| North Cascades | |
|---|---|
| Canadian Cascades | |
 Mount Shuksan, one of the most picturesque peaks of the North Cascades | |
| Highest point | |
| Peak | Mount Baker |
| Elevation | 3,286 m (10,781 ft) |
| Dimensions | |
| Length | 434.5 km (270.0 mi) North-South |
| Width | 241 km (150 mi) East-West |
| Geography | |
 Location map of the North Cascades and the Canadian Cascades | |
| Countries | |
| Province/State | |
| Parent range | Cascade Range |
| Borders on | Lillooet Ranges,Skagit Range |
TheNorth Cascades are a section of theCascade Range of westernNorth America. They span the border between theCanadian province ofBritish Columbia and theU.S. state ofWashington and are officially named in the U.S. and Canada[1] as theCascade Mountains.[2] The portion in Canada is known to Americans as theCanadian Cascades, a designation that also includes the mountains above the east bank of theFraser Canyon as far north as the town ofLytton, at the confluence of theThompson andFraser Rivers.
They are predominantly non-volcanic, but include thestratovolcanoesMount Baker,Glacier Peak andCoquihalla Mountain, which are part of theCascade Volcanic Arc.
The U.S. section of the North Cascades and the adjoiningSkagit Range in British Columbia are most notable for their dramatic scenery and challengingmountaineering, both resulting from their steep, ruggedtopography. While most of the peaks are under 10,000 feet (3,000 m) inelevation, the lowvalleys provide great local relief, often over 6,000 feet (1,800 m). The summits of the rest of the Canadian Cascades are not glaciated in the same way and feature rock "horns" rising from plateau-like uplands, with theManning Park andCathedral Park areas known for their extensivealpine meadows, as is also the case with the eastern flank of the US portion of the range. Portions of the US side of the range are protected as part ofNorth Cascades National Park.
The large amount ofprecipitation, much of it in the form ofsnow, and the resultingglaciation, combine with the regionaluplift to create a dramaticlandscape in the western part of the range. Deep,U-shaped valleys carved by glaciers inPleistocene time separate sharp ridges and peaks carved into steep shapes by more recent snow and ice.
The eastern and northernmost parts of the range are much more plateau-like in character, though in the case of the northernmost areas graven by deep valleys along the flank of the Fraser Canyon, notably that of theAnderson River.
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TheFraser River and the adjoining lowland on its south bank form the northern and northwestern boundary of the range. On the east, theOkanogan River and theColumbia River bound the range in the United States, while the northeastern boundary of the range departs the Thompson via theNicoamen River and runs via Lawless Creek, theTulameen River and Copper Creek to theSimilkameen River. On the west, the foothills of the range are separated by a narrow coastal plain fromPuget Sound except alongChuckanut Drive betweenBellingham andMount Vernon, where they abut the Sound directly.
The southern boundary of the North Cascades is less definite. For the purposes of this article, it will be taken asU.S. Highway 2, running overStevens Pass, or equivalently, theSkykomish River, Nason Creek, and the lowerWenatchee River. This roughly followsBeckey's geologic division inCascade Alpine Guide[3] and the definition used by Peakbagger.com.[4] Sometimes the southern boundary is defined bySnoqualmie Pass and the approximate route ofInterstate 90.[5] Sometimes the term "North Cascades" or "northern Cascades" is used for the entire range north of theColumbia River.[6]
Geologically, the rocks of the North Cascades extend south beyond Stevens Pass and west into theSan Juan Islands. The significance of the geologic transitions to theOkanagan Highland to the east and theInterior Plateau andCoast Mountains to the north are less agreed upon.[7]
Theclimate in the North Cascades varies considerably by location and elevation. The western slope of the range is wet and cool, with 60 to 250 inches (1.5 to 6.4 m) of precipitation per year. This produces atemperate rain forest climate in the low valleys, which then grades intomontane andalpine climates on mountain slopes and peaks. Summers are comparatively dry, with far less precipitation than in winter; sometimes the warmer eastern air and cooler western air meet at the Cascades during the summer months, and form thunderstorms. Sometimes, the storms move downwind into lowland cities.[8] The eastern slope lies in therain shadow of the range, since prevailing winds and most moisture come from the west, and hence is significantly drier than the western side of the main divide, becomingsemi-arid in the eastern lowlands.[9][10] As with most mountainous areas, precipitation increases dramatically with increasing elevation. As a result, there is a great deal of wintersnow andglaciation in the high North Cascades.
