﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  107 
  

  

  In 
  many 
  cases 
  where 
  the 
  edge 
  of 
  an 
  ice 
  lobe 
  extended 
  across 
  the 
  

   mouth 
  of 
  an 
  east, 
  or 
  west, 
  or 
  even 
  south-sloping 
  valley, 
  glacial 
  

   lakes 
  were 
  formed. 
  A 
  fine 
  example 
  of 
  a 
  glacial 
  lake 
  (now 
  extinct) 
  

   formed 
  in 
  a 
  south-sloping 
  valley 
  has 
  been 
  called 
  glacial 
  Lake 
  Sacan- 
  

   daga 
  which 
  covered 
  many 
  square 
  miles 
  of 
  the 
  bottom 
  of 
  the 
  broad, 
  

   deep 
  valley 
  in 
  which 
  Johnstown, 
  Gloversville, 
  and 
  Northville 
  are 
  

   located. 
  Through 
  this 
  valley, 
  which 
  has 
  a 
  width 
  of 
  several 
  miles 
  

   and 
  a 
  maximum 
  depth 
  of 
  over 
  a 
  thousand 
  feet, 
  the 
  preglacial 
  

   Sacandaga 
  flowed 
  southward 
  into 
  the 
  Mohawk. 
  During 
  the 
  gen- 
  

   eral 
  ice 
  retreat, 
  but 
  when 
  -the 
  Mohawk 
  glacial 
  lobe 
  was 
  still 
  present, 
  

   morainic 
  deposits 
  along 
  the 
  margin 
  of 
  the 
  ice 
  lobe 
  formed 
  an 
  

   effective 
  barrier 
  across 
  the 
  mouth 
  of 
  the 
  valley 
  thus 
  ponding 
  the 
  

   waters 
  over 
  the 
  valley 
  bottom 
  and 
  causing 
  the 
  Sacandaga 
  to 
  find 
  

   an 
  outlet 
  northeastward 
  over 
  the 
  low 
  divide 
  at 
  Conklingville. 
  The 
  

   altitude 
  of 
  the 
  lake 
  corresponded 
  approximately 
  with 
  the 
  present 
  

   780 
  foot 
  contour 
  line, 
  though 
  it 
  is 
  quite 
  certain 
  that 
  the 
  land 
  was 
  

   then 
  somewhat 
  lower. 
  This 
  lake 
  persisted 
  for 
  a 
  good 
  while 
  after 
  

   the 
  disappearance 
  of 
  the 
  ice 
  because 
  of 
  the 
  effective 
  drift 
  dam, 
  

   and 
  even 
  today, 
  in 
  the 
  spring 
  of 
  the 
  year, 
  a 
  number 
  of 
  square 
  miles 
  

   of 
  swamp 
  in 
  the 
  lowest 
  part 
  of 
  the 
  valley 
  are 
  flooded. 
  The 
  lake 
  

   was 
  drained 
  by 
  cutting 
  down 
  the 
  divide 
  at 
  Conklingville. 
  It 
  is 
  

   interesting 
  to 
  note 
  in 
  passing 
  that 
  the 
  construction 
  of 
  the 
  proposed 
  

   Sacandaga 
  reservoir, 
  by 
  means 
  of 
  a 
  dam 
  at 
  Conklingville, 
  would 
  

   almost 
  exactly 
  restore 
  this 
  former 
  glacial 
  lake. 
  

  

  Many 
  other 
  glacial 
  lakes 
  are 
  known 
  to 
  have 
  been 
  formed 
  by 
  

   ponding 
  of 
  water 
  alongside 
  the 
  waning 
  Mohawk 
  ice 
  lobe. 
  During 
  

   the 
  melting 
  of 
  the 
  ice 
  tongue 
  from 
  the 
  Hudson 
  and 
  Champlaiu 
  

   valleys, 
  many 
  small 
  glacial 
  lakes 
  are 
  also 
  known 
  to 
  have 
  been 
  

   formed 
  in 
  the 
  tributary 
  valleys 
  because 
  of 
  ice 
  dams 
  across 
  them. 
  

  

  New 
  York 
  State 
  fairly 
  abounds 
  in 
  such 
  extinct 
  glacial 
  lakes, 
  and 
  

   though 
  comparatively 
  few 
  have 
  yet 
  been 
  described, 
  they 
  are 
  usually 
  

   easily 
  recognizable 
  by 
  means 
  of 
  the 
  typical, 
  flat-topped, 
  delta 
  

   deposits 
  of 
  crudely 
  stratified 
  sands, 
  gravels 
  and 
  clays. 
  

  

  Drainage 
  changes, 
  gorges, 
  and 
  waterfalls. 
  Along 
  with 
  its 
  

   lakes, 
  New 
  York 
  State 
  is 
  also 
  famous 
  for 
  its 
  numerous 
  gorges 
  and 
  

   waterfalls, 
  which 
  are 
  also 
  largely 
  due 
  to 
  the 
  great 
  Ice 
  age. 
  As 
  a 
  

   result 
  of 
  the 
  very 
  long 
  preglacial 
  erosion 
  period, 
  it 
  is 
  perfectly 
  

   clear 
  that 
  typical, 
  steep-sided, 
  narrow 
  gorges 
  and 
  true 
  waterfalls 
  

   must 
  have 
  been 
  very 
  uncommon, 
  if 
  present 
  at 
  all. 
  Like 
  lakes, 
  such 
  

   features 
  are 
  ephemeral 
  because, 
  under 
  our 
  conditions 
  of 
  climate, 
  

   gorges 
  soon 
  (geologically) 
  widen 
  at 
  the 
  top 
  and 
  waterfalls 
  dis- 
  

   appear 
  by 
  retreat 
  or 
  by 
  wearing 
  away 
  the 
  hard 
  rock 
  over 
  which 
  

   they 
  fall. 
  

  

  