The history of the formation of the Cascade Mountains dates back millions of years ago to the late Eocene Epoch. With the North American Plate overriding the Pacific Plate, episodes of volcanic igneous activity persisted. In addition, small fragments of the oceanic and continental lithosphere called terranes created the North Cascades about 50 million years ago.
The wilderness was originally designated the Alpine Lakes Limited Area in 1946, but this designation did not offer protection from resource extractions and was exclusively regulated by the United States Forest Service.
Over 2 million years ago, glaciation advancing and
retreating repeatedly scoured the landscape leaving deposits of rock
debris.
The last glacial retreat in the Alpine Lakes area began about 14,000
years ago and was north of the Canadian border by 10,000 years ago. The “U”-shaped cross section of the river valleys are a result of that recent glaciation.
Uplift and faulting
in combination with glaciation have been the dominant processes which
have created the tall peaks and deep valleys of the Alpine Lakes
Wilderness area.
Geology
The Alpine Lakes Wilderness features some of the most rugged topography in the Cascade Range with craggy peaks and ridges, deep glacial valleys, and granite walls spotted with over 700 mountain lakes. Geological events occurring many years ago created the diverse topography and drastic elevation changes over the Cascade Range leading to the various climate differences. These climate differences lead to vegetation variety defining the ecoregions in this area. The elevation range of this area is between about 1,000 feet (300 m) in the lower elevations to over 9,000 feet (2,700 m) on Mount Stuart.
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| Mount Stuart |
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| Intrusive Igneous |
The most common rock type in this area is intrusive igneous, which are highly fragmented granitics, this includes most of the Foss Lakes and Enchantment Lakes area. The other major rock types are sedimentary, metamorphics, ultrabasic rock complex and the extrusive igneous group that include basalt, andesite, and ryholite. The metamorphic rocks are primarily in the northern part and the southern area is made up of volcanic and sedimentary rocks. The Wenatchee Mountains are mostly composed of peridotite.
Ecology
The Alpine Lakes Wilderness is considered by the U.S. Environmental Protection Agency to be in the North Cascades ecoregion, dominated by forests, subalpine, and alpine ecozones. Indicator tree species of individual zones include the Western Hemlock, Silver Fir, Subalpine Mountain Hemlock, Subalpine Fir, and Grand Fir/Douglas Fir.
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| Western Hemlock |
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| Subalpine Mountain Hemlock |
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| Silver Fir |
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| Douglas Fir |
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The Alpine Lakes Wilderness offers an abundance of diversity in both
plant and animal species. The Alpine Lakes Wilderness and its old growth
forests offer critical habitat for many species on the Washington State
Department of Fish and Wildlife’s “Species of Concern” list which
includes:
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| Western Spotted Frog |
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| Townsend’s Big-eared bat |
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| Fisher |
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| Wolverine |
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| Lynx |
Alpine Lakes Wilderness has diverse wildlife, as well. Large mammals
such as black bear, elk, white-tailed deer, mule deer, cougar, and
coyote can be found throughout the region. Small mammals such as bobcat,
beaver, otter, badger, wolverine, mink, and weasel are also found in
sporadic populations. Grizzly bears and wolves are also found in the
region, but with still very small populations. Birds commonly seen
throughout the area include ruffed grouse, white-tailed ptarmigan,
Stellar's jay, ravens, chickadees, hawks, eagles, and woodpeckers. The
region is also home to multiple amphibian species of frogs and
salamanders, as well as multiple reptile species of lizards and garter
snakes. Various fish species of salmon and trout, including native
cutthroat trout, inhabit alkes, rivers, and streams within the area.
