North Cascades National Park
The U.S. section of the North Cascades and the adjoining Skagit Range in British Columbia are most notable for their dramatic scenery and challenging mountaineering, both resulting from their steep, rugged topography. While most of the peaks are under 10,000 feet (3,000 m) in elevation, the low valleys 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 the Manning Park and Cathedral Park areas known for their extensive alpine 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 of North Cascades National Park.
The large amount of precipitation, much of it in the form of snow, and the resulting glaciation, combine with the regional uplift to create a dramatic landscape in the western part of the range. Deep, U-shaped valleys carved by glaciers in Pleistocene time separate sharp ridges and peaks carved into steep shapes by more recent snow and ice.
Geology:
Named after the mountain peaks that are the central feature of the region, the North Cascades are a subsection of the Cascade Range which extends from northern California to British Columbia, Canada. The North Cascades are the northern section of the Cascade Range and unlike their southern counterparts, which consist mostly of Tertiary to Holocene volcanic rocks, the North Cascades are composed primarily of Mesozoic crystalline and metamorphic rocks. The exposed rocks which are found in North Cascades National Park predate the middle Devonian and are approximately 400 million years old. Much harder and more durable than the newer volcanic rocks of the southern Cascades, the North Cascades are consequently more rugged, with steep terrain being the norm due to heavy erosion from water and ice. Apparently still rising, the North Cascades originally formed from the jumbled masses of various rock structures that had their origination point thousands of miles to the south some 90 million years ago. By 40 million years ago, the heavier basaltic rocks of the ocean floor had started to push the lighter granitic rocks that are the core of the park’s mountains upward, a process that is ongoing. Continued rising in conjunction with erosion from water and ice has created deep valleys and consequently, the vertical relief is significant, averaging between 4,000 and 6,000 ft (1,200 and 1,800 m), which is comparable to much taller mountain ranges.