North Cascades National Park Geology

The North Cascades are still rising, shifting and forming. Geologists believe that these mountains are a collage of terranes, distinct assemblages of rock separated by faults. Fossil and rock magnetism studies indicate that the North Cascades terranes were formed thousands of miles south in the Pacific Ocean. Attached to slowly moving plates of oceanic rock, they drifted northward merging together about 90 million years ago.

Colliding with the North American Continent, the drifting rock masses were thrust upwards and faulted laterally into a jumbled array of mountains. The collision broke or sliced the terranes into north or south trending faults that are still evident today. Over time, these predecessors to today's North Cascades were further faulted and eroded to a nearly level plain.

During the past 40 million years, heavier oceanic rocks thrust beneath the edge of this region. Intense heat at great depths caused them to melt. Some of the melt rose to the surface as fiery volcanic eruptions like Mt. Baker. The rest recrystalized at various depths to form vast bodies of granitic rock forming the core of the North Cascades. These gigantic pinnacles have pushed upward to majestic heights again, exposing the roots of the ancient collision zone. Scientists agree North Cascades geology comprises some of the most complex and least understood geology in North America.

Glaciers / Glacial Features

Glaciers glisten as the most striking mountaintop feature of the North Cascades. Boasting over 300 glaciers and countless snowfields, the North Cascades National Park Service Complex is one of the snowiest places on earth and the most heavily glaciated area in the United States outside of Alaska.

Glaciers form when more snow accumulates in winter than melts or evaporates during the following summer. As the snow compacts into ice, it slowly moves downhill. As glaciers move, they gouge and scrape the land redefining the landscape. The North Cascades glaciers may be disappearing; most have shrunk dramatically during the last century. This is due to the combined effects of less precipitation and warmer summers, which most scientists now attribute to global warming.

Glaciers mirror the trends of climate change, resulting in life changes through soil development and distribution of vegetation. Glaciers are indicators of climate changes such as temperature and precipitation. As reservoirs of snow from past winters, pollutants may wash into mountain lakes and streams where they enter the food chain. Salmon and other aquatic life, along with plant and animal life could encounter difficulties as glaciers disappear.

Environmental Factors

The seemingly permanent and immovable mountains of the North Cascades are continuously rising as the landscape is shaped and reshaped by the environmental factors of the region: Water, Air, Earth and Fire.

Perhaps the most potent and abundant factor, water in its many forms, is at the heart of what makes the North Cascades the place of wonder that it is. As rain and snow it falls on the mountaintops where it is compacted into glacial ice that will carve its legacy in every stone. Eventually it melts, cascading down the mountainsides in rivulets that become streams that become rivers carrying the mountains bit by bit to the sea.

Air and Fire do their part as well. Winds whip through the valleys and whirl around the peaks invisibly shaping the land and the life upon it. Lightning strikes down out of the skies setting the forest alight. Small, weak trees and dead wood are burned to cinders making way for new life to spring forth from the ashes. And all three elements interact with the earth, shaping and molding it, using pieces of it;large chunks of stone dragged by a glacier or tiny pieces of silt adrift in the waterways;like a chisel to carve a new work of art from the land.

Humankind's mark does not go unnoticed either. Everything we do affects the park in ways both great and small; from our pollution to the non-native species we introduce to our efforts at preservation. Park scientists and policy makers work continuously to monitor these impacts and protect the natural wonder of the park.

Natural Features

Steep mountains coupled with an amazing variety of rock and water features contribute to the region's tremendous biodiversity. The mountains rise steeply to 9,206ft (2,806m) at Goode Mountain and fall to valley floors as low as 400ft (122m) along the Skagit River at the Complex's west boundary.

From the park's glaciers and over 300 lakes and ponds, flow thousands of miles of rivers and streams. Several major watersheds flow from the North Cascades including those of the Skagit, Stehekin and Nooksack rivers. The Skagit River and its tributary streams comprise the largest watershed draining into Puget Sound.

Variation in elevation, soil types, rainfall and exposure combine to form eight distinctive life zones from the lowland forests and wetlands to the alpine peaks and glaciers.

Rivers and Streams

In the heart of the forest, a hiker rests on a log stretched across a rushing stream. At water's edge, a newly emerged dragonfly tests its wings in the chill air. Just below the tumbling surface, young salmon leave their rocky beds to make their way downstream in search of the sea. In a myriad of ways, flowing water is the lifeblood and defining element of the North Cascades.

Major rivers continually shape the landscape on all sides of the Cascade Crest and provide key habitat for thousands of species of plants and animals. Nowhere is this more apparent than in the North Cascades. To the north, the Chilliwack River leaves the park to combine with the Fraser River in British Columbia (the largest watershed along the west coast of North America). The Nooksack River flows west beyond Mount Baker beginning its journey near Mt. Shuksan (the park's most photographed peak). Baker River drains the Picket Range and southeast slopes of Mount Baker joining the Skagit River, which flows from Canada, then westward across the middle of North Cascades National Park Complex. The Skagit is the largest watershed emptying into Puget Sound. In spite of the three dams along its length, the Skagit supports all five species of Pacific salmon and two anadromous (or sea-going) trout. The Stehekin River drains the southeast corner of the park to feed Lake Chelan - a glacier-carved trough which at 1500 feet is the third deepest natural lake in the nation. The waters of Lake Chelan eventually make their way to the mighty Columbia River, the largest river system in the western US.

These large rivers are fed by hundreds of streams with their origins in the steep mountains and glaciers. Late each summer these streams carry finely ground rock particles, or glacial flour, that cloud the water and lend a characteristic color. Local nicknames for the Skagit River include the Emerald Skagit and the Magic Skagit. The most dramatic contribution to this phenomenon is from Thunder Creek, which drains over fifty glaciers before flowing into the turquoise reflecting waters of Diablo Lake reservoir.

For the early peoples of this region the rivers were home, serving as means of transport, a key source of food, and clean drinking water. This still holds true today, and for the modern visitor the flowing waters of the North Cascades provide additional values of recreation, education, inspiration and hydropower.