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Mountains by folding are generally of moderate elevation, while mountains by fracture include the highest chains of the globe. The Appalachian Mountains in North America, and the Jura in Europe, are examples of the first; the Rocky Mountains, Andes, Alps and Himalayas, of the second.

Folded mountains are curved into long arches, either entire or broken at the summit and forming a system of long, parallel ridges, of nearly equal height, separated by trough-like valleys. Here and there, however, deep gaps, or gorges, cut the chains allowing the rivers to escape from one valley to another.

In systems of mountains produced by fracture, there is usually one main central chain, with several subordinate ranges. They have, however, less regularity and similarity among themselves than the parallel chains of mountains by folding.

The crests are deeply indented, cut down one-third or one-half the height of the range, forming isolated peaks and passes which present to the eye the appearance of a saw, called in Spanish Sierra; in Portuguese, Serra. Such ranges are frequently distinguished by these terms, as the Sierra Nevada, in North America; and the Serra do Mar, in Brazil.