Why are the cascades oriented north south

West-flowing and northwest-flowing streams have carved canyons as deep as 3, feet, measured from adjacent ridgetops to canyon floors. In contrast, the High Cascades subprovince is little eroded. This distinction arises for two reasons. First, broad uplift of the Western Cascades sometime after 8 million years ago created steep rivers that propelled erosional downcutting. Second, at about that time, volcanism was focused along the axis of the High Cascades, filling old canyons and building up the spine of the range.

The Western Cascades subprovince, with only sparse small volcanoes active in the past four million years, was spared the periodic infilling of its canyons by extensive volcanic deposits. Consequently, streams were able to erode unabated, deepening and broadening their courses and continuing to create relief in the Western Cascades.

The High Cascades in Oregon are coincident with the currently active volcanic arc, a nearly continuous band of large, long-lasting volcanic centers and smaller volcanoes, cinder cones, and lava domes. Nearly all of these have been active since four million years ago. To the casual observer, many of the smaller vents and volcanoes are merely bumps on the landscape. Better known are the prominent pinnacles of the glaciated shields or stratocones, such as Three Fingered Jack, Mount Washington, and Mount Thielsen and also the smoother slopes of the less-eroded Mount Bachelor and Mount.

But the crowning glories of the Oregon Cascades are the major volcanic centers— Mount Hood , Mount Jefferson, the Three Sisters, and Crater Lake, which sits in the caldera created by the eruption of Mount Mazama table 1.

These major centers are set apart by their longevity and overall size though not necessarily their present-day height. Volcanic activity at the major centers has persisted for many thousands of years, whereas the lesser volcanoes flare and go extinct more quickly, over spans of many months to centuries fig.

The major centers, with their longer life spans, develop diverse magmatic systems whose eruptive products can span the entire compositional range from basalt to andesite, dacite, and rhyolite. The hot subterranean environment for the long-lived centers is thought to host the major part of Cascade-related geothermal resources. In terms of morphology terrain aspects , the Oregon Cascade Range differs from that in Washington State.

In Washington, the active volcanic arc is composed chiefly of isolated large volcanoes that have been built on ridgetops of substantially older bedrock, amid deeply eroded canyons. In contrast, the volcanically active part of the Oregon Cascade Range is almost entirely young volcanoes along the entire chain. The major centers in Oregon are embedded in and superimposed on a broad constructional landscape composed of volcanic rocks thousands of feet thick.

The Oregon High Cascades presents, overall, a less rugged alpine landscape than its Washington counterpart. Numerous glacial episodes have iced over the Oregon Cascade Range during the past two million years. The most recent glacial maximum was about 20, years ago, when ice formed a continuous cap from north of Mount Jefferson southward to Mount McLoughlin. At that time, lobes of ice descended into the major river valleys along the west side of the range , reaching as low as 2, feet in altitude in the North Santiam and McKenzie River drainages.

Upon full meltback, ridges of debris outline the past extent of glaciers in the form of lateral and terminal moraines. One consequence is moraine-dammed lakes, such as Crescent, Odell, Cultus, Miller, and Suttle Lakes, all of them popular for fishing, boating, and swimming. For several millennia these glaciers have grown and shrunk in response to climate change.

The last episode of growth, referred to as the Little Ice Age, culminated in the late nineteenth century. Its ice advance was limited in extent and did not form a continuous ice cap, but it still left small distinct moraines poised above about 6, feet, just a few hundred feet below the toes of still-visible glaciers on the highest Cascade peaks.

Nothing divides a state like a major mountain range, and the Cascade Range has been a notable barrier. Moisture-laden air streaming from the Pacific Ocean cools as it ascends the west flank of the Cascades.

Cloud formation is a consequence—the well-known orographic effect—commonly leading to rain or snow. West-flank precipitation in the Cascade Range increases upslope to more than inches 3. This precipitation gradient persists but is less dramatic in the southern part of the Cascade Range, owing to storm paths but also because the Klamath Mountains part of the Coast Ranges expand the breadth and average height of the coastal mountains and wring more moisture from incoming weather systems than the lower and narrower Coast Range farther north.

Vegetation zones follow the precipitation patterns. Climax forest in much of the Western Cascades is western hemlock fig. In the southern part of the Western Cascades, with less precipitation east of the Klamath Mountains, the same longitudinal zone is characterized by needleleaf-broadleaf forest.

