HYPOGEiC WORK. 389 



6. Ranges, Systems, Chains, Cordilleras in North America. — From the 

 explanations given it is apparent that a mountain range includes all the 

 mountain ridges made over the area and border of a single geanticline. The 

 Appalachian is an example 900 miles long; it comprises many ridges, but 

 these are made by denudation. Ranges are the individuals or units in 

 mountain structures. 



A mountain system includes all ranges in a region made in different, more 

 or less independent, geosynclines at the same epoch. Besides the birth of 

 the Appalachian Eange at the close of the Carbonic era, there was also 

 the birth of an Acadian Range, from Newfoundland through Nova Scotia, 

 and probably to Rhode Island. Here are two simultaneously made ranges 

 on the Atlantic border, and they may be regarded as parts of an Appalachian 

 mountain system. Again, in western Arkansas, the upturned Paleozoic 

 rocks constitute the Ouachita Mountain range, which, as L. S. Griswold has 

 suggested, pertains to the Appalachian Mountain system, the axis of uplift 

 conforming to the southern portion of the latter in Tennessee and Missis- 

 sippi. As another example, the Wasatch Mountains constitute one of the 

 Laramide ranges. But the mountains to the north of Montana, in British 

 America, described on pages 359-60, were evidently made over another trough 

 in the same line, and correspond to another Laramide range. So there are 

 others, and as many as there were independent or partially independent 

 Lar?mide troughs along this line in the Rocky Mountains ; and all the 

 mountain ranges originating from these troughs make up the Laramide 

 Mountain system of North America, over 4000 miles long. 



A moimtain chain is a combination of mountain systems, or mountain 

 belts of different epochs. On the Atlantic side, there is, along the Appalachian 

 belt, a combination consisting of the Appalachian system of post-Carbonifer- 

 ous age, the Taconic system of Middle Silurian age, and an Archaean system; 

 and the Palisade mountain system, of Jurassic age, may be added. Together 

 they constitute the Appalachian Chain. 



In the Rocky Mountains, the main Rocky Mountain Chain of British 

 America, which, as has been stated, is continued southward along the 

 Wasatch Range, includes an Archaean system and the Laramide or post- 

 Cretaceous system. The chain is not continued in sight, south of the 

 Wasatch ; but the line is an important geological boundary, it being the 

 western limit of the Cretaceous formation, and the eastern of the Great 

 Basin. The Front Range of Colorado, as it is called, is the course of another 

 Archaean system and also of other Laramide uplifts, and, therefore, of another 

 summit chain, — which may be called the Colorado Chain. 



Again, nearer the coast, the mountain belt which includes the Sierra 

 Nevada of California, the Cascade Range of Oregon and Washington, the 

 long Coast Range of British Columbia, as it is called by G. M. Dawson, 

 together with the range to the south, 1000 to nearly 5000 feet high, along 

 the California peninsula, are parts of a Sierra chain, combining ranges or 

 systems of ranges, of Archaean and later time. In like manner there is a 



