870 Reviews — Earth Folds and Mountain Formation. 



movements the material of the geanticlines is cooled, and the 

 rocks in them become hard and brittle ; hence when disturbed 

 the uplifted areas are torn by fractures. In the geosynclines, on 

 the contrary, the material is heated and becomes plastic ; hence 

 when disturbed it yields by flowing, and, as the material below 

 the geosyncline is compressed laterally while sinking, the hidden 

 materials are intensely crumpled and altered. Fracturing is especially 

 visible on the margins of the geanticlines, and as the central areas 

 are lowered by denudation the anticlinals are exposed asmetamorphic 

 blocks. Amongst other consequences of this folding of the crust he 

 includes the distribution of exposed metamorphic areas and former 

 climatic changes ; though he does not claim that it has been certainly 

 proved that the glacial climate is due to anticlinal uplift, he believes 

 "that it is the main factor and not improbably the only factor" 

 (pp. 161-2). _ 



In describing the special regions of ' Grossfalte ' he begins with 

 the Malay Archipelago ; he claims that the movements there are 

 independent of the pre-Tertiary structure. The movements began, 

 he says, in the Neogene and were continued more briskly in the 

 Pleistocene ; they produced rift-valleys and sunklands as well as 

 folds and were associated with powerful volcanic eruptions. Among 

 European ' Grossfalten ' he describes the rift-valley of the Ehine, 

 the Pliocene dislocations of the Juras, the Pleistocene uplift of 

 the Alps (proved by Penck for at least 400 metres), the pre- 

 Glacial but young folding of Scandinavia, and the many important 

 recent earth-movements in the Balkans and the ^gean. He favours 

 the tectonic origin of Alpine lake-basins and attributes the long strike 

 valleys of the Alps to tension clefts (Distraktionsrissen). 



In America he describes the St. Lawrence as a recently foundered 

 valley and more striking examples from Western America, where 

 since the Quaternary there have been two great Falten. The 

 eastern began in the Neogene and was enlarged in the Quaternary, 

 while the western happened entirely in the Pleistocene. In Africa 

 the Great Rift Yalley and Madagascar supplies the author's chief 

 examples. He therefore holds that all the continents have been 

 greatly affected geographically by movements of recent age ; although 

 these disturbances are almost Avorldwide in distribution, he 

 recognizes no regularity in their arrangement (p. 160). He attributes 

 to them the determination of the main relief of the lithosphere, both 

 submarine and terrestrial ; and though he remarks that its genesis 

 dates from the pre-Palaeozoic, he holds that the present surface 

 features of the earth are very young in age. Theories of the 

 permanence of oceans and continents he apparently regards as 

 unworthy of discussion. 



Dr. K. Andree, of Marburg, discusses the conditions of mountain 

 formation. He belongs to the same school as Abendanon. His book 

 is divided into three main sections ; the first considers various theories 

 of mountain formation, especially those dealing with the contraction 

 and shrinking of the earth, the tetrahedral theory, the gliding theory 

 of Eeyer, and various thermal or expansion theories. He rejects 

 the theories of the simple contraction and of tangential thrusting. 



