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T252
Atlas Pg. 1,2

Coastal/Cascade Mts., California, Oregon, Washington
Volcanoes, lava flows, ash deposits, faults, glaciers, deforestation

Significance: The eruption of Mount St. Helens in May 1980 came as an abrupt reminder of the furnaces that lie beneath the entire Coastal and Cascade Ranges. Except for geologists, scarcely anyone in the "Pacific Northwest" was even dimly aware of the area's volcanic history though it is both active and recent. These mountains are, in fact, a highly volatile stretch of the Ring of Fire that encircles the Pacific Ocean. On the average, at least one major volcanic eruption has occurred every century during the last 10,000 years. Donald Peterson, a scientist with the Geological Survey, recently stated that "the sad truth is that we know very little about some of these (Cascade) peaks, and not nearly enough about any of them. We're only seeing part of one volcanic system here--we're trying to find out what goes on underneath the mountain by watching what happens on the surface. But if we are clever enough we will learn a great deal." The study of surface features on photos taken from the Shuttle's vantage point is an important contribution to increased geologic understanding of this potentially violent region of the United States.

Physical Characteristics: The Coastal/Cascade Ranges, north of the Sierra Nevada Range of California, extend from Northern California some 1100 km (700 miles) through Oregon and Washington into British Columbia where the Cascades fan out in an eroded tableland. The Cascades are geologically young mountains, formed atop the subduction zone where the Gorda Plate converges beneath the higher-riding North American Plate, off the Oregon and Washington Coast. About three million years ago, magma began rising to the surface through conduits to build this modern mountain system. The loftiest peaks of these ranges include the volcanic Mounts Ranier and Adams in Washington, Mounts Hood and Saint Helens in Oregon, and Mount Shasta in California. Also noteworthy is the spectacular Crater Lake in Oregon, which is the exploded heart of the former volcano, Mount Mazama. In the Northern Coastal Ranges are the Olympic Mountains, a rugged range west of Seattle, Washington. These mountains are characterized by alpine meadows, conifer rainforests, glaciers, lakes, and many streams. The western strip of the Olympic Mountains is in one of the areas of greatest precipitation in the United States with annual rainfall of 330.2 cm (130 inches), while the northeast side is one of the driest areas on the west coast. The mountains and hills and inland valleys of the Coastal/Cascade ranges are largely covered by forests, except at high altitudes. Glaciers are prominent on the higher peaks, especially Mounts Rainier and Hood. Deep river valleys, such as the Columbia River gorge between Oregon and Washington, cut through the mountains toward the Pacific Ocean.

Observation Techniques: Both near-vertical and oblique views of the mountainous areas will be useful for geologic studies. Near-vertical stereo photographs should be taken of the mountain peaks and volcanoes using the 250 mm lens. Photographs taken at different sun angles will be useful. Low oblique photographs along the valleys will aid in distinguishing variations in land forms, rock types, and vegetation patterns. CIR coverage is also desired.

Center Point: 44.5°N, 122.5°W