Objectives for the topic: NW Washington from Ski to Sea (Mountain Building Processes)

Reading: Chapter 20 in Tarbuck and Lutgens

Images to understand: 4, 6, 7, 10, 11, 14, 15, 16, 17

After completing this topic, the student will be able to:

1. Explain that mountains are typically uplifted by three processes: folding, thrust faulting, and igneous activity.
2. Explain that mountains are typically formed at a convergent margin.
3. Sketch each of the following types of mountains: Aleutian, Andean, Himalayan.
4. Describe a terrane in the geologic sense.
5. Explain the roles of erosion and isostasy in exposing the roots of old mountain ranges at the surface.
6. Explain that the history of the northwest Cascades involves repeated terrane accretion, with folding and thrust faulting accompanying each event.
7. For the mountain ranges in each of the following groups, describe the general deformation style in terms of compression (thrust and fold belt), volcanic/magmatic, and extension (horst and graben):
   • Group A: US Basin and Range (Nevada/Utah), Sierra Nevada, Tetons
   • Group B: North Cascades, Alps, Himalayas, Appalachians, Urals
   • Group C: Marianas, Indonesia, Aleutians
8. Identify the major events in NW Washington history:
   1. Breakup of Rodinia supercontinent (about 750 Ma).
   2. Accretion of Wrangellia terrane (about 90 Ma) forming most of the metamorphic rocks in the region.
   3. Deposition of sediments (including Chuckanut sandstone) in pull-apart basins (about 50 Ma).
   4. Cascade volcanic arc forms (30 Ma to present) due to subduction.
   5. Columbia River Basalts are extruded (about 15 Ma).
   6. Maximum extent of continental ice sheets (about 18 Ka - 18000 years ago)
   7. Channeled scablands of Eastern WA form from Lake Missoula floods (about 13Ka - 13000 years ago).