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SELF QUIZ 17: GEOLOGY OF THE SOUTHWEST
Questions | Answers
 

1. Alluvial fan: the material eroded out of a canyon that gets dumped in a fan-shape at the end of the canyon.
Bajada: the conglomeration of alluvial fans that forms a slope from the sides of mountains.
Playa: the area at the bottom of valleys that fills with water after hard rains.

2. Igneous: from melted rock that has solidified.
Metamorphic: from another rock that has been changed under heat and pressure.
Sedimentary: from sediment that has been solidified

3. Intrusive Igneous: melted rock cools underground.
Extrusive Igneous: melted rock cools above ground.

4. Sierras: Farallon Plate subducts under North American Plate producing volcanic mountain chain.
Rockies: Farallon Plate subducts under North American Plate at low angle and "sticks", causing compression, and scrapes up from the bottom of the North American Plate, which creates the Rockies by thrusting and folding.
Basin and Range: After the last of the Farallon Plate subducts beneath the North American Plate, crustal extension occurs, producing a series of normal faults throughout the southwest, causing down-dropped valleys (basins) and uptilted mountains (ranges).
Colorado Plateau: uplifted block; don't know why.

5. Large volcano collapses and forms Caldera. Crustal extension causes Detachment Fault that moves Tucson Mt. Caldera 20 miles to the southwest (to approximately where Tucson Mountains are today). Further crustal extension (the Basin and Range Disturbance) produces a series of normal faults, dropping down Tucson Valley and lifting up Tucson and Catalina Mountains. Erosion has resulted in current form of Tucson Mts., Tucson Basin, and Santa Catalinas.