BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 22, pp. 123-176, PLS. 7-13 MAY 10, 1911 



EEPEATING PATTEKNS m THE EELIEF AND IN THE 

 STEUCTURE OF THE LAND^ 



BY WILLIAM HERBERT HOBBS 



{Presented extemporaneously before the Society December 27, 1910) 



CONTENTS 



Page 



Relief patterns in landscapes 124 



Character profiles 124 



Space units in profiles 127 



Different orders of space units 128 



Relief patterns in topographic maps 129 



Checkerboard topography 129 



The primary unit of the subdivision 131 



Drainage networks 133 



Normal network in rocks devoid of structure planes 133 



Structural control of networks 134 



Merging of network patterns 140 



Patterns obscured by bedplanes and formation boundaries 141 



Obscure patterns revealed in studies of the joint system 143 



The dividing lines of relief patterns — lineaments 143 



The varied expression of lineaments 143 



Relation to joints and faults 144 



Identity of many strong lineaments with seismotectonic lines 146 



Character of seismotectonic lines 146 



The meshlike arrangement of volcanic vents 148 



The correlation of fracture fields 148 



Controlled fracture fields of North America 148 



Disorderly fracture fields 155 



European fracture fields which exhibit control ; . . 158 



The African fracture system .• 162 



The primary fracture pattern of the earth's shell 163 



Deductions concerning the nature of faults 165 



Difficulties in the way of securing fault maps 165 



The inherited conception of a fault 166 



Joints and faults comprised in one system 166 



Example of a fault system 168 



A fracture system model 171 



1 Manuscript received by the Secretary of the Society December 29, 1910. 



X — Bull. Geol. Soc. Am., Vol. 22, 1910 (123) 



