62 



GEOMORPHOLOGY: 



FOLDS 



symmetrical 



asymmetrical 



inclined 



isoclinal 



Figure 4.23 Diostrophism: attitude, warping and folding of strata. 



In both domes and basins, many square miles of 

 landscape are involved. 



Folding. Widespread surface compressing and 

 some settling movements may form a washboard- 

 like topography of more or less symmetrical folds. 

 The elevations so formed are called anticlines and the 

 depressions, syndines. However, some folding creates 

 less symmetrical land forms. Some of these less sym- 

 metrical forms are illustrated and named in Figure 

 4.23. If folds are somewhat tilted from the vertical, 

 inclined or overturned folds results. If folds are 



pushed together, the product is an isoclinal fold. 

 When folds are tilted over so far that their peaks 

 almost point to the horizon, the land form is called 

 a recumbent fold (or folds). If additional pressure 

 is applied to recumbent folds, they may break and 

 have part thrust toward and over the rest, creating 

 complicated mountain structures called nappes. In 

 addition to producing folds, folding may raise the 

 rock layers on one side of a line and lower them on 

 other side, creating a monocline. 



Folding produces various other types of land forms. 



