Domes and Dome Structure. 211 



DOMES AND DOME STRUCTURE OF THE HIGH 

 SIERRA. 



By G. K. Gilbert. 



[Reprinted with permission from Bulletin of the Geological Society of. 

 America, February lo, 1904 ] 



General Character of the Domes. — In the granite areas 

 of the Sierra Nevada are many hills and other summits 

 having the form of domes. A few of the domes are sym- 

 metric, with approximately circular or oval bases, but the 

 majority are somewhat one-sided or irregular. Associated 

 with these domelike forms are closely related structures. 

 The granite is divided into curved plates or sheets which 

 wrap around the topographic forms. The removal of one 

 discloses another, and the domes seem at the surface to be 

 composed, like an onion, of enwrapping layers. 



Theories of Relation between Structure and Form. — 

 In explanation of these peculiar forms and structures two 

 general theories have been advanced.* According to one 

 theory, the separation of the granite into curved plates is 

 an original structure, antedating the sculpture of the 

 country and determining the peculiarities of form. Ac- 

 cording to the other theory, the structure originated sub- 

 sequently to the form, and was caused by some reaction 

 from the surface. Visiting the Sierra in the summer of 

 1903, I had these two theories in mind, and sought for 

 characters by which they might be tested. 



* H. W. Turner gives a digest of opinions, with references, in Proc. 

 Cal. Acad. Sci., 3d ser., Geology, vol. i, pp. 312-315. To his eumeration may 

 be added Muir (Am. Assoc. Adv. Sci. Proc, vol. 23, pp. 61-62) and 

 Le Conte (Elements of Geology, 4th ed., pp. 283-284), both on the side of 

 original structure. 



