UNIVERSITY OP CALIFORNIA. 



Bulletin of the Department of Geology. 



Vol. 2, No. 6, pp. 155-178. ANDREW C. LAWSON, Editor. 



SOME ASPECTS OF EROSION 



IN 



RELATION TO THE THEORY OF THE PENEPLAIN. * 



BY 



W. S. Tangier Smith. 



CONTENTS. 



Page 



Introduction 155 



Definition of the Term Peneplain 156 



Objections to the Theory of Peneplanation 157 



Absence of Present Peneplains 157 



Difficulty of Fulfilling Necessary Conditions 158 



Limitation of the Term 161 



Use of the Term Beveling 162 



Considerations Modifying Use of Term 163 



Graded Slopes ,....164 



Differential Erosion 166 



Orogenic Movements 171 



" Tilting " 171 



Soil 173 



Vegetation 173 



Conclusion 175 



INTRODUCTION. 



A recent article by Prof. R. S. Tarrf has raised a question as to 

 the validity of the theory of peneplains, and at the same time pro- 

 posed a different explanation for the same phenomena, under the 



* Since this paper was written, an article has been published by Prof. 

 N. S. Shaler (Bulletin of the Geological Society of America, Vol. 10, pp. 

 263-276, " Spacing of Rivers with Reference to Hypothesis of Base-leveling"), 

 in which he reaches conclusions similar to some of those presented here, 

 though by a different line of reasoning. 



t The Peneplain, Am. Geol., Vol. XXI, June, 1898, pp. 351-370. 