Upslope, each of these zones yields to subalpine forests of mountain hemlock, Pacific silver fir, and subalpine fir before passing into rocky alpine zones above the timberline. Downslope on the drier eastern flank, the Cascade Range vegetation is characterized by a forest zone of chiefly ponderosa pine fig. River capacity is another response to the orographic effect. For example, streams originating on the west flank of the Cascade Range, in their combined output, transport roughly ten times greater flow than east-flank streams.

West-flank streams in the southern part of the Oregon Cascade Range, such as the Rogue, South Umpqua, and North Umpqua Rivers, find their way directly to the ocean by cutting west through the coastal mountain system.

Farther north, however, by about the latitude of Eugene , westside Cascade streams begin coalescing into a single major river, the Willamette, which flows north into the Columbia. In many ways the Willamette River is a Cascade Range stream.

The Cascade tributaries to the Willamette have about four times the drainage area as Coast Range tributaries. Tributaries to this pair of rivers share a topographic divide just north of Chemult. On the Lower Curtis Glacier there is a dramatic increase in glacier speed and hence crevassing as the glacier slopes suddenly steepens a short distance above the terminus. Crevassses are formed by differential glacier speed, usually due to a change in glacier slope; hence they tend to occur in the same place on a glacier.

When a glacier flattens out crevasses are often compressed shut. Thus, a specific crevasse does not usually remain open as it is carried down glacier. Icefalls are regions of intense crevassing caused by a sharp increase in slope. The resulting glacier acceleration causes heavy crevassing.

Because of the comparatively rapid acceleration of the glacier, icefalls are unstable areas, having frequent avalanches. A prominent feature of icefalls are seracs. Seracs are towers of ice left standing between crevasses. The seracs often collapse causing numerous unpredictable avalanches during all seasons of the year.

Icefalls on the Coleman and Lower Curtis Glacier are the most easily observed icefalls on North Cascade glaciers, each displays prominent seracs. On slopes exceeding 55 degrees, glacier ice can no longer cling to the rock and will avalanche. These glaciers are spectacular to view from a distance, particularly during early spring when avalanching is heaviest, but are dangerous to set foot below. The avalanches end on gentler slopes, in some cases reforming into a glacier.

This type of glacier is a reconstituted glacier, Lower Park Glacier on Mt. Shuksan are reconstituted glaciers. That glaciers move makes them almost alive in our eyes. That this movement is unstoppable makes them daunting. There is no way to stop the inexorable motion of a glacier, in the Pamir Mountains of the Soviet Union an attempt was made to stop an advancing glacier by bombing it.

This failed, it was like bombing a sand dune, yes a large explosion occurred, but afterwards there was only slightly less snow and ice. In a similar fashion as glaciers slow down due to thinning from increased melting, we cannot offset this. On several glaciers in the Alps insulating blankets have been used to cover portions of several glaciers that are in ski areas. Because glacier movement increases with increasing thickness a glacier tends to moves fastest near the snowline where it is thickest, and slowest at the terminus where it is thin.

Movement has been measured on only a handful of glaciers in the North Cascades. The Columbia Glacier in the Monte Cristo area is more moves 20 feet per year. In this debris reached the terminus.

As climate warms a glacier will thin and move slower. In some cases velocities do exceed or even feet per year. In the icefall region above the terminus on the Lower Curtis Glacier the glacier is feet thick and is on an 18 degree slope. The result is a compartively rapid flow of feet per year. The fastest moving glaciers in the North Cascades are the large glaciers on the flanks of Mt. This high speed is due to the high thickness and consistently steep slopes on Mt. Baker glaciers. At the slow end of the scale is Colonial Glacier and Whitechuck Glacier each moving less than 5 feet per year.

The movement of glaciers has sculpted the North Cascades into the jagged alpine range they are today. During the last 2. The large valley glaciers carved out deep valleys, the expanded alpine glaciers carved out our alpine lakes.

Almost all alpine lakes in the North Cascades occupy cirque baisns excavated by glaciers. A cirque is a deep basin surrounded by high ridges in a horseshoe shape. These basins are created only by glacier erosion. The lip of the cirque, is the point from which stream emptying the cirque drains. The lip is near the former terminus position and has experienced little erosion; hence, the lip is higher in elevation than the area behind it where glacier erosion was high.

