﻿10S 
  C. 
  Keyes 
  — 
  A 
  Rotating 
  Straticulate 
  Spheroid. 
  

  

  Art. 
  VI. 
  — 
  Tectonic 
  Adjustment 
  of 
  a 
  Rotating 
  Straticu- 
  

   late 
  Spheroid; 
  by 
  Charles 
  Keyes. 
  

  

  Notwithstanding 
  the 
  fact 
  that 
  with 
  reference 
  to 
  strains 
  

   of 
  deformation 
  the 
  behavior 
  of 
  the 
  earth 
  as 
  a 
  whole 
  is 
  

   that 
  of 
  a 
  body 
  having 
  the 
  rigidity 
  of 
  steel, 
  the 
  transloca- 
  

   tion 
  of 
  matter 
  within 
  is 
  mainly 
  analogous 
  to 
  that 
  taking 
  

   place 
  in 
  a 
  highly 
  viscous 
  liquid. 
  With 
  the 
  exception 
  of 
  

   the 
  thin 
  outer 
  crust 
  all 
  internal 
  change 
  of 
  mass 
  position 
  

   is 
  necessarily 
  by 
  normal 
  flow 
  movement. 
  Only 
  in 
  this 
  

   exterior 
  film 
  where 
  the 
  load 
  pressure 
  is 
  less 
  than 
  that 
  of 
  

   the 
  crushing 
  strength 
  of 
  rock 
  and 
  where 
  rocks 
  of 
  differ- 
  

   ent 
  strengths 
  alternate, 
  do 
  folding 
  without 
  rupture 
  and 
  

   faulting 
  without 
  flexing 
  take 
  place. 
  It 
  is 
  the 
  finely 
  stra- 
  

   ticulate 
  character 
  of 
  this 
  surface 
  zone 
  that 
  enables 
  def 
  or- 
  

   mative 
  effects 
  to 
  be 
  quantitatively 
  measured. 
  To 
  this 
  

   layered 
  cuticle 
  are 
  of 
  course 
  the 
  chief 
  investigations 
  of 
  

   the 
  geologist 
  confined. 
  

  

  Geologically 
  the 
  zone 
  of 
  rock-flowage 
  does 
  not 
  really 
  

   begin 
  at 
  a 
  definite 
  theoretical 
  depth 
  as 
  usually 
  postu- 
  

   lated 
  — 
  at 
  the 
  distance 
  from 
  the 
  surface 
  where 
  the 
  strong- 
  

   est 
  rocks 
  commence 
  to 
  be 
  crushed, 
  or 
  at 
  a 
  level 
  of 
  5 
  or 
  6 
  

   kilometers 
  down. 
  The 
  controlling 
  factor 
  of 
  rock-flow 
  is 
  

   not 
  so 
  much 
  any 
  absolute 
  load 
  of 
  superincumbent 
  mate- 
  

   rial 
  as 
  it 
  is 
  the 
  lithological 
  or 
  textural 
  nature 
  of 
  a 
  given 
  

   rock 
  prism. 
  Although 
  the 
  crushing 
  strength 
  of 
  the 
  

   toughest 
  granite 
  is 
  a 
  column 
  10 
  kilometers 
  or 
  so 
  in 
  height, 
  

   perfect 
  slipping 
  of 
  component 
  particles 
  over 
  one 
  another, 
  

   which 
  is 
  in 
  all 
  essential 
  respects 
  true 
  rock-flow, 
  occurs 
  in 
  

   such 
  formations 
  as 
  shales 
  within 
  a 
  few 
  hundreds 
  of 
  

   meters 
  of 
  the 
  earth's 
  surface. 
  For 
  this 
  reason 
  it 
  is 
  that 
  

   thick 
  sections 
  in 
  which 
  the 
  rocks 
  are 
  chiefly 
  argillaceous, 
  

   as 
  in 
  the 
  Appalachian 
  region 
  for 
  instance, 
  give 
  rise 
  to 
  a 
  

   characteristic 
  type 
  of 
  orographic 
  structure 
  which 
  is 
  

   dominantly 
  flexing. 
  When 
  the 
  rock 
  column 
  is 
  princi- 
  

   pally 
  composed 
  of 
  hard 
  and 
  brittle 
  materials 
  tectonic 
  

   adjustment 
  is 
  an 
  entirely 
  distinct 
  kind 
  of 
  orogeny. 
  

   There 
  is 
  marked 
  rupture 
  or 
  faulting 
  of 
  the 
  layers. 
  The 
  

   mountain 
  ranges 
  of 
  the 
  Great 
  Basin 
  and 
  the 
  Mexican 
  

   tableland 
  well 
  illustrate 
  such 
  phases. 
  In 
  a 
  somewhat 
  

   different 
  way 
  and 
  without 
  attempt 
  at 
  any 
  explanation 
  of 
  

   the 
  fact 
  this 
  great 
  generalization 
  was 
  put 
  forth 
  many 
  

   years 
  ago 
  by 
  the 
  late 
  Major 
  J. 
  W. 
  Powell 
  of 
  Washington. 
  

  

  