Environmental Engineering Reference
In-Depth Information
Figure 25.1
The form and origin of the Andes. (a) Principal
Andean cordillera, etc.; SA Sub-Andes, EC Eastern
Cordillera, A Altiplano, CC Central Cordillera, WC Western
Cordillera, CTC Coastal Cordillera. (b) Granite batholiths.
(c) Formation of the Peruvian-Bolivian sector from island
arc to arc-continent collision.
Source: Partly after James (1973).
tectonics elevate the Aleutian and Alaska ranges and coastal mountains of Alaska and
British Columbia, up to 250 km wide. The highest coastal cordillera reach 4·0-6·2 km
and include Mount Denali (6194 m), the highest peak in North America. Lower
cordilleran systems lie inland, separated by narrow coast-parallel intermontane basins.
Farther south, coastal ranges from Washington to southern California rarely reach 3 km
high, but the more extensive Cascade and Sierra Nevada ranges rise 3·5-4·4 km east of
the Willamette and Sacramento-San Joaquin basins (see Colour Plate 14 between pp. 272
and 273). The former includes the ice-capped stratovolcanoes of Mount St Helens, Mount
Hood, Mount Rainier, etc., with the highest peak in the contiguous states, Mount Whitney
(4418 m), in the latter.
American cordillera are high enough to support mountain icefields intermittently
throughout their length, including equatorial Ecuador, where the snowline rises to 4·6 km.
