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By studying these
coral islands scientists were able arrive at the possible
weather conditions prevalent centuries ago. Based on the fact
that unfavorable conditions such as cold periods result in
darker corals, marine biologists in Florida have
identified the years when there were cold fronts, storms and
radioactive fallout from nuclear weapon tests. For this,
scientists studied layers in ten feet cores or coral in
Florida. |
A Coral Reef |
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Volcanic islands
Islands like the Hawaii and the Surtsey (off Iceland) are some
examples of volcanic islands. Eruption of volcanoes from weak points
in the Earth’s crust have created such islands. When there is a
volcanic explosion, molten rock and ash are forced up from the
seabed. Once out, they form a cone shaped island. These islands are
surrounded by vapor from the vent of the volcano. Gradually, sea
waves eat into the island and wear down the cliffs, forming a
platform on which coral grows. In due course, the main vent cools,
however a lesser one remains active, which results in crumbling
rocks, that form soil. Plants and animals slowly start inhabiting
these cooled platforms. However, as a lesser vent remains active,
erosion continues to occur now and then, resulting in offshore
stacks. Over a period of time the island sinks, with only a tip of
the original cone shaped island on the ocean’s surface.
Krakatoa is an Indonesian island volcano, which erupted in 1883. The
ash and pumice erupted wiped out all life on the island. However,
the island was re-colonized at an amazing speed. It is said that
exactly nine months later, a solitary spider was seen spinning a
web. Three years later, naturalists claimed that they had located
eleven species of ferns and fifteen varieties of flowering plants on
the island.
Forty years later, Krakatoa was covered with lush forest and was
home to one thousand two hundred species of animals, including
pythons and bats.
The loneliest island in the world is said to be a volcanic island
called Tristan da Cunha, near Britain. The nearest land is two
thousand and twenty kilometers away from Tristan.
After a volcanic eruption in 1961, the inhabitants were moved to
Britain. However, many returned to the island a few years later,
unable to cope with the hectic pace of urban life.
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