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 G-eology. 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, c is the 



