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Tectonic Setting & Generalized Geologic Maps of Washington And

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Tectonic Setting & Generalized Geologic Maps of Washington And on the Lea rs din e g ch E a . d e . g T e Tectonic Setting & Generalized Geologic Maps of Washington and Oregon The TO TLE Pict Earthquakes ure Frank D. Granshaw and Jenda Johnson, 2009 Volcanoes Tsunamis Geology1 Physical Geography Legend for Geography Relief map of Washington and Oregon showing Map colors correspond to vegetation Generalized geologic map of the Pacific Northwest. major cities, volcanoes, lakes and waterways. and surface types: (Circled numbers are the same as on Physical Geography legend) Greens—dense vegetation 1 Browns—grasslands and desert 1 A A Light gray to white—unvegetated alpine regions in the Cascade Range 2 2 Cities A Bellingham, WA N La Grande, OR B Seattle, WA O Baker, OR B I C Tacoma, WA P Ontario, OR B I D Olympia, WA B Bend, OR E Aberdeen, WA R Klamath Falls, OR C H C F Ellensberg, WA S Medford, OR E D 3 F G Yakima, WA T Coos Bay, OR D 3 H Wenatchee, WA U Newport, OR I Spokane, WA V Astoria ,OR G J Walla Walla, WA W Portland, OR G K Pasco, WA X Salem, OR K 4 4 5 L The Dalles, OR Y Eugene, OR 5 V V M Pendleton, OR J J Cascade Volcanoes M M L L W W 1 Mount Baker 6 Mount Hood 6 6 2 Glacier Peak 7 Mount Jeerson N N 3 Mount Rainier 8 Three Sisters 4 Mount St. Helens 9 Newberry Volcano X X 5 Mount Adams 10 Crater Lake O 7 7 Legend for Geology U U Igneous Rock 8 8 Q Q Y Y P Volcanic (Less than 1.6 million years) Volcanic (More than 1.6 million years) 9 9 Volcanic (Mostly 16.5- to 6-million- year-old flood basalts) T T Intrusive rock 10 Sedimentary and Metamorphic Rock 10 Unconsolidated sediment Sedimentary rock S Sedimentary & metamorphic rock R S R Metamorphic rock Physiographic Provinces2 Tectonics3 Map of major physiographic provinces in the Pacic Northwest. Okanogan Relative motions of the crustal plates A physiographic province is characterized by terrain, rock type, geologic structure, and geologic history. North Cascades Highlands Range and distribution of Cenozoic volcanoes Coastal Mountains Olympic • Olympic Mountains and Coast Ranges—Folded and faulted Cenozoic marine sedimentary and volcanic rock. in the Pacific Northwest. The Cascadia Explorer • Klamath Mountains—Folded and faulted Mesozoic intrusive, sedimentary, and metamorphic rock. Mountains Plate Subduction Zone is the locked C a s Puget The Western Basins Lowlands boundary between the Juan de Fuca c • The Puget Lowlands—Broad marine embayment filled with Cenozoic glacial and fluvial (river) sediment. a d Paleozoic and Precambrian rocks exposed in places. i and overlying North American plates. a • The Willamette Valley—Broad river valley filled with Cenozoic sediment and occasionally exposed older volcanic rock. S Columbia Plateau u b Interior Mountain Ranges d Legend u • Cascades—Volcanically active range of Cenozoic lava flows and pyroclastic deposits. Peaks are <2 million years old. c Ridge t i • North Cascades—Younger peaks overlie Mesozoic and Paleozoic metamorphic, intrusive, and sedimentary rock. Juan de Fuca o • Okanagan Highlands & Blue Mountains—Folded and faulted intrusive, metamorphic, and sedimentary rock. Crustal Plate Boundaries Juan de Fuca n Precambrian through Cenozoic. Plate Z Blanco Fracture Zone o North American • Basin and Range—Actively extending north-south trending valleys and mountain ranges consisting n Convergent (plates are colliding) e of Cenozoic volcanic rock and lake deposits. Plate • Owyhee Uplands—A mountainous region consisting largely of Cenozoic volcanic rock. Divergent (plates pull apart) Blue Mountains Transform (plates slide past each other) Interior Plains and Plateaus Cascade Range Coast Range • The Columbia Plateau—A large plateau covering much of central Washington composed of thick layers of Willamette Valley Direction of relative plate movement Pacific Plate mid-Cenozoic flood basalts (16.5 to 6 million years ago). • The High Lava Plains—A high plain covering much of central Oregon, dotted with numerous Direction of movement of Juan de Fuca Gorda Cenozoic- to Holocene-age volcanoes. Plate High Lava Plain plate beneath the North American plate Gorda Ridge Volcanoes Cenozoic 65.5 million years to present Owyhee Mendicino Fracture Zone Mesozoic 251– 65.5 million years ago (dinosaur time) Major volcanoes TIME SCALE Klamath Uplands Paleozoic 542 – 251 million years ago Basin and Range Minor volcanoes Precambrian >542 million years ago Mountains 3 Schruben, P.G., Arndt, R.E., Bawlect, W.J., King, P.B., Beikman, H.M., 1994; Geology of the Conterminous United States at 1:2,500,000 scale—A Digital Representation of the 1974 P.B. King and H.M. Beikman Map. 2 Adapted from Orr, W., and Orr, E., 2002, Geology of the Pacific Northwest 1 Adapted from “Subduction and Volcanism” in Loy, W.G., Allen, S., Buckley, A.R, Meacham, J.E., Allen, S., Andreas, L.J., Martin, G.E., and West, R., 2001, Atlas of Oregon, University Oregon Press .
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