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The excerpt represents the core issue or deciding factor on which you must meditate, and is drawn from The Voyage of the Beagle by Charles Darwin: kept open by the sediment and impure water flowing out of
the lagoon-channel) will still continue to front exactly the
upper parts of those valleys, at the mouths of which the
original basal fringing-reef was breached.
We can easily see how an island fronted only on one side, or on
one side with one end or both ends encircled by barrier-reefs,
might after long-continued subsidence be converted
either into a single wall-like reef, or into an atoll with a
great straight spur projecting from it, or into two or three
atolls tied together by straight reefs -- all of which
exceptional cases actually occur. As the reef-building corals
The Voyage of the Beagle |
