North
Cascade National Park 
Required and recommended viewing and reading
|
 |
Figure 1. Annotated satellite image from Nasa Earth Observatory of North Cascade National Park, outlined in thin yellow line. Click on the image to view the park in detail. Ross Lake and Lake Chelan, south of the park, occupy glacial troughs scoured by valley glaciers. Mount Baker and Glacier Peak are stratovolcanoes.
Figure 1b. Google Map of North Cascade National Park. |
Facts: Area is 789 square miles. Established in 1968. Highest peak is Mt Shuksan (9131 ft, 2783 ft).
Description: Rugged mountainous landscape composed of Paleozoic through Tertiary metamorphic and igneous rocks. With 300 alpine glaciers the park has the highest concentration of glaciers than any other park in the conterminous U.S.
The glacially sculpted mountains of the North Cascade National Park contain no modern volcanoes. Although two towering volcanoes, Mount Baker and Glacier Peak, lie just beyond the park boundaries. The North Cascades are composed of a collage of Paleozoic and Mesozoic rocks (map) accreted to the Pacific Northwest and uplifted thousands of feet, a process that continues today. The park contains deep alpine valleys, high cirque basins and jagged aretes that were carved by Pleistocene and Holocene glaciers over the past two million years.
Exotic terranes in the North Cascades (See Domains of the Northern Cascades) include bits and pieces of volcanic arcs, oceanic deposits, oceanic crust, and microcontinent that were swept off the descending oceanic plate and transported to their present position along thrust and strike slip faults. In some areas tectonically mixed fragments of oceanic crust and sediment form a chaotically mixed unit called a melange--a characteristic creation of subduction. As more pieces were added, both the subduction zone and continental margin migrated westward. The exotic terranes are bound by faults and contain unrelated rock assemblages ranging in age for 570 Ma to 200 Ma. These rocks were later deformed and metamorphosed by pulses of compression and intrusive activity, the greatest occurring during the late Cretaceous. Unlike the mountains in the southern Cascades which are largely volcanic. Mountains in the North Cascades are carved from crystalline igneous and metamorphic rocks. Only Mount Baker and Glacier Peak are modern stratovolcanoes.
There are many reasons why glaciers are so numerous in the North Cascades. First is their proximity to the ocean and a westerly air flow that transports moist air to the mountains. Second, the air must rise over the mountains producing large amounts of orographic precipitation (~80 inches/year). Third, much of the precipitation falls during the winter months, often as much as 46 feet of snow. (See weather in the North Cascades) And forth, many peaks lie above the regional snowline (6500-7500 feet). Temperatures above this elevation are cool enough to retain snow and ice during the summer months. Examples of high glacial peaks are Mount Spicard (8979 feet), Mount Shuksan (9131 feet), Mount Challenger (8207 feet) - Picket Range, Mount Logan (9087 feet) and Eldorado Peak (8868 feet).
Sites to explore and references
Onto The Middle and Southern Cascades 
Lindley Hanson/Department of Geological Sciences/Salem State College/QkRef