Glacier erosion being highest at the snowline, results in the basin being deepest approximately halfway from the cirque lip to the headwall. Glacier erosion is also rapid at the headwall of the cirque, hence a cirque eats away at the mountain that is at its head. On the eastern side of the range, grand fir, Douglas fir, aspen, and ponderosa pine are the dominant trees in the forests at the lower elevations, while whitebark pine and subalpine larch are the most common at the higher elevations.

On either side of the mountains, a wide variety of plants and vegetation, from ferns to flowering heather, can be found. More important, perhaps from a popular perspective, are the subalpine meadows or "mountain parks" that open up past the tree line. For many visitors, they are the high country's most characteristic feature.

The park's biological diversity extends to fish and wildlife, too. Native and introduced species of fish live in the park's lakes and rivers. Among the native fish are bull trout, cutthroat trout, and burbot; and among the introduced fish are rainbow and brook trout, and kokanee and Chinook salmon. The park's variety of habitats supports nearly species of wildlife. Sightings of deer, black bear, mountain goats, and various small mammals and birds are common, whereas encounters with mountain lions, coyotes, bobcats, grizzly bears, and wolves tend to be far less common.

Together these features -- mountains, glaciers, rivers, lakes, flora, fish, and fauna -- compose North Cascades National Park's principal natural resources. They are also the source for the popular perception of the park's quality as a "true wilderness" in a modern age and within such close proximity to the Puget Sound's metropolitan corridor. This focus on the park's wilderness resources has tended to obscure the human story of the range's past. The park's cultural resources are diverse.

The prehistory of the North Cascades, for example, reveals that perhaps within the last 5, years native people used the resources of the range on a seasonal and permanent basis. Similarly, studies suggest that the historic tribes of northwestern Washington, such as the Upper Skagit, Chilliwack, Lower Thompson, and Chelan, also exploited mountain resources traveling through the range's valleys and passes. In this respect, the North Cascades were thus not the unknown, impervious mountain range many whites of the nineteenth and twentieth centuries believed.

Evidence of Anglo American interaction with this rough landscape can be seen in the historic structures and sites that speak to early exploration, mining, homesteading, tourism, federal land management, and hydroelectric power development. Most of the activities associated with these structures were arduous undertakings. The range's extreme topography confined them to the major river valleys; they were transient in nature, and most left only reminders of their passing in silent mining operations and aging log cabins.

However, some pursuits left a more permanent mark on the region, such as the Stehekin community at the head of Lake Chelan and the dams erected by Seattle City Light on the Skagit River.

The wilderness of the North Cascades has not been an island in the stream of history, experiencing the occasional floods of interest. Here history has been, like the mountains, more a question of scale and perspective than magnitude. This administrative history has several purposes: to provide a summary of the park's thirty year development, to present a synthesis of the many issues that have concerned park managers from to the present, and to offer an analysis of North Cascades and its place within the history of the national park system and how the politics of its establishment and its wilderness mission distinguish it from other national parks.

This history is organized both chronologically and topically. The report is divided into three parts corresponding to three distinct eras in the park complex's history. In some cases, as with the discussion of the High Ross Dam controversy, this approach has been modified to provide better coverage of a topic. Within these sections, chapters address such recurring topics as administration, development, research and resource management, concessions management, hydropower issues, wilderness management, and land protection.

The first part addresses the establishment of North Cascades as a national park; the park movement spanned more than seventy years, and the compromises necessary to preserve North Cascades bear significantly upon the park's management.

The second and third parts reflect distinct eras of planning, and are divided into the park's first ten years and next twenty years. These sections essentially provide the context for the birth and growth of a relatively young national park and provide readers with a thematic framework with which to think of the park's management history. The park complex's first decade of administration can be characterized by the Park Service's attempts to carry out the legislative mandates of the North Cascades Act, develop the new park's management on a strong foundation of research, advance a strong commitment to wilderness preservation, and contend with the often contradictory aspects of traditional park management.

Stableisotope data and measurements of hot-spring heat discharge indicate that gravity-driven thermal fluid circulation transports about 1 MW megawatt of heat per kilometer of arc length from the Quaternary arc into Western Cascade rocks older than about 7 Ma millions of years before present.

Inferred flow-path lengths for the Na-Ca-Cl thermal waters of the Western Cascades are 10 to 40 kilometers km , and an average topographic gradient as large as 0.