XXviii GEOLOGY OF THE HIGH PLATEAUS. 



CHAPTER Y. 

 Spectoations concbrning the causes of volcanic action ^ 1 J3 



The probable locus of volcanic activity.-Volcauism inconsistent with the notion of an all-Uqnid 

 inferior—Localization of t he phenoniona.-Indei.eudence of vents.-Comparison of lavas with 

 metamorphic rocks.-Synthetic character of basalt.-Dynamical causes of eruptions. -Local 

 increments of subterranean teniperature.-Mechanics of eruption—Application of hydrostatic 

 pnnc.ples-Explanation of the sequence of eruptions— A compound function of tempera- 

 ture, density, and fusibility— Discussion of the hypothesis— Exceptions and anomaUes -The 

 ultimate cause unknown. 11.1-142. 



CHAPTER VI. 



Sedimkntaky formations of the District of the High Plateaus 



The Paleozote— The Shin^mp or Lower Trias.-The Vermilion Cliflfe or Upper Trias—The Ju- 

 rassic— The Cretaceous.-The Eocene. 143-159. iueju 



. CHAPTER VII. 

 The Wasatch Plateau 



143 



CHAPTER VIII, 

 The Tushak 



Sevior Va ley from Gnamson southward-General structure of the northern part of the range- 

 Its intermediate character between the basin and plateau types-Rugged character of the 

 northern portion.-Bulhon Canon.-Rhyolitic eruptions.-Southern portion of the Tushar.- 



nose «T,Vrf "rt"-T"''*"'-' "' ''"' '''"S«-Alternations of volcanic activity and re- 

 pose.— The Tushar fault.— Succession of eruptions. 169-187. 



CHAPTER IX. 

 The MabkXgunt Plateau 



General description.-Dog Valley and its eruptive masses.-Bear Valley. -Little Creek Peak - 



Laltfieldr^P -ft'-rf^'f '"''""'' "'''"' ^l-'-k^g-^^t-Succession of eruptions- 

 Basalt field8.-Panquitch Lake and recent basaltic outpours.-Sedimentaryformations.-Out- 

 look from the southern verge of the plateau. 188-210. "•"nous, uui- 



CHAPTER X. 



Sevier Valley and its alluvial conglomerates 



Upper Sevier or Panquitch Valley.-Panquitch Canon.-Circle Valley.-Origin of Circle Val- 

 ley.--Modes of accumulati<m of conglomeratcs.-Alluvial cones.-Identity ff origin of he old 

 conglomerates and the aUuvia now accumulating in the valleys. 211-224 



160 



Its structure-Strata composing its mass.-Tho great monoclinal— Gunnison Valley.-Salina 



olL7' Bitter r™TT'^'''''''-7^r '''''n Pl'^t—S-li-ontary beds of the Wasatch Mono- 

 oline.— Bitter Creek, Lower and Upper Green River beds. 160-168. 



169 



188 



211 



