STRATIFICATION. 



103 



this cause are necessarily of limited extent, since the conditions 

 required for the result are not such as are likely to exist on a very 

 large scale. 



It follows, from these facts, that, unless strata have been disturbed 

 from their natural positions, the order in which they lie is the order of 

 relative age, — the most recent being highest in the series. 



111. (2.) Dislocations of strata. — Strata, although generally in 

 horizontal positions when formed, are in most regions, at the present 

 time, tilted, or inclined, and the inclinations vary from a small angle 

 to verticality, or even beyond verticality. They have been raised 

 into folds, each fold often many miles in sweep and equal to a 

 mountain-ridge in extent. They have been crumpled up into 

 groups of irregular flexures, one fold or flexure succeeding to 

 another, till like a series of wrinkles — and necessarily coarse 

 wrinkles — on the earth's surface. Every mountain-region presents 

 examples of these flexures, or uplifts ; and most intermediate plains 

 have at least some undulations in conformity with the system in the 

 mountains. 



In connection with all this uplifting, there have been frac- 

 tures on a grand scale ; and strata thus broken have been dis- 

 placed or dislocated by a sliding of one side of such a fracture 

 on the other, through varying distances from a few feet to 

 miles, — one side dropped down to this extent, or the other side 

 shoved up. 



The subject, then, of the dislocations of strata is an important 

 one in Geology. The history of the continents and their mountain- 

 ranges, as well as of all their strata, is involved in it. 



112. Uplifts, Folds, Dislocations. — The following sections illus- 

 trate the general facts respecting these uplifts, folds, and dis- 

 locations. 



Fig. 96. 



Fig. 97. 



Fig. 96 represents a part of the Coal formation broken and dislo- 

 cated, the beds (the coal-beds 1 and 2 and the other layers) being 

 changed in direction as well as disjoined in the fracturing. Fig. 97 

 is another example of similar kind and greater extent, e is the 



