﻿344 
  W. 
  G. 
  Foye 
  — 
  Geology 
  of 
  the 
  Lau 
  Islands, 
  

  

  Previous 
  Work. 
  

  

  J. 
  Stanley 
  Gardiner* 
  of 
  Cambridge 
  University, 
  England, 
  

   E. 
  C. 
  Andrewsf 
  of 
  Sydney, 
  Australia, 
  Alexander 
  Agassiz,J 
  

   and 
  W. 
  M. 
  Davis§ 
  are 
  the 
  scientists 
  who 
  have 
  contributed 
  the 
  

   most 
  to 
  the 
  geological 
  knowledge 
  of 
  the 
  islands. 
  

  

  General 
  Statement 
  of 
  the 
  Results. 
  

  

  The 
  Lau 
  islands 
  are 
  believed 
  to 
  have 
  been 
  formed 
  by 
  

   volcanic 
  activity 
  about 
  the 
  middle 
  of 
  the 
  Tertiary 
  period. 
  

   They 
  were 
  later 
  maturely 
  eroded, 
  submerged, 
  and 
  overlain 
  

   unconformably 
  by 
  300 
  to 
  500 
  feet 
  of 
  coraliferous 
  limestone. 
  

   Still 
  later 
  they 
  were 
  elevated, 
  eroded, 
  and 
  a 
  second 
  period 
  of 
  

   basaltic 
  eruptivity 
  spread 
  its 
  debris 
  over 
  the 
  eroded 
  complex. 
  

   In 
  Recent 
  times 
  certain 
  of 
  the 
  islands 
  in 
  which 
  limestones 
  are 
  

   alone 
  exposed 
  have 
  been 
  eroded 
  to 
  submerged 
  platforms 
  by 
  

   atmospheric 
  solution 
  and, 
  aided 
  by 
  a 
  recent 
  subsidence, 
  atolls 
  

   have 
  developed 
  in 
  their 
  place. 
  

  

  Classification 
  of 
  the 
  Islands. 
  

  

  In 
  a 
  later 
  paper 
  a 
  genetic 
  classification 
  of 
  the 
  Lau 
  islands 
  

   will 
  be 
  given, 
  but 
  for 
  the 
  purposes 
  of 
  this 
  paper 
  it 
  is 
  sufficient 
  

   to 
  distinguish 
  : 
  

  

  1 
  — 
  Islands 
  composed 
  of 
  limestone 
  and 
  volcanic 
  rocks 
  ; 
  

   2 
  — 
  Islands 
  composed 
  of 
  limestone 
  alone 
  ; 
  

   3 
  — 
  Islands 
  composed 
  of 
  volcanic 
  rocks 
  alone. 
  

  

  The 
  members 
  of 
  group 
  3 
  are 
  in 
  general 
  younger 
  than 
  the 
  

   other 
  groups 
  and 
  only 
  two 
  islands, 
  Munia 
  and 
  Kanathea, 
  were 
  

   visited. 
  Among 
  the 
  more 
  important 
  members 
  of 
  group 
  1, 
  

   the 
  Exploring 
  Group, 
  Tuvutha, 
  Lakemba, 
  Ono-i-Lau, 
  and 
  

   Kambara 
  were 
  studied. 
  Fulanga, 
  Ongea, 
  Yatoa, 
  Wangava, 
  

   and 
  Vekai 
  of 
  group 
  2 
  were 
  also 
  visited. 
  Of 
  the 
  islands 
  just 
  

   mentioned, 
  Yanua 
  Mbalavu 
  of 
  the 
  Exploring 
  Group 
  and 
  

   Lakemba 
  will 
  alone 
  be 
  described. 
  The 
  geological 
  facts 
  charac- 
  

   teristic 
  of 
  these 
  islands 
  may 
  be 
  considered 
  as 
  typical 
  of 
  the 
  

   other 
  islands 
  as 
  well. 
  

  

  Detailed 
  Geology. 
  

  

  1. 
  Yanua 
  Mbalavu 
  (fig. 
  1). 
  

  

  Yanua 
  Mbalavu 
  is 
  nearly 
  twenty 
  miles 
  long 
  from 
  ^N. 
  to 
  S. 
  

   and 
  of 
  variable 
  width. 
  It 
  is 
  shaped 
  something 
  like 
  a 
  question 
  

   mark 
  and 
  has 
  its 
  greatest 
  width 
  (2 
  to 
  3 
  miles) 
  near 
  the 
  center 
  

  

  * 
  J. 
  Stanley 
  Gardiner, 
  " 
  Coral 
  Eeefs 
  of 
  Funafuti, 
  Rotunia, 
  and 
  Fiji," 
  Proc. 
  

   Camb. 
  Phil. 
  Soc, 
  vol. 
  ix, 
  pt. 
  8, 
  pp. 
  417-503. 
  1898. 
  

  

  + 
  E. 
  C. 
  Andrews, 
  "Limestones 
  of 
  the 
  Fiji 
  Islands," 
  Bull. 
  Mns. 
  Comp. 
  

   Zool., 
  Harvard 
  College, 
  vol. 
  xxxviii, 
  1900. 
  

  

  :{: 
  Alexander 
  Agassiz, 
  " 
  Coral 
  Reefs 
  of 
  Fiji," 
  Bull. 
  Mus. 
  Comp. 
  Zool., 
  Har- 
  

   vard 
  College, 
  vol. 
  xxxiii, 
  1899. 
  

  

  § 
  W. 
  M. 
  Davis, 
  " 
  A 
  Shaler 
  Memorial 
  Study 
  of 
  Coral 
  Reefs," 
  this 
  Journal, 
  

   vol. 
  xl, 
  pp. 
  223-271, 
  1915. 
  

  

  