ABSTRACTS OF PAPEES 33 



The process of marine degradation which shapes the continental shelf, and 

 in case of rapid uplift jdelds coast terraces, supplies us with a measure for 

 the rate of crustal deformation. Wherever uplift goes on slowly, as it does 

 about the margins of the Atlantic, the treads of the coast terraces are found 

 to be both broad and elaborately eroded by stream action and the average 

 angle of the terraces is small. Cuestas may be developed. Wherever, on the 

 contrary, uplift is going on rapidly, as it is on the borders of the Pacific area, 

 the treads of coast terraces are narrow and the risers relatively high, the 

 surface of the treads is smooth and but slightly affected by river erosion, and 

 the average angle of the terrace series will be correspondingly large. 



Presented by title at the request of the author. 



OROGENIC FORCES 

 BY HAKRY FIELDING KEID 



(Abstract) 



• Normal faults can not be formed by tension. Vertical forces are necessary, 

 and in general, when the dip is high, horizontal pressure must exist. 



The forces elevating mountain ranges must be distinguished from the hori- 

 zontal forces causing folding. It can be shown that many of our present 

 mountain ranges owe their elevation to vertical forces. 



Read by E. B. Mathews in the absence of the author. 



AN OBJECTION TO THE CONTRACTION HYPOTHESIS AS ACCOUNTING FOR 



MOUNTAINS 



BY FRANK BURSLEY TAYLOR 



{Abstract) 



Under the law of cooling for a molten globe which would cool at a progress- 

 ively diminishing rate, and of contraction which would also follow cooling at 

 a progressively diminishing rate, folding of the earth's crust and mountain- 

 making would go on at a doubly or compounded diminishing rate. The amount 

 of crustal shortening needed to account for the Tertiary mountain belt would 

 require a great accumulation of crustal stresses over a very long time. But 

 the rocks of the crust show clearly by fold-mountains that they are incompe- 

 tent to sustain such accumulations. Huronian tillite in Canada indicates a 

 relatively cold state, like the present, as existing at that early time, so that 

 the amount of cooling in the two or three geological ages preceding the Ter- 

 tiary can not have been as great as in the ages preceding the Huronian. It is 

 to be considered, further, that several mountain-making periods since the 

 Huronian have probably relieved most of the stresses produced in that time, 

 so that the required amount of accumulation for the Tertiary mountain belt 

 was impossible. 



The Tertiary mountain belt shows a world-wide cause which can only be 

 ascribed to an astronomical force. A capture theory for the origin of satellites 

 was proposed some years ago by two or three different authors. A newly cap- 

 Ill — Bull. Geol. Soc. Am., Vol. 32, 1920 



