﻿220 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  and 
  J 
  to 
  1 
  inch 
  deep. 
  The 
  material 
  showing 
  them 
  is 
  a 
  light-brown 
  tra- 
  

   chyte, 
  belonging 
  to 
  Ko. 
  3, 
  upper. 
  Its 
  compact 
  feldspathic 
  paste 
  and 
  the 
  

   diminutive 
  crystals 
  of 
  segregated 
  minerals 
  have 
  tended 
  to 
  preserve 
  as 
  

   completely 
  as 
  possible 
  the 
  finest 
  lines 
  and 
  the 
  mirror-like 
  polish 
  that 
  the 
  

   repeated 
  jDassage 
  of 
  ice 
  over 
  its 
  surface 
  has 
  produced. 
  Though 
  through 
  

   unimportant 
  local 
  displacements 
  the 
  direction 
  of 
  the 
  striation 
  on 
  many, 
  

   even 
  large 
  portions 
  of 
  rocks, 
  has 
  been 
  changed 
  from 
  its 
  original 
  posi- 
  

   tion, 
  the 
  main 
  direction 
  is 
  toward 
  the 
  deep 
  valley 
  of 
  the 
  Chama. 
  As 
  we 
  

   proceed 
  farther 
  north, 
  however, 
  riding 
  over 
  the 
  bare 
  rocks 
  that 
  are 
  

   striated 
  and 
  grooved, 
  a 
  change 
  takes 
  place, 
  and 
  we 
  find 
  that 
  instead 
  of 
  

   their 
  main, 
  direction 
  being 
  toward 
  the 
  south, 
  it 
  was 
  now 
  toward 
  the 
  

   east, 
  in 
  a 
  line 
  with 
  the 
  headwater 
  drainage 
  of 
  Eio 
  Conejos. 
  Hun- 
  

   dreds 
  of 
  little 
  ponds 
  have 
  formed 
  in 
  the 
  shallow 
  depressions 
  produced 
  

   by 
  the 
  slight 
  excavating 
  action, 
  of 
  the 
  ice 
  and 
  its 
  accompanying 
  

   bowlders 
  and 
  detritus. 
  More 
  than 
  25 
  square 
  miles 
  must 
  have 
  been 
  

   covered 
  on 
  the 
  plateau 
  by 
  this 
  extensive 
  glacier, 
  although 
  there 
  were 
  

   some 
  points 
  there 
  that 
  could 
  not 
  be 
  reached 
  by 
  the 
  ice. 
  The 
  plateau 
  

   slopes 
  toward 
  the 
  east 
  about 
  at 
  the 
  center 
  of 
  the 
  ancient 
  glacier, 
  and 
  in 
  

   that 
  direction 
  the 
  ice 
  moved. 
  Bowlders 
  are 
  found 
  lying 
  around 
  but 
  not 
  

   in 
  any 
  regular 
  order, 
  for 
  obvious 
  reasons. 
  As 
  soon 
  as 
  the 
  moving 
  agent 
  

   of 
  erosion 
  separated 
  into 
  several 
  arms 
  and 
  reached 
  the 
  easily 
  crumbling 
  

   tra-chytic 
  conglomerate, 
  it 
  turned 
  its 
  power 
  to 
  account 
  and 
  aided 
  in 
  the 
  

   production 
  of 
  narrow 
  canons 
  of 
  great 
  depth. 
  Probably 
  the 
  waters 
  leav- 
  

   ing 
  the 
  glacier 
  had 
  selected 
  the 
  most 
  favorable 
  directions 
  for 
  their 
  pass- 
  

   age, 
  and 
  the 
  ice, 
  with 
  rocks 
  coming 
  after 
  them, 
  wrought 
  so 
  successful 
  an 
  

   erosian 
  that 
  the 
  caiions 
  entered 
  from 
  above 
  are 
  almost 
  impassable. 
  So 
  

   far 
  as 
  I 
  could 
  observe, 
  no 
  striation 
  remains 
  on 
  the 
  walls 
  of 
  the 
  conglom- 
  

   erate, 
  neither 
  do 
  the 
  erratic 
  bowlders 
  within 
  the 
  caiions 
  show 
  any 
  regu- 
  

