﻿CHAPTER 
  III. 
  

  

  METAMOEPHIO 
  AND 
  ERUPTIVE 
  AREAS. 
  

  

  LA 
  PLATA 
  MOUNTAINS. 
  

  

  In 
  many 
  respects 
  this 
  is 
  a 
  very 
  remarkable 
  group 
  of 
  mountains. 
  Oc- 
  

   cupying 
  an 
  area 
  not 
  more 
  than 
  ten 
  miles 
  square, 
  and 
  being 
  situated 
  in 
  

   the 
  remote 
  southwest, 
  almost 
  isolated 
  from 
  the 
  great 
  mountain-chains, 
  

   it 
  yet 
  has 
  a 
  number 
  of 
  lofty 
  summits 
  which 
  fall 
  but 
  littls 
  short 
  of 
  14,000 
  

   feet 
  elevation. 
  A 
  cluster 
  of 
  these, 
  which 
  lie 
  just 
  north 
  of 
  the 
  head 
  of 
  

   the 
  La 
  Plata 
  River, 
  are 
  among 
  the 
  most 
  rugged 
  and 
  picturesque 
  mount- 
  

   ains 
  in 
  Colorado. 
  The 
  geologic 
  conditions 
  are 
  interesting 
  and 
  peculiar, 
  

   and 
  the 
  mines 
  of 
  silver 
  and 
  gold 
  give 
  promise 
  of 
  very 
  considerable 
  rich- 
  

   ness. 
  

  

  The 
  La 
  Plata 
  River 
  heads 
  a 
  little 
  north 
  of 
  the 
  center 
  of 
  the 
  group, 
  

   and 
  occupies 
  a 
  great 
  caiioned 
  valley, 
  which 
  opens 
  out 
  to 
  the 
  south. 
  On 
  

   either 
  side 
  of 
  this 
  valley 
  are 
  two 
  great 
  wiugs 
  or 
  spurs, 
  on 
  which 
  tbere 
  

   are 
  several 
  high 
  points. 
  These 
  spurs 
  come 
  togetlier 
  around 
  the 
  head 
  

   of 
  the 
  valley 
  and 
  connect 
  with 
  the 
  spire-like 
  summits 
  of 
  the 
  central 
  

   mass. 
  Extending 
  northwest 
  from 
  the 
  principal 
  cluster 
  of 
  summits, 
  be- 
  

   tween 
  the 
  two 
  branches 
  of 
  the 
  West 
  Maucos, 
  is 
  a 
  short, 
  narrow, 
  crested 
  

   ridge, 
  which 
  terminates 
  in 
  the 
  highest 
  summit 
  of 
  the 
  entire 
  group. 
  To 
  

   this 
  we 
  have 
  given 
  the 
  name 
  Hesperus, 
  on 
  account 
  of 
  its 
  being 
  located 
  

   farther 
  west 
  than 
  any 
  other 
  high 
  mountain 
  in 
  Colorado. 
  

  

  Of 
  the 
  central 
  summits 
  there 
  are 
  two 
  sections 
  — 
  one 
  that 
  is 
  in 
  plain 
  

   view 
  from 
  the 
  valley 
  of 
  the 
  La 
  Plata 
  below, 
  and 
  another 
  a 
  mile 
  or 
  more 
  

   farther 
  north. 
  The 
  latter 
  has 
  two 
  fine 
  crests 
  5 
  the 
  one 
  nearest 
  Mount 
  

   Hesperus 
  seems 
  quite 
  inaccessible, 
  and 
  looks 
  from 
  the 
  w^st 
  like 
  a 
  

   great 
  bundle 
  of 
  needles 
  or 
  splinters, 
  so 
  deeply 
  scarred 
  are 
  its 
  vertical 
  

   sides 
  and 
  so 
  sharp 
  its 
  thousand 
  spires. 
  I 
  have 
  named 
  it 
  Mount 
  Moss, 
  

   after 
  the 
  indomitable 
  Capt. 
  John 
  Moss, 
  of 
  Parrott 
  City. 
  

  

  From 
  this 
  peak 
  one 
  great 
  spur 
  extends 
  to 
  the 
  north 
  between 
  the 
  West 
  

   Mancos 
  and 
  the 
  south 
  branch 
  of 
  Bear 
  River, 
  aiid 
  another 
  to 
  the 
  east, 
  

   between 
  the 
  La 
  Plata 
  and 
  South 
  Bear. 
  The 
  latter 
  ridge 
  divides, 
  and 
  

   sends 
  out 
  one 
  branch 
  between 
  the 
  Bear 
  and 
  Animas, 
  another 
  extends 
  

   to 
  the 
  east 
  between 
  Hermoso 
  and 
  Junction 
  Creeks, 
  and 
  the 
  third 
  and 
  

   main 
  spur 
  extends 
  south, 
  and 
  forms 
  the 
  east 
  wing, 
  the 
  La 
  Plata 
  Mount- 
  

   ains. 
  

  

  In 
  making 
  out 
  the 
  general 
  geologic 
  features 
  of 
  Colorado, 
  as 
  illus- 
  

   trated 
  in 
  Plate 
  XXXI 
  V, 
  I 
  included 
  the 
  La 
  Plata 
  Mountains 
  in 
  the 
  meta- 
  

   morphic 
  belt, 
  because 
  the 
  central 
  portion 
  of 
  the 
  group, 
  as 
  exposed 
  by 
  

   the 
  deep-cut 
  valley 
  of 
  the 
  La 
  Plata 
  River, 
  is 
  highly 
  metamorphic, 
  and 
  

   is 
  composed 
  principally 
  of 
  uplifted 
  and 
  altered 
  sedimentary 
  rocks. 
  But 
  

   there 
  are 
  associated 
  with 
  these 
  to 
  a 
  very 
  considerable 
  extent 
  eruptive 
  

   rocks, 
  and 
  very 
  great 
  complication 
  of 
  structure 
  is 
  the 
  result. 
  In 
  con- 
  

   sidering 
  the 
  metamorphic 
  character 
  of 
  this 
  group, 
  I 
  find 
  that 
  it 
  is 
  asso- 
  

   ciated 
  with 
  the 
  great 
  metamorphic 
  group, 
  which 
  lies 
  to 
  the 
  northeast 
  

   about 
  the 
  Animas, 
  and 
  seems 
  to 
  be 
  a 
  prolonged 
  spur 
  or 
  offshoot 
  of 
  that 
  

   2G8 
  

  

  