CONTORTED STRATA. 



Contorted ftra 



upon its face, nor any transported materials be accumulated parallel to 

 it. An originally perpendicular layer or deposit of earthy materials 

 is obviously impossible. Whenever, therefore, we behold vertical 

 strata, we may be quite sure that they were not deposited in that 

 form, but have been displaced by some internal movements of the 

 earth. 



Vertical Strata. Abundance of instances of this position of 

 strata may be quoted in almost any part of the world. The Isle of 

 Wight gives us, in Alum Bay and Whitecliff Bay, a magnificent series 

 of strata, ITOO feet in thickness, reared into an absolutely vertical 

 position ; and this effect is the more remarkable, because the materials 

 uplifted consist of many strata of loose sands and pebbles, which 

 most certainly have been deposited nearly leveL Similar phenomena 

 are seen in the Isle of Purbeck. In the western borders of York- 

 shire, vertical strata of limestone range for miles parallel to the edge 

 of the Pennine chain, and turn eastward through Craven, below Ingle- 

 borough and Pennyghent, to Settle. Magnificent examples of vertical 

 strata are familiar to those who have visited the mountains of Savoy, 

 or who have read the graphic descriptions of Saussure. 



Contorted Strata. There are some remarkable instances of con- 

 torted stratification very difficult to be explained without supposing 

 the strata to have been soft at the time of the flexure. Not to dwell 



on inferior examples, we shall 

 quote the magnificent phenomena 

 of this kind which are seen in 

 the valleys of Chamouni and Lau- 

 terbrunnen, along the shores of 

 the Lake of Lucerne near Fluellen, 

 and the schistoze rocks of the 

 stack in Anglesea. The stratified 

 limestones and other rocks of these 

 localities are bent with such extra- 

 ordinary retroflexions, as to imply 

 repeated or continuous operations 

 of the most violent mechanical 

 agency, producing displacements in different directions ; and observa- 

 tions along the range of the Alps prove that the whole of this chain 

 has been the theatre of enormous and reiterated convulsions, such 

 as might be anticipated from the amount of compression which must 

 have been necessary to uplift that mountain chain. 



Faults. But the most singular case of disturbance is when strata, 

 either horizontal or inclined, being too rigid to bend under flexure, 

 break, and are displaced, so that on one side of the line of fracture the 

 corresponding rocks are much higher than on the other. This differ- 

 ence of level in places sometimes amounts to hundreds or even thou- 

 sands of yards. The succession of strata is on each side the same, 

 their thickness and qualities are the same, and it seems impossible to 

 doubt that they were once connected in continuous planes, and have 

 been forcibly and violently broken asunder. 



Fig. 28. 



