islands
The islands are ground
extents surrounded by water of any
share.
One finds islands not
far from the continental coasts, or on the contrary in the beautiful medium of
the seas and the oceans. Some are insulated, others are joined
together in a group of other islands (it
is what one calls an archipelago).
Certain islands is of volcanic
origin (they were created by
volcanic eruptions), others of coral origin
(they are formed by coral reefs), as it is the case of the
atolls. Some are due to the erosion of marine rocks. Others, like
Madagascar or Corsica, originate in the movements of the continental plates (plate tectonics): in fact pieces of the
earth's crust are separate continents. Lastly, certain islands are the result
of a
rise in the sea level: only the reliefs emergent and are isolated in the
mediums from water.
Isolated from the
continents, the islands often shelter many animal and vegetable species
"original", that one does not find nowhere elsewhere in the world
(one speaks about endemic species).
In Madagascar for example, 85 % of the plants and 90 % of the animals are
endemic.
TO GO FURTHER
? seas and oceans
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