western hemlock grows under the canopy and shades them out. Higher elevations contain the silver fir and mountain hemlock zones. Finally, the highest areas consist of subalpine parkland.

The ecology of the Olympics is dominated by conifers. These are evergreen trees that stay green year-round. The ratio of hardwoods to conifers is only 1:1000 in this region. Conifers have an advantage because they can photosynthesize in winter. They use winter precipitation to grow while deciduous trees are dormant. The western rain forests are especially lush. They are filled with Sitka spruce and western hemlock. These forests also have many bigleaf maples and vine maples. These trees support large communities of mosses, lichens, and ferns.

Acer macrophyllum in Hoh Rain Forest
Acer macrophyllum in Hoh Rain Forest

Many animals and plants rely on these specific environments. Roosevelt elk live in the rain forests. Their browsing helps keep the shrub layer open. This allows Sitka spruce to remain dominant over western hemlock. The mountains also host unique plant life. For example, Piper's bellflower is an endemic species found only here.

Campanula piperi Piper's bellflower
Campanula piperi Piper's bellflower

The massive size of the trees is due to the lack of frequent windstorms. This allows for incredible biomass accumulation. The Olympic Mountains remain a complex and vital system of ecosystems.

Queets River Douglas-Fir
Queets River Douglas-Fir
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🖼️ Images & Media (7)
File:OlympicMountainsWashington.jpg
OlympicMountainsWashington.jpg
File:Mt. Anderson From East Fork Quinault Valley.JPG
Mt. Anderson From East Fork Quinault Valley.JPG
File:Acer macrophyllum in Hoh Rain Forest.jpg
Acer macrophyllum in Hoh Rain Forest.jpg
File:Queets River Douglas-Fir.JPG
Queets River Douglas-Fir.JPG
File:HurricaneRidge 7392t.jpg
HurricaneRidge 7392t.jpg
File:Campanula piperi Piper's bellflower.JPG
Campanula piperi Piper's bellflower.JPG
File:Olympic Mtings From Esquimalut, B C (HS85-10-39165).jpg
Olympic Mtings From Esquimalut, B C...
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