﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  

  

  II 
  

  

  igneous 
  activity 
  in 
  general. 
  By 
  this 
  means 
  materials 
  are 
  brought 
  

   up 
  from 
  within 
  the 
  earth 
  to 
  or 
  near 
  its 
  surface. 
  Thus 
  an 
  active 
  

   volcano 
  violently 
  ejects 
  rock 
  fragments, 
  dust 
  etc. 
  or 
  more 
  quietly 
  

   pours 
  out 
  molten 
  rock, 
  while 
  an 
  many 
  cases 
  great 
  masses 
  of 
  molten 
  

   rocks 
  have 
  been 
  forced 
  upward 
  into 
  the 
  crust 
  of 
  the 
  earth 
  without 
  

   reaching 
  the 
  surface 
  and 
  hence 
  have 
  slowly 
  cooled 
  at 
  greater 
  or 
  

   lesser 
  depths 
  below 
  the 
  surface. 
  Such 
  volcanic 
  rocks 
  have 
  become 
  

   exposed 
  to 
  view 
  only 
  by 
  subsequent 
  erosion 
  of 
  the 
  region. 
  

  

  In 
  order 
  to 
  understand 
  the 
  physical 
  history 
  of 
  our 
  State 
  it 
  is 
  

   necessary 
  to 
  know 
  that 
  significant 
  changes, 
  like 
  those 
  above 
  

   described, 
  have 
  long 
  been, 
  and 
  now 
  are 
  taking 
  place. 
  In 
  tracing 
  

   this 
  history 
  we 
  shall 
  see 
  how 
  all 
  these 
  natural 
  processes 
  have 
  

   operated 
  to 
  bring 
  the 
  State 
  into 
  its 
  present 
  condition. 
  It 
  is 
  also 
  

   necessary 
  to 
  understand 
  that 
  the 
  known 
  history 
  of 
  the 
  earth 
  has 
  

   been 
  carefully 
  divided 
  into 
  great 
  eras, 
  and 
  into 
  lesser 
  periods 
  and 
  

   epochs, 
  and 
  that 
  these 
  constitute 
  what 
  is 
  called 
  the 
  geologic 
  time 
  

   scale. 
  This 
  time 
  scale 
  is 
  important 
  to 
  the 
  reader 
  because 
  the 
  prin- 
  

   cipal 
  events 
  in 
  the 
  history 
  of 
  the 
  State 
  will 
  be 
  taken 
  up, 
  so 
  far 
  as 
  

   they 
  are 
  recorded, 
  in 
  regular 
  order 
  according 
  to 
  that 
  scale. 
  In 
  the 
  

   first 
  table 
  the 
  names 
  of 
  eras 
  and 
  periods 
  are 
  mostly 
  of 
  world-wide 
  

   usage, 
  while 
  the 
  names 
  of 
  subdivisions 
  (epochs) 
  of 
  the 
  periods 
  are 
  

   much 
  more 
  local 
  in 
  usage 
  and, 
  in 
  the 
  second 
  table, 
  only 
  those 
  are 
  

   given 
  which 
  apply 
  to 
  New 
  York 
  State. 
  

  

  Geologic 
  Time 
  Scale 
  

  

  eras 
  

   Cenozoic 
  

  

  Mesozoic 
  

  

  ,cj 
  

  

  Paleozoic 
  

  

  Proterozoic 
  

   Archeozoic 
  

  

  PERIODS 
  

  

  Quaternary 
  

  

  Tertiary 
  

  

  Cretacic 
  

   Jurassic 
  

  

  Triassic 
  

  

  Permic 
  

  

  Carbonic 
  

  

  Devonic 
  

  

  Siluric 
  

  

  Ordovicic 
  

  

  Cambric 
  

   Algonkic 
  

   Archean 
  

  

  } 
  

  

  DOMINANT 
  LIFE 
  

  

  Age 
  of 
  man 
  

  

  Age 
  of 
  mammals 
  

  

  Age 
  of 
  reptiles, 
  with 
  birds 
  first 
  in 
  

   the 
  Jurassic, 
  and 
  trees 
  and 
  flowers 
  

   of 
  modern 
  aspect 
  first 
  in 
  the 
  Cre- 
  

   tacic 
  

  

  Age 
  of 
  amphibians, 
  with 
  cycad 
  plants 
  

   common 
  

  

  Great 
  coal 
  age, 
  with 
  large 
  nonflower- 
  

   ing 
  plants 
  

  

  Age 
  of 
  fishes 
  

  

  Age 
  of 
  invertebrates, 
  with 
  some 
  very 
  

   simple 
  fishes 
  in 
  the 
  Siluric 
  

  

  Earliest 
  known 
  forms 
  of 
  life 
  

   but 
  records 
  very 
  imperfect 
  

  

  