THE earth's contour AND SURFACE SUBDIVISIONS. 25 



border, lying between the Wasatch line and the line of the Front Kange, is 

 distinctively a Rocky Summit area, and peculiar to the United States portion 

 of the chain. A cordillera is a combination of mountain chains. 



The Coast Cordillera Avithin about 150 miles of the coast includes the 

 Sierra Nevada and Cascade ranges and a range in continuation in British 

 Columbia, which constitute together a Sierra Chain, and have heights equal 

 to those of the Rocky Mountain summit, and a Coast Chain 2000 to 4000 

 feet high in California, which is continued in the Vancouver Range of British 

 America, — 484 feet high in one Vancouver peak, — and, beyond the islands 

 of the coast, in the lofty Fairweather and St. Elias line of heights. On the 

 terms range, system, chain, cordillera, etc., see further, page 389. 



Plateaus. — A plateau is an extensive elevated region of flat or hilly 

 surface, sometimes intersected by ranges of mountains. Any extensive range 

 of generally flat country that is over a thousand feet in altitude is called a 

 plateau. It may lie along the course of a mountain chain, or occupy a wide 

 region between distant chains. The high land that forms the southern half 

 of ]Srew York is generally 1500 to 2000 feet high, and reaching an elevation of 

 more than 4000 feet in the Catskills, is the northern part of a plateau which 

 southward exteuds through Pennsylvania to Tennessee, and in the latter re- 

 gion constitutes the Cumberland Table-land. It is an example of a marginal 

 plateau, connected in origin with a mountain range, — that of the Appalachian 

 Mountains, — and constituting its outer margin. The channeling action of 

 running water has mostly obliterated the plateau character, and converted the 

 region into a group of peaks, ridges, and valleys. In this way high plateaus 

 have often been sculptured into mountain-like forms. The " high plateaus " 

 of southern Utah, which range in height from 7000 to 9500 feet, are properly 

 a marginal appendage to the Wasatch Range, as their elevation was connected 

 with that attending the making of these mountains. 



Other plateaus are intermont plateaus. They occupy the interval between 

 mountain ranges, chains, or cordilleras, and are the highest and largest of 

 plateaus. Between the Rocky and Sierra cordilleras a broad plateau 

 extends from Mexico northwestward through British America. It is mostly 

 from 3000 to 5000 feet in altitude, but the Columbia River and the Colorado 

 have each cut a way through the Sierra Chain and reduced the level by 

 denudation. There are many high ridges in the plateau, parallel in course, 

 or nearly so, to the mountain ranges of the sides, and in part of Oregon and 

 of British Columbia ridges occupy the whole breadth; but in general the 

 plateau features are well defined. 



The portion of the plateau between the Colorado and Columbia rivers 

 is called the Great Basin. It has the Great Salt Lake and the Wasatch 

 Mountains on the east, and the Sierra Nevada and Cascade Mountains on 

 the west, and in this part it is nearly 500 miles wide. Its surface is mostly 

 4000 to 5000 feet above tide level ; but although so high, it has no outside 

 drainage. Its streams are short, and dry up over arid saline plains or end in 

 saline lakes. Great Salt Lake, in Utah, is one of these lakes near its eastern 



