DISLOCATIONS OF STRATA. 



105 



rocks of Canada. The folded rocks are often overlaid by others of 

 more recent date. 



113. In describing the positions of strata, the following terms 

 are used : — 



a. Outcrop. — A ledge or mass of rock coming to the surface, or 

 cropping out to view at the surface or above it (fig. 101). 



Fig. 101. 



b. Dip. — The slope of the strata, or the angle which the layers 

 make with the plane of the horizon; as a p (fig. 101). The direction 

 of the dip is the point of the compass towards which the strata 

 slope : for example, the dip may be 25° to the southeast, or 15° to the 

 west, and so on. 



c. /Strike. — The direction at right angles with the dip, or the 

 course of a horizontal line on the surface of the inclined beds, 

 as s t. 



The outcropping edges are sometimes called basset edges. 



d. Anticlinal. — An anticlinal ridge is a ridge made of strata sloping 

 in opposite directions, as a, b, c, in fig. 99. An anticlinal axis is 

 the axial or ridge line of such a ridge : it lies in the axial plane a x. 

 The word anticlinal is from the Greek avn, opposite, and kXivu, I 

 incline. 



e. Synclinal. — A synclinal valley is a valley formed by strata sloping 

 downward from either side, as the middle part of fig. 99 b ; and a 



