﻿172 
  J. 
  S. 
  Diller 
  — 
  Crater 
  ZaJce, 
  Oregon, 
  

  

  the 
  products 
  of 
  later 
  volcanic 
  eruptions. 
  We 
  have 
  an 
  excel- 
  

   lent 
  opportunity 
  to 
  study 
  this 
  portion 
  of 
  the 
  pit 
  on 
  Wizard 
  

   Island, 
  where 
  the 
  bottom 
  rises 
  above 
  the 
  surface 
  of 
  the 
  water. 
  

   The 
  island, 
  near 
  the 
  center 
  of 
  the 
  view 
  in 
  plate 
  V, 
  is 
  formed 
  of 
  a 
  

   cinder 
  cone 
  and 
  lava 
  field, 
  which 
  are 
  practically 
  unchanged 
  

   since 
  their 
  recent 
  eruption. 
  

  

  The 
  steep-sloped 
  cinder 
  cone, 
  845 
  feet 
  in 
  height, 
  is 
  sur- 
  

   mounted 
  by 
  a 
  perfect 
  crater 
  80 
  feet 
  in 
  depth. 
  The 
  encircling 
  

   lava 
  field, 
  made 
  up 
  of 
  angular 
  blocks 
  of 
  dark 
  lava 
  broken 
  up 
  

   at 
  the 
  time 
  of 
  the 
  eruption, 
  is 
  rough 
  in 
  the 
  extreme. 
  

  

  Judging 
  from 
  Wizard 
  Island, 
  one 
  might 
  expect 
  that 
  there 
  

   were 
  other 
  piles 
  of 
  recent 
  cinders 
  and 
  lava 
  upon 
  the 
  bottom 
  of 
  

   the 
  pit, 
  and 
  so 
  it 
  seems 
  ; 
  for 
  according 
  to 
  the 
  soundings 
  of 
  the 
  

   lake 
  made 
  by 
  Captain, 
  now 
  Major, 
  Dutton 
  in 
  1886,* 
  there 
  are 
  

   two 
  such 
  prominences 
  rising 
  from 
  great 
  depths, 
  but 
  failing 
  by 
  

   over 
  four 
  hundred 
  feet 
  to 
  reach 
  the 
  surface 
  of 
  the 
  water. 
  The 
  

   eruptions 
  of 
  lava 
  and 
  fragmental 
  material 
  upon 
  the 
  bottom 
  of 
  

   the 
  pit 
  have 
  partially 
  filled 
  it 
  up, 
  but 
  how 
  much 
  has 
  been 
  lost 
  

   in 
  depth 
  by 
  these 
  final 
  outbursts 
  cannot 
  be 
  estimated. 
  

  

  To 
  epitomise 
  : 
  The 
  history 
  of 
  Crater 
  Lake 
  and 
  its 
  rim 
  began 
  

   in 
  the 
  upbuilding, 
  by 
  normal 
  volcanic 
  processes, 
  of 
  a 
  large 
  vol- 
  

   cano, 
  Mt. 
  Mazama, 
  comparable 
  in 
  the 
  nature 
  of 
  its 
  lavas, 
  struc- 
  

   ture 
  and 
  size 
  with 
  the 
  greater 
  peaks 
  of 
  the 
  Cascade 
  Range. 
  

  

  Crater 
  Lake 
  did 
  not 
  then 
  exist. 
  Its 
  site 
  was 
  occupied 
  by 
  

   Mt. 
  Mazama, 
  which 
  was 
  an 
  active 
  volcano 
  in 
  the 
  glacial 
  period. 
  

   Glaciers 
  descended 
  from 
  its 
  higher 
  slopes, 
  scratching 
  the 
  rocks 
  

   and 
  depositing 
  moraines 
  about 
  its 
  base. 
  

  

  The 
  later 
  eruptions 
  of 
  Mt. 
  Mazama 
  occurred 
  in 
  the 
  glacial 
  

   period 
  and 
  doubtless 
  produced 
  extensive 
  floods 
  which 
  filled 
  

   with 
  debris 
  the 
  valleys 
  of 
  all 
  the 
  streams 
  radiating 
  from 
  the 
  

   mountain. 
  

  

  In 
  approximate 
  connection 
  with 
  its 
  final 
  eruption, 
  the 
  molten 
  

   material 
  of 
  the 
  interior 
  withdrawing, 
  the 
  summit 
  of 
  Mt. 
  

   Mazama 
  caved 
  in 
  and 
  sank 
  away, 
  giving 
  rise 
  to 
  a 
  caldera 
  

   nearly 
  six 
  miles 
  in 
  diameter 
  and 
  4,000 
  feet 
  deep. 
  Thus 
  origi- 
  

   nated 
  the 
  great 
  pit 
  in 
  which 
  Crater 
  Lake 
  is 
  contained, 
  encircled 
  

   by 
  a 
  glaciated 
  rim, 
  the 
  hollow 
  base 
  of 
  the 
  engulfed 
  Mt. 
  

   Mazama. 
  

  

  Upon 
  the 
  bottom 
  of 
  the 
  caldera, 
  volcanic 
  activity 
  continued. 
  

   There 
  were 
  new 
  eruptions 
  building 
  up 
  cinder 
  cones 
  and 
  lava- 
  

   fields 
  and 
  partially 
  refilling 
  the 
  great 
  pit. 
  

  

  Precipitation 
  is 
  greater 
  than 
  evaporation 
  in 
  that 
  region. 
  

   Volcanic 
  activity 
  ceasing, 
  the 
  conditions 
  were 
  favorable 
  for 
  

   water 
  accumulation, 
  and 
  Crater 
  Lake 
  was 
  formed 
  in 
  the 
  pit. 
  

  

  Washington, 
  D. 
  C. 
  

  

  * 
  Eighth 
  Annual 
  Report, 
  Part 
  I, 
  pp. 
  157-8. 
  

  

  