﻿COMPONENTS 
  OF 
  THE 
  EARTH 
  S 
  CKCST, 
  MINERALS 
  AND 
  ROCKS 
  

  

  Rocks 
  

  

  123 
  

  

  These 
  are 
  the 
  materials 
  of 
  the 
  strata 
  and 
  other 
  masses 
  which 
  

   form 
  integral 
  parts 
  of 
  the 
  earth's 
  crust. 
  They 
  may 
  be 
  classified 
  

   as 
  massive 
  or 
  igneous, 
  sedimentary 
  and 
  metamorphic. 
  The 
  re- 
  

   lations 
  of 
  these 
  three 
  natural 
  groups 
  may 
  be 
  shown 
  by 
  a 
  trian- 
  

   gular 
  diagram, 
  as 
  follows: 
  

  

  Massive 
  

  

  or 
  

   Igneous 
  

  

  Sedimentary 
  

   or 
  

   stratified 
  

  

  by 
  heat 
  and 
  pressure 
  > 
  

  

  -< 
  by 
  erosion 
  and 
  deposition 
  

  

  Metamorphic 
  

  

  This 
  is 
  meant 
  to 
  show 
  that 
  an 
  igneous 
  rock 
  may, 
  by 
  erosion, 
  

   be 
  reduced 
  to 
  sediment 
  and 
  laid 
  down 
  in 
  beds, 
  or 
  by 
  heat 
  and 
  

   pressure 
  may 
  be 
  metamorphosed 
  from 
  its 
  original 
  massive 
  con- 
  

   dition 
  and 
  become 
  schistose. 
  A 
  sedimentary 
  rock 
  may 
  also 
  pass 
  

   through 
  the 
  metamorphic 
  condition, 
  become 
  fused 
  and 
  enter 
  the 
  

   igneous 
  state. 
  A 
  metamorphic 
  rock 
  may 
  arrive 
  at 
  the 
  igneous 
  

   condition 
  by 
  heat 
  and 
  pressure? 
  or 
  may 
  become 
  sedimentary 
  

   through 
  erosion 
  and 
  deposition. 
  

  

  