﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  

  

  QUATERNARY 
  PERIOD, 
  INCLUDING 
  NEW 
  YORK 
  IN 
  THE 
  

  

  GREAT 
  ICE 
  AGE 
  

  

  The 
  fact 
  of 
  the 
  Ice 
  age. 
  The 
  Quaternary 
  is 
  the 
  last 
  great 
  period 
  

   of 
  earth 
  history, 
  and 
  it 
  still 
  continues 
  for 
  it 
  has 
  led 
  up 
  to 
  the 
  present- 
  

   day 
  conditions. 
  This 
  period 
  was 
  ushered 
  in 
  by 
  the 
  spreading 
  of 
  

   vast 
  ice 
  sheets 
  over 
  much 
  of 
  northern 
  North 
  America 
  and 
  Europe, 
  

   which 
  must 
  take 
  rank 
  as 
  one 
  of 
  the 
  most 
  interesting 
  and 
  remark- 
  

   able 
  occurrences 
  of 
  geological 
  time. 
  On 
  first 
  thought 
  the 
  existence 
  

   of 
  such 
  vast 
  ice 
  sheets 
  seems 
  unbelievable, 
  but 
  the 
  Ice 
  age 
  occurred 
  

   so 
  short 
  a 
  time 
  ago 
  that 
  the 
  records 
  of 
  the 
  event 
  are 
  perfectly 
  clear 
  

   and 
  conclusive. 
  The 
  fact 
  of 
  this 
  great 
  Ice 
  age 
  was 
  discovered 
  by 
  

   Louis 
  Agassiz 
  in 
  1837, 
  and 
  fully 
  announced 
  before 
  the 
  British 
  

   Scientific 
  Association 
  in 
  1840. 
  For 
  some 
  years 
  the 
  idea 
  was 
  

   opposed, 
  especially 
  by 
  advocates 
  of 
  the 
  so-called 
  iceberg 
  theory. 
  

   Now, 
  however, 
  no 
  important 
  event 
  of 
  earth 
  history 
  is 
  more 
  firmly 
  

   established 
  and 
  no 
  student 
  of 
  the 
  subject 
  ever 
  questions 
  the 
  fact 
  

   of 
  the 
  Quaternary 
  Ice 
  age. 
  

  

  Some 
  of 
  the 
  proofs 
  of 
  the 
  former 
  presence 
  of 
  the 
  great 
  ice 
  sheet 
  

   are 
  as 
  follows: 
  (1) 
  polished 
  and 
  striated 
  rock 
  surfaces 
  (see 
  plate 
  

   39) 
  which 
  are 
  precisely 
  like 
  those 
  produced 
  by 
  existing 
  glaciers, 
  

   and 
  which 
  could 
  not 
  possibly 
  have 
  been 
  produced 
  by 
  any 
  other 
  

   agency; 
  (2) 
  glacial 
  boulders 
  or 
  "erratics" 
  which 
  are 
  often 
  some- 
  

   what 
  rounded 
  and 
  scratched, 
  and 
  which 
  have 
  often 
  been 
  trans- 
  

   ported 
  many 
  miles* 
  from 
  their 
  parent 
  rock 
  ledges; 
  (3) 
  true 
  glacial 
  

   moraines, 
  especially 
  terminal 
  moraines, 
  like 
  that 
  which 
  extends 
  the 
  

   full 
  length 
  of 
  Long 
  Island 
  and 
  marks 
  the 
  southernmost 
  limit 
  of 
  

   the 
  great 
  ice 
  sheet; 
  and 
  (4) 
  the 
  generally 
  widespread 
  distribution 
  

   over 
  most 
  of 
  the 
  glaciated 
  area 
  of 
  heterogeneous 
  glacial 
  debris, 
  both 
  

   unstratified 
  and 
  stratified, 
  which 
  is 
  clearly 
  transported 
  material 
  and 
  

   typically 
  rests 
  upon 
  the 
  bedrock 
  by 
  sharp 
  contact. 
  

  

  Ice 
  extent 
  and 
  centers 
  of 
  accumulation. 
  The 
  best 
  known 
  exist- 
  

   ing 
  great 
  ice 
  sheets 
  are 
  those 
  of 
  Greenland 
  and 
  Anarctica, 
  especially 
  

   the 
  former 
  which 
  covers 
  about 
  500,000 
  square 
  miles. 
  This 
  glacier 
  

   is 
  so 
  large 
  and 
  deep 
  that 
  only 
  an 
  occasional 
  high 
  rocky 
  mountain 
  

   projects 
  above 
  its 
  surface, 
  and 
  the 
  ice 
  is 
  known 
  to 
  be 
  slowly 
  moving 
  

   outward 
  in 
  all 
  directions 
  from 
  the 
  interior 
  to 
  the 
  margins 
  of 
  Green- 
  

   land. 
  Along 
  the 
  margins, 
  where 
  melting 
  is 
  more 
  rapid, 
  some 
  land 
  

   is 
  exposed, 
  but 
  often 
  the 
  ice 
  flows 
  out 
  into 
  the 
  ocean 
  where 
  it 
  

   breaks 
  off 
  to 
  form 
  large 
  icebergs. 
  

  

  The 
  accompanying 
  map 
  (figure 
  29) 
  shows 
  the 
  area 
  of 
  nearly 
  

   4,000,000 
  square 
  miles 
  of 
  North 
  America 
  covered 
  by 
  ice 
  at 
  the 
  

  

  