Shores and Islands 
The shores of the ocean represent fairly complex geologi- 
cal processes. Before we treat the shores themselves it will be 
wise to mention the different kinds of rocks which are likely 
to occur on them. Rocks are classified under three chief 
headings: igneous, sedimentary, and metamorphic rocks. 
Igneous rocks were formed by the cooling of hot lavas 
from beneath the surface of the earth. Most uniform crystal- 
line rocks are igneous rocks, the size of the crystals being a 
good indication of whether the rocks cooled quickly or 
slowly. Large crystals indicate slow cooling; small crystals 
indicate quick cooling. Igneous rocks may also be classified 
according to chemical composition; acidic rocks being called 
granitic; basic rocks, basaltic. 
Other rocks give indications of having been formed by 
gradual deposition of material in layers over countless years. 
Under great pressures and slow chemical action the loose 
material of the layers has been cemented together. Such 
rocks are called sedimentary rocks. They contain various 
sized particles of old igneous rocks, sand, pebbles, muds, and 
the fossils of ancient forms of life, terrestrial and marine. It is 
in sedimentary rocks that fossil remains are most likely to be 
found. | 
Finally there are the metamorphic rocks, masses of rock 
which were originally either igneous or sedimentary but 
which have undergone such complete transformations under 
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