﻿G. 
  FI. 
  Stone 
  — 
  Glaciation 
  of 
  Central 
  Idaho. 
  

  

  Art. 
  II. 
  — 
  Note 
  on 
  the 
  Glaciation 
  of 
  Central 
  Idaho 
  ; 
  by 
  

   George 
  H. 
  Stone. 
  

  

  Central 
  Idaho 
  is 
  rugged 
  and 
  mountainous, 
  a 
  succession 
  of 
  

   dark 
  green 
  and 
  blue 
  forested 
  ranges. 
  The 
  rocks 
  are 
  mostly 
  

   granites, 
  schists, 
  and 
  quartzites, 
  which 
  in 
  different 
  regions 
  vary 
  

   greatly 
  in 
  capacity 
  to 
  withstand 
  weathering 
  and 
  erosion. 
  The 
  

   larger 
  streams 
  flow 
  in 
  deep, 
  canon-like 
  valleys, 
  which 
  broaden 
  

   into 
  plains 
  in 
  places 
  where 
  the 
  rocks 
  are 
  easily 
  disintegrated. 
  

   Several 
  of 
  the 
  principal 
  watersheds 
  consist 
  of 
  rolling 
  plateaus 
  

   but 
  little 
  dissected 
  by 
  erosion. 
  They 
  appear 
  to 
  be 
  remains 
  of 
  

   what 
  was 
  once 
  a 
  large 
  plain-like 
  plateau 
  and 
  have 
  an 
  elevation 
  

   of 
  7,000 
  to 
  8,000 
  feet 
  above 
  the 
  sea. 
  Approaching 
  the 
  larger 
  

   rivers, 
  welind 
  the 
  slopes 
  becoming 
  steeper 
  and 
  the 
  whole 
  coun- 
  

   try 
  deeply 
  dissected 
  and 
  accentuated 
  by 
  erosion, 
  until 
  we 
  reach 
  

   the 
  principal 
  rivers, 
  the 
  Snake 
  and 
  the 
  Salmon, 
  flowing 
  in 
  

   valleys 
  of 
  erosion 
  6,000 
  or 
  more 
  feet 
  in 
  depth. 
  A 
  few 
  ranges 
  

   appear 
  to 
  have 
  been 
  raised 
  above 
  the 
  adjacent 
  parts 
  and 
  are 
  

   mountains 
  of 
  upheaval. 
  During 
  glacial 
  time 
  the 
  relief 
  forms 
  

   of 
  the 
  land 
  were 
  substantially 
  the 
  same 
  as 
  at 
  present. 
  All 
  of 
  

   the 
  large 
  ranges 
  and 
  many 
  of 
  the 
  peaks 
  now 
  having 
  an 
  eleva- 
  

   tion 
  of 
  about 
  6,000 
  feet 
  shows 
  signs 
  of 
  extinct 
  glaciers. 
  The 
  

   geographical 
  position 
  of 
  Idaho 
  with 
  respect 
  both 
  to 
  the 
  Pacific 
  

   Ocean 
  and 
  the 
  vast 
  Canadian 
  areas 
  of 
  extreme 
  winter 
  cold, 
  is 
  

   favorable 
  to 
  a 
  large 
  snowfall, 
  both 
  now 
  and 
  at 
  all 
  times 
  since 
  

   the 
  rise 
  of 
  the 
  continent 
  above 
  the 
  ocean. 
  The 
  following 
  per- 
  

   sonal 
  observations 
  were 
  made 
  by 
  the 
  writer 
  during 
  a 
  recent 
  

   reconnoissance. 
  

  

  The 
  mountain 
  ranges 
  that 
  form 
  the 
  watersheds 
  between 
  the 
  

   Boise, 
  Payette, 
  and 
  Salmon 
  rivers 
  formed 
  the 
  gathering 
  ground 
  

   of 
  numerous 
  local 
  glaciers. 
  Those 
  which 
  flowed 
  south 
  and 
  

   west 
  down 
  the 
  valleys 
  of 
  the 
  Boise 
  and 
  the 
  Payette 
  ended 
  at 
  

   not 
  far 
  from 
  5,000 
  feet 
  elevation. 
  Those 
  flowing 
  north 
  and 
  

   east 
  down 
  the 
  valleys 
  of 
  the 
  South 
  and 
  Middle 
  Forks 
  of 
  the 
  

   Salmon 
  reached 
  a 
  somewhat 
  lower 
  elevation, 
  but 
  none 
  of 
  them 
  

   reached 
  so 
  low 
  an 
  altitude 
  as 
  the 
  main 
  Salmon 
  river, 
  which 
  in 
  

   this 
  part 
  of 
  its 
  course 
  has 
  an 
  elevation 
  of 
  less 
  than 
  1,000 
  feet. 
  

   From 
  the 
  east 
  and 
  west 
  divide 
  between 
  the 
  Salmon 
  and 
  the 
  

   Clearwater, 
  local 
  glaciers 
  flowed 
  south 
  into 
  the 
  gorge 
  of 
  the 
  

   Salmon, 
  but 
  none 
  appear 
  to 
  have 
  reached 
  that 
  river. 
  From 
  

   this 
  same 
  divide 
  glaciers 
  flowed 
  north 
  to 
  the 
  South 
  Fork 
  of 
  the 
  

   Clearwater. 
  The 
  broad 
  valleys 
  of 
  both 
  the 
  South 
  and 
  Middle 
  

   Forks 
  of 
  the 
  Clearwater 
  were 
  covered 
  by 
  valley 
  glaciers, 
  i. 
  e., 
  

   the 
  local 
  glaciers 
  that 
  originated 
  in 
  the 
  Bitter 
  Root 
  range 
  and 
  

   the 
  higher 
  ranges 
  that 
  form 
  the 
  rims 
  of 
  these 
  basins 
  united 
  to 
  

  

  