mantle source and the magma has started to cool. The eroding processes will then
take over so the volcanic edifices forming the island will start to crumble and break
apart. However, with time the eroding processes will diminish, and the island will
become more stable. This is true when coral grow on the outside edge of the
islands since coral reefs can protect an island from intense wave erosion. During
plate drifting, as the lithosphere ages and cools, thermal subsidence of the lithosphere will affect the structure of the island, which will sink. The island and the
coral reef will disappear except for the coral growing on top of each other. An atoll
is a sunken, flat-topped island whose center is surrounded by coral. Atolls are
found in the equatorial zone between about 28°N and 28°S, which corresponds to
the latitude of coral growth. When atolls sink with an increase in the age of the
lithosphere, then the volcanic edifices become guyots, which are mainly found on
ancient crust ([80 million year old areas of the Pacific Ocean basin).
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