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of ash and pumice as a result of the contact of magma with sea water. This 
soft cone is easily eroded hy the sea when the peak reaches sea level. A 
shieldshaped dome is built from thin sheets of highly fluid olivine basalts 
once the cone reaches sea level. The Volcano gradually collapses over the 
vent areas to form a caldera on the summit, and as fresh laVa pours from 
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the cone this caldera is obliterated. Erosion partly destroys the volcanic 
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dome, and submergence may drown the dome and provide an environment suited 
to the development of coral reefs. Rejuvenation of volcanic activity may 
destroy coraline growth and the island may continue to emerge, as in the 
case of the main islands. Or submergenceo or erosion may continue with 
the subsequent development of an atoll. 
Erosion hy wind, waves and rain reached its maximum in the fluctuating 
seas of the Pleistocene, when geological evidence suggests that the sea may 
have been 1000 feet lower than it is today (Zimmerman, 0 £. cit.). When the 
sea-rose slowly as the glaciers receded a littoral environment suitable for 
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uhe growth of coral was provided by the eroded mountain peak. Coral growth 
is limited by depth due to light and oxygen requirements (Wiens, 196*0, 30 
■char growth had to keep pace with the rising sea to survive. At equilibrium 
a rim Of coral remained, enclosing a lagoon on top of the peak, and larger 
areas of coraline growth could then erode and begin the long process of 
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soil formation and plant establishment that has created the existing islands 
of the Leeward Chain. 
Soils on 'Lisianski range from pure sand and coraline gravel on the 
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beaches, through coarse coral rock areas above the beach zone, to humus- 
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sandy mixtures in the vegetated areas. Elschner (o£. cit.) reported that 
the surface was bleached sand to four or five centimeters, and that the 
deeper strata were moist and gray. There are no more recent soil determinations 
