﻿OCEANOGRAPHY 
  — 
  STETSON 
  229 
  

  

  RECENT 
  ADVANCES 
  IN 
  SUBMARINE 
  GEOLOGY 
  

   INTRODUCTION 
  

  

  The 
  student 
  of 
  submarine 
  geology, 
  except 
  in 
  the 
  field 
  of 
  sedimenta- 
  

   tion, 
  tries 
  to 
  attain 
  the 
  same 
  objectives 
  that 
  are 
  pursued 
  ashore. 
  

   The 
  difficulties 
  arise 
  in 
  adapting 
  the 
  various 
  land 
  techniques 
  to 
  

   marine 
  conditions, 
  and 
  in 
  handling 
  the 
  necessary 
  gear 
  on 
  shipboard. 
  

   Whatever 
  the 
  objective, 
  it 
  is 
  subject 
  to 
  the 
  limitations 
  that 
  a 
  ship 
  

   imposes, 
  and 
  the 
  first 
  thing 
  which 
  an 
  oceanographer 
  must 
  realize, 
  no 
  

   matter 
  what 
  his 
  field 
  of 
  endeavor, 
  is 
  that 
  it 
  is 
  impossible 
  to 
  work 
  

   with 
  the 
  same 
  precision 
  that 
  is 
  attainable 
  ashore. 
  This 
  is 
  a 
  perfectly 
  

   valid 
  objection, 
  but, 
  if 
  it 
  were 
  heeded, 
  no 
  oceanographic 
  work 
  of 
  any 
  

   kind 
  would 
  ever 
  be 
  undertaken. 
  

  

  MODERN 
  MARINE 
  SURVEYING 
  

  

  The 
  prime 
  requisite 
  for 
  most 
  geological 
  undertakings 
  is 
  a 
  good 
  

   map 
  ; 
  therefore, 
  let 
  us 
  first 
  take 
  up 
  modern 
  developments 
  in 
  chart- 
  

   ing 
  the 
  ocean 
  bottom. 
  As 
  we 
  have 
  seen, 
  until 
  comparatively 
  re- 
  

   cently 
  deep-water 
  soundings 
  were 
  taken 
  with 
  small-diameter 
  wire 
  

   and 
  a 
  sinker, 
  and, 
  although 
  the 
  machines 
  for 
  handling 
  the 
  wire 
  had 
  

   been 
  improved 
  to 
  a 
  point 
  where 
  the 
  operation 
  was 
  vastly 
  less 
  time- 
  

   consuming 
  than 
  during 
  the 
  early 
  period 
  when 
  hemp 
  was 
  used, 
  never- 
  

   theless, 
  accurate 
  soundings 
  could 
  be 
  obtained 
  only 
  during 
  good 
  

   weather, 
  and 
  in 
  any 
  event 
  the 
  ship 
  had 
  to 
  be 
  stopped. 
  Modern 
  echo 
  

   sounding 
  has 
  come 
  into 
  general 
  use 
  only 
  since 
  World 
  War 
  I. 
  

   Although 
  prior 
  to 
  this 
  date 
  attempts 
  had 
  been 
  made 
  to 
  locate 
  ice- 
  

   bergs 
  by 
  this 
  method, 
  its 
  value 
  in 
  the 
  detection 
  of 
  submarines 
  led 
  

   to 
  more 
  intensive 
  experiments. 
  The 
  term 
  "echo 
  sounding" 
  is 
  practi- 
  

   cally 
  self-explanatory. 
  The 
  recording 
  instrument 
  measures 
  the 
  travel 
  

   time 
  of 
  the 
  sound 
  wave 
  through 
  the 
  water 
  from 
  the 
  ship 
  to 
  the 
  

   bottom 
  and 
  back 
  again, 
  translated 
  into 
  terms 
  of 
  distance. 
  As 
  the 
  

   velocity 
  of 
  sound 
  through 
  water 
  varies 
  somewhat 
  with 
  the 
  density, 
  

   it 
  is 
  necessary 
  to 
  make 
  temperature 
  and 
  salinity 
  observations 
  in 
  the 
  

   different 
  water 
  masses 
  for 
  accurate 
  soundings. 
  Many 
  types 
  of 
  in- 
  

   struments 
  have 
  been 
  developed, 
  and 
  it 
  is 
  not 
  necessary 
  to 
  go 
  into 
  the 
  

   details 
  of 
  their 
  construction 
  here. 
  With 
  the 
  earlier 
  models 
  it 
  was 
  

   necessary 
  to 
  read 
  off 
  each 
  individual 
  sounding, 
  but 
  recently 
  they 
  

   have 
  been 
  made 
  self-recording. 
  The 
  tremendous 
  advantages 
  of 
  this 
  

   machine 
  are 
  that 
  the 
  surveying 
  vessel 
  can 
  sound 
  continuously 
  while 
  

   steaming 
  at 
  full 
  speed, 
  accurately, 
  and 
  in 
  comparative 
  independence 
  

   of 
  the 
  weather. 
  To 
  quote 
  Capt. 
  G. 
  T. 
  Kude 
  (Geophysical 
  Explora- 
  

   tion 
  of 
  the 
  Ocean 
  Bottom, 
  1937, 
  pp. 
  10-11) 
  : 
  

  

  * 
  * 
  * 
  in 
  15 
  working 
  days 
  in 
  the 
  month 
  of 
  July 
  1937, 
  the 
  party 
  on 
  the 
  Coast 
  

   and 
  Geodetic 
  Survey 
  Ship 
  Lydonia 
  recorded 
  12,489 
  soundings 
  of 
  the 
  continental 
  

   566766 
  — 
  44 
  16 
  

  

  