The eastern slopes and mountain passes can receive significant snowfall. Cold Arctic air can flow south fromBritish Columbia through theOkanogan River valley into the bowl-like basin east of the Cascades.Cold air damming causes this Arctic air to bank up along the eastern Cascade slopes, especially into the lower passes, such asSnoqualmie Pass andStevens Pass. The milder, Pacific-influenced air moving east over the Cascades is often forced aloft by the cold air held in place in the passes due to cold air damming. As a result, the passes often receive more snow than higher areas in the Cascades. This effect makes the relatively low elevation ski resorts at Snoqualmie Pass (about 3,000 feet (910 m)) and Stevens Pass (about 4,000 feet (1,200 m)) possible.[11]
The bulk of the North Cascades consists of "deformed andmetamorphosed, structurally complex pre-Tertiaryrocks".[12] These originated in diverse locations around the globe: the area is built of several ("perhaps ten or more") differentterranes of different ages and origins.[13] These terranes are separated by a series of ancientfaults, the most significant being the Straight Creek Fault, which runs north–south from north ofYale, British Columbia, throughHope,Marblemount, Washington, and down toKachess Lake near Snoqualmie Pass. There is evidence of significantstrike-slip movement on this fault in the past, with similar rocks on either side of the fault separated by dozens of miles. This is thought to be related to northward tectonic movement of the West Coast relative to the rest of North America.[14]
Since about 35 million years ago,oceanic crust from thePacific Ocean has beensubducting under thecontinental margin, which has formed the currentvolcanoes as well as a number ofigneousintrusions composed ofdiorite andgabbro.[14][15] The currentuplift of the Cascade Range began around 8 million years ago.[16]
Rocks similar to those in the North Cascades continue north to the vicinity ofMount Meager massif in theCoast Mountains, where they abut the Stikinia Terrane of the Omineca-Intermontane Province that dominates theInterior Plateau of British Columbia. This geologic similarity between the North Cascades and Coast Mountains results in a fairly arbitrary boundary between the two.
In British Columbia, the western geologic boundary of the North Cascades is defined as theFraser River as it follows the Straight Creek Fault, while in the United States the western boundary is defined by thePuget Lowlands in the west, although there are significant westward extensions of rocks similar in origin to those in the North Cascades found in theSan Juan Islands.[7]
The eastern geologic boundary of the North Cascades may be marked by the Chewack-Pasayten Fault. This fault separates the easternmost portion of the North Cascades, the Methow Terrane, from the Quesnellia Terrane, one of theOmineca andIntermontane Belts. The fault also separates theMethow River valley, part of the Methow Terrane, from theOkanagan Range, part of the Quesnellia Terrane. TheColumbia River Basalt Group bounds the North Cascades to the southeast.
The southern limit of what is geologically considered the "North Cascades" may variously be defined as being the southern limit of exposure of igneous and metamorphic terranes which is generally north of Snoqualmie Pass, Snoqualmie Pass itself, orNaches Pass at the White River Fault Zone.[7][17]
Whilealpine glaciers are a defining feature of the Cascade Range as a whole, this is especially true of the North Cascades. The stratovolcanoes (Mount Baker and Glacier Peak) are the most obviously glaciated peaks and have the largest glaciers, but many of the smaller, nonvolcanic peaks are glaciated as well. For example, the portion of the Cascades north ofSnoqualmie Pass (roughly the North Cascades as defined in this article) These glaciers all retreated from 1900 to 1950. From 1950 to 1975 many but not all North Cascades glaciers advanced. Since 1975 retreat has become more rapid with all 107 glaciers monitored retreating by 1992. 2015 was an especially damaging year for Cascadian Glaciers, an estimated mass loss of five to ten percent, the single greatest loss in over 50 years.[18] There are approximately 700 glaciers in the range, though some have already disappeared.[19] Since a brief advancing period in the 1950s, most of these glaciers have beenretreating. This is a serious concern towater managers in the region, as the glaciers (and the winter snowpack) form a large reservoir ofwater. As snow and ice melts in the summer, the resultingmeltwater compensates for the seasonal decrease in precipitation. As glaciers retreat they will provide less summer runoff.