   lar 
  morainal 
  deposition. 
  The 
  latter 
  dropped 
  down 
  as 
  they 
  were 
  pushed 
  

   over 
  the 
  steep 
  edges 
  by 
  the 
  ice, 
  and 
  merely 
  form 
  irregular 
  heaps, 
  the 
  

   irregularity 
  of 
  which 
  was 
  further 
  increased 
  by 
  the 
  superposition 
  of 
  the 
  

   ice. 
  How 
  far 
  down 
  these 
  caiions 
  the 
  glaciers 
  may 
  have 
  extended 
  I 
  

   am 
  unable 
  to 
  say, 
  but 
  am 
  of 
  the 
  opinion 
  that 
  they 
  soon 
  succumbed 
  to 
  

   the 
  higher 
  temperature 
  that 
  they 
  must 
  have 
  found 
  3,000 
  to 
  3,500 
  feet 
  

   lower. 
  Where 
  the 
  Eio 
  Conejos 
  reaches 
  San 
  Luis 
  Valley, 
  it 
  runs 
  in 
  a 
  

   caiion 
  of 
  basalt. 
  Soil 
  has 
  been 
  deposited 
  on 
  either 
  side 
  of 
  the 
  river 
  by 
  

   it, 
  while 
  the 
  surrounding 
  country 
  shows 
  nothing 
  but 
  the 
  sterile 
  basaltic 
  

   cover. 
  Probably 
  this 
  soil 
  may 
  have 
  been 
  to 
  a 
  great 
  extent 
  the 
  smaller 
  

   detritus 
  formed 
  by 
  the 
  grinding 
  action 
  of 
  the 
  glaciers. 
  Nothing 
  was 
  

   found 
  there, 
  however, 
  that 
  might 
  warrant 
  the 
  belief 
  that 
  any 
  of. 
  the 
  

   glaciers 
  could 
  have 
  reached 
  the 
  valley. 
  Although 
  the 
  pressure 
  from 
  

   above 
  must 
  have 
  been 
  very 
  great 
  and 
  tbe 
  impetus 
  given 
  the 
  motion 
  of 
  

   the 
  glaciers 
  very 
  considerable, 
  by 
  descending 
  so 
  rapidly, 
  it 
  does 
  not 
  seem 
  

   as 
  if 
  they 
  traveled 
  more 
  than 
  perhaps 
  seven 
  or 
  eight 
  miles 
  from 
  the 
  

   point 
  where 
  their 
  western 
  limit 
  may 
  be 
  located. 
  This 
  is 
  the 
  largest 
  

   single 
  glacier 
  or 
  rather 
  series 
  of 
  glaciers 
  from 
  one 
  starting-point 
  that 
  I 
  

   have 
  observed 
  in 
  Southern 
  Colorado, 
  and 
  it 
  is 
  a 
  particularly 
  satisfac- 
  

   tory 
  one, 
  inasmuch 
  as 
  it 
  has 
  left 
  the 
  record 
  of 
  its 
  history 
  in 
  so 
  unequiv- 
  

   ocal 
  and 
  easily 
  read 
  a 
  legend. 
  I 
  call 
  it 
  tbe 
  Conejos 
  glacier. 
  

  

  Small 
  indications 
  of 
  local 
  glacial 
  action 
  may 
  be 
  observed 
  in 
  some 
  of 
  

   the 
  canons 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Eange. 
  They 
  are 
  of 
  such 
  a 
  charac- 
  

   ter 
  as 
  to 
  lead 
  to 
  the 
  conclusion 
  that 
  the 
  same 
  results 
  might 
  have 
  been 
  

   produced 
  by 
  a 
  repeated 
  accumulatiou 
  of 
  snow 
  and 
  the 
  subsequent 
  

   movement 
  of 
  both 
  snow 
  and 
  the 
  adjoining 
  bowlders 
  upou 
  thawing. 
  

   At 
  all 
  events 
  there 
  is 
  no 
  certainty 
  as 
  to 
  their 
  true 
  glacial 
  character, 
  and 
  

   they 
  are 
  not 
  considered 
  here. 
  The 
  above 
  enumeration 
  includes 
  all 
  the 
  

  

  