402 



SIR A. GEIKIE ON THE TERTIARY 



[May 1896, 



basalts, probably point to much more vigorous displacement within 

 the terrestrial crust. 



Fig. 31. — Reversed fault on the 

 eastern side of Svino, Faroe 

 Isles. 



— LULU JlTDTfi 



T 'MH ) Mll^r^- 



il^llli^l^lll'llflkW 



t )\ ; ~ } } S_i} n H lul"'' li! '' iM . 



4PU^rrrniii/i 



TT 



Fig. 32. — Reversed fault on the 

 N.E. headland ofSando, Faroe 

 Isles. 



On tbe eastern side of Svino 

 a fault with a low hade runs 

 from sea-level up to the top of 

 the cliff, a height of several 

 hundred feet. It has a down- 

 throw of a few yards, but is a 

 reversed fault, as will be seen 

 from fig. 31. Another similar 

 instance may be noticed on 

 the north-eastern headland of 

 Sando, where, however, on the 

 upcast side, the basalts appear 

 as if they had been driven up- 

 ward, a portion of them having 

 been pushed up into a low arch 

 (fig. 32). 



When the Tertiary basalt- 

 plateaux come to be worked out 

 in detail, many examples of 

 dislocation will doubtless be 

 discovered. We shall then 

 learn more of the amount and 

 effects of the terrestrial dis- 

 turbances which have affected 

 North-western Europe since 

 older Tertiary time. In the 

 meantime evidence enough has 

 been adduced to prepare us for 

 proofs of very considerable re- 

 cent displacements even among 

 regions of crystalline schists 



like that which has been disrupted by the Morven fault above 

 alluded to. While the study of the Tertiary volcanic rocks demon- 

 strates the vast general denudation of the country since older 

 Tertiary time, the proofs that these rocks have been faulted acquire 

 a special interest in relation to the origin and evolution of the 

 topography of the region. 



X. The Effects of Denudation. 



Among the more impressive lessons which the basalt-plateaux of 

 North-western Europe teach the geologist, the enormous erosion of 

 the surface of this part of the continental area since older Tertiary 

 time takes a foremost place. He may be ready almost without 

 question to accept the evidence adduced in favour of a vast amount 

 of denudation among such soft and incoherent strata as those of 

 the older Tertiary formations of the South-east of England. But 

 he is hardly prepared for the proofs which meet him among the 

 north-western isles that such thick masses of solid volcanic rocks 

 have been removed during the same geological interval.- - 