The Cascades north of Snoqualmie Pass have 756 glaciers covering 103 square miles (270 km2) of terrain. For comparison, the entirecontiguous United States has about 1,100 glaciers in total, covering 205 square miles (530 km2).[20]
The North Cascades has a diversity of plant species.[21] It contains more than 1630vascular plant species[22] There are eight distinctlife zones that support thousands of plants separately and in their own way.[22] Traveling west to east through the range, one would intersect a number of distinct ecoregions, first getting higher and colder, then getting warmer, yet drier. Each of these component ecoregions can be described by either a treeindicator species, or by a lack of trees:Western hemlock,silver fir, subalpinemountain hemlock,Alpine tundra,subalpine fir, andgrand fir/Douglas-fir.[23]
The range also has a rich diversity of animals, includingbald eagles,wolves,grizzly bears,mountain lions andblack bears.[21] The range is home to at least 75 species of mammals and 200 species of birds that either pass through or use the North Cascades for a breeding area. There are also 11 species of fish on the west side of the Cascades.[21] Examples of amphibian species occurring in the North Cascades include thewestern toad (Bufo boreas) and therough-skinned newt (Taricha granulosa).[24]
The biodiversity of the area is threatened byglobal climate change and invasiveexotic plant species.[22] These exotic plants thrive by utilizing manmade structures such as roads and trails.[22] These invasive plants include thediffuse knapweed (Centaurea diffusa) andreed canary grass (Phalaris arundinacea).[25]
On the United States side of the border, early inhabitants of the North Cascades included theNooksack,Skagit, andSauk-Suiattle tribes on the west, and theOkanagan people on the eastern side, with theNlaka'pamux people of what is now Canada claiming hunting territory in the heart of the range, south across the border into Washington. The tribes living and using the range on the Canadian side of the border are theNlaka'pamux,Sto:lo and theUpper andLower Similkameen subgroups of the Okanagan. A now-extinct group known as theNicola Athapaskans also inhabited and hunted in the area now occupied by the Similkameen. Many current geographic names in the region are derived from native terms, either by transliteration or translation. Beckey notes that "Many names were derived fromChinook Jargon, mostly applied by theUnited States Forest Service from 1910 to 1940...."[26]
Fur traders entered the area in the first half of the 19th century, coming fromCanada and fromAstoria on theColumbia River. One of the earliest wasAlexander Ross of theNorth West Company, who crossed the range in the summer of 1814, probably viaCascade Pass.[27] The period of uncertainty surrounding the disputedOregon Country gave way following partition along the 49th Parallel to a period of tentativeU.S. Army exploration in tandem with violent subjugation of Indian tribes on the American side of the frontier in the second half of the century. With the partition, theHudson's Bay Company was forced to seek an alternative to its olderBrigade Trail via theOkanogan River and the construction of a new route over the northern spine of the Canadian Cascades from the area ofSpuzzum into the valley of theColdwater River to connectfort Langley on the lower Fraser with its northern posts inNew Caledonia. The route was impracticable and was soon abandoned, though more southerly routes through what is nowManning Park laid the foundations for later routes such as theDewdney Trail and the modernCrowsnest Highway viaAllison Pass, and was later similar to a route via theCoquihalla Pass for itssouthern mainline. South of the boundary, reconnaissance for possiblerailroad routes (none of which were viable north of the one eventually put in over Stevens Pass, at the southern edge of the North Cascades) and various mining rushes.
Miners dominated the exploration and development of the range from the 1880s through the early 20th century. For example, mines around the boomtown ofMonte Cristo, in the southwest portion of the North Cascades, produced "between $1 and $2.7 million in silver and gold".[28] TheHolden Mine, on the east side of the main divide, produced 106,000 tons of copper and 600,000 ounces of gold.[29] Discovery of gold by American prospectors on the banks of theThompson River at its confluence with theNicoamen River, at the northern tip of the range, helped trigger theFraser Canyon Gold Rush of 1858–1860 which in turn prompted the declaration of theColony of British Columbia to affirm British possession of territories north of the 49th Parallel. The Fraser rush led to exploration of the Cascades to the east of the canyon and in the valley of theSimilkameen River, with minor rushes in the area ofPrinceton, British Columbia in 1859 through the early 1860s and the creation of non-native towns (on top of much older native ones) atBoston Bar,Lytton andHope, as well as Princeton.
Early settlers also arrived in the foothills of the North Cascades in the latter half of the 19th century, and utilized the range in a limited way as a source of timber and grazing land. The range is so rugged that this exploitation was less dramatic than in other more gentle landscapes.
Early recreational use of the range included expeditions by the localclimbing clubs,The Mountaineers andThe Mazamas. These groups did not fully explore the inner reaches of the range and ascend the most difficult peaks until the 1930s and 1940s. It was not until the 1970s, that most peaks were climbed in the most isolated areas, making it one of the last explored ranges in the contiguous United States.[citation needed]
The North Cascades are often referred as the "American Alps" by hikers, climbers and mountaineers because of the sea of steep, jagged peaks that span across the range. This range's rugged approaches and exceptional alpine terrain make it a premiere training ground for mountain climbers.[30]
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