﻿168 
  J. 
  S. 
  Diller 
  — 
  Crater 
  Lake, 
  Oregon. 
  

  

  separation 
  between 
  the 
  glacial 
  lobes 
  which 
  descended 
  Anna 
  

   and 
  Castle 
  Creeks 
  on 
  opposite 
  sides 
  of 
  the 
  range. 
  

  

  At 
  many 
  points 
  on 
  the 
  very 
  crest 
  of 
  the 
  rim, 
  glacial 
  debris 
  

   is 
  well 
  exposed, 
  resting 
  on 
  striated 
  rocks. 
  Occasionally 
  the- 
  

   debris 
  is 
  over 
  50 
  feet 
  in 
  thickness, 
  but 
  is 
  rarely 
  composed 
  of 
  

   large 
  fragments. 
  The 
  largest 
  bowlders, 
  about 
  10 
  feet 
  in 
  diam- 
  

   eter, 
  were 
  seen 
  some 
  distance 
  from 
  the 
  crest 
  upon 
  the 
  outer 
  

   side. 
  

  

  Glaciers 
  descended 
  all 
  the 
  valleys 
  upon 
  the 
  outer 
  slope 
  of 
  

   the 
  rim 
  for 
  from 
  two 
  to 
  five 
  miles. 
  Below, 
  the 
  moraines 
  termi- 
  

   nate 
  in 
  plains 
  through 
  which 
  the 
  present 
  streams 
  have 
  cut 
  

   narrow 
  deep 
  canyons 
  with 
  columned 
  slopes 
  or 
  cliffs, 
  rendering 
  

   them 
  inaccessible, 
  Their 
  sculptured 
  walls 
  gave 
  name 
  to 
  

   Castle 
  Creek, 
  but 
  an 
  equally 
  fine 
  display 
  occurs 
  along 
  Anna 
  

   Creek. 
  

  

  Glacial 
  striae 
  are 
  well 
  marked 
  at 
  many 
  points, 
  on 
  the 
  very 
  

   crest 
  of 
  the 
  rim, 
  radiating 
  down 
  the 
  outer 
  slope 
  in 
  some 
  cases 
  

   for 
  a 
  distance 
  of 
  five 
  miles. 
  The 
  slopes 
  were 
  so 
  generally 
  

   covered 
  with 
  moving 
  ice 
  that 
  the 
  outlines 
  of 
  the 
  glaciers 
  were 
  

   not 
  well 
  marked. 
  Probably 
  the 
  largest 
  mass 
  was 
  that 
  of 
  the 
  

   Divide 
  glacier, 
  which 
  had 
  a 
  width 
  of 
  over 
  four 
  miles 
  upon 
  

   what 
  is 
  now 
  the 
  rim 
  of 
  the 
  lake. 
  The 
  main 
  portion 
  descended 
  

   Castle 
  Creek 
  and 
  its 
  branches 
  toward 
  Rogue 
  River, 
  but 
  a 
  large 
  

   lobe 
  extended 
  down 
  Anna 
  Creek 
  on 
  the 
  eastern 
  slope 
  of 
  the- 
  

   range. 
  

  

  A 
  large 
  mass 
  of 
  ice 
  descended 
  the 
  valley 
  next 
  south 
  of 
  Llao 
  

   Rock, 
  reaching 
  far 
  down 
  over 
  the 
  broad 
  stream 
  of 
  basalt 
  from 
  

   Red 
  Cone. 
  The 
  lavas 
  are 
  deeply 
  planed 
  off 
  and 
  striated, 
  but 
  

   the 
  effect 
  of 
  glacial 
  erosion 
  upon 
  the 
  general 
  topography 
  is 
  not 
  

   so 
  marked 
  as 
  upon 
  the 
  southern 
  side 
  of 
  the 
  lake, 
  where 
  deep* 
  

   U-shaped 
  canyons 
  have 
  been 
  cut 
  in 
  the 
  older 
  lavas. 
  

  

  That 
  the 
  volcano 
  was 
  active 
  at 
  intervals 
  during 
  the 
  glacial 
  

   period 
  is 
  well 
  shown 
  by 
  the 
  glaciated 
  flow 
  of 
  Round 
  Top, 
  upon 
  

   the 
  northeastern 
  edge 
  of 
  the 
  rim. 
  This 
  flow 
  is 
  overlain 
  by 
  two 
  

   layers 
  of 
  pumice 
  separated 
  by 
  a 
  sheet 
  of 
  rhyolite, 
  all 
  of 
  which 
  

   were 
  erupted 
  after 
  the 
  glaciation 
  of 
  the 
  surface 
  upon 
  which 
  

   they 
  rest. 
  

  

  The 
  eruption 
  must 
  have 
  been 
  accompanied 
  by 
  great 
  floods 
  

   from 
  the 
  snow-capped 
  mountain. 
  Such 
  floods 
  would 
  account 
  

   for 
  the 
  fact 
  that 
  all 
  the 
  valleys 
  radiating 
  from 
  Crater 
  Lake 
  

   have 
  been 
  extensively 
  filled 
  with 
  sediments. 
  

  

  Reference 
  has 
  already 
  been 
  made 
  to 
  the 
  occurrence 
  of 
  gla- 
  

   cial 
  striae 
  on 
  the 
  very 
  crest 
  of 
  the 
  rim. 
  They 
  may 
  be 
  seen 
  in 
  

   many 
  places 
  along 
  the 
  crest 
  northwest 
  of 
  Victor 
  Rock 
  ; 
  also 
  a 
  

   few 
  miles 
  beyond, 
  in 
  the 
  sag 
  of 
  the 
  rim 
  next 
  southwest 
  of 
  

   Llao 
  Rock, 
  as 
  well 
  as 
  near 
  its 
  summit. 
  They 
  occur 
  also 
  in 
  

   Round 
  Top, 
  in 
  Kerr 
  Notch 
  and 
  over 
  Eagle 
  Crags, 
  completing 
  

  

  