June 21

Exceptional Atoll

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An ATOLL is a very unique geographic  feature.  It looks like an island with a large central water-filled area.  

It is a ring-shaped reef, island, or chain of islands formed of coral.

An atoll is often formed from a volcano that is submerged in the water.   These old volcanos are extinct, and are often worn down and filled in to form a bowl-like depression.  The upper ring-like surface of them is covered in coral.  This is a photo of the Addu Atoll, in the Maldives, seen from space.

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Sometimes an atoll looks like a ring, and others appear to be a broken ring.   The volcanic crater rises a little above water or is not very deep.  Coral grows along the crater of the volcano and this forms a reef.   This coral reef that surrounds this water-filled lagoon.

(Vocabulary word!  A LAGOON is shallow body of water separated from a larger body of water by coral reefs or barrier islands.)

 

IN THE TROPICS

Atolls are