Geology. — “Fractures and Faults near the Surface of Moving 
Geanticlines’. I. By Prof. H. A. Brouwer. (Communicated 
by Prof. G. A. F. MOLENGRAAEFF) 
(Communicated at the meeting of April 23, 1920). 
When erustal movements take place they generally cause strata 
at greater depth to fold, and to break near the surface. In the high 
continental mountain-ranges, as the Alps and the Himalaya, which 
have already very long been exposed to eroding influences, because 
they have already long been lifted above the sealevel, the ancient 
folding phenomenon is completely visible, and the anatomical 
structure has become visible in its broad outlines and in the smallest 
details. Conversely, in the sculpturing of the broad outlines erosion 
has long since obtained a paramount influence by the side of the 
mountain-building movements; whereas the trend of the first valleys 
depended on the first geanticlines that rose above the sealevel, these 
forms have since that epoch long been influenced by the collective 
action of mountain-building and erosion, in which process the 
relationship between the broad outlines of the tectonic and the shape 
of the surface has disappeared more and more. Where, however, 
the mountains rose up from deep seas and were exposed to eroding 
influences during a much shorter space of time, the outer form is 
not controlled in the first place by erosion, but by the crustal 
movements themselves. In contradistinction to the mountain-ranges 
of the continents the erosion of the tertiary mountain-ranges has 
laid bare here chiefly only their superficial parts; here there is no 
question of a “herrliche Entblészung des anatomischen Baues des 
Gebirges”.') But, on the other hand, the now visible external shape 
of the Alpine mountains is only “eine Ruinenbildung’, whereas in 
the recent mountains of the deep seas the main lines of the latest 
phase of mountain-building manifest themselves clearly in the shape 
at the surface, which will be shown in what follows. 
Origin of fractures and faults. 
The origin of fractures and faults is correlated with the occurrence 
of tensional and compressional stress; the developments of fractures 
1) Aue. Heim. Geologie der Schweiz. Band II, Lief. 1, 1919. S: 72: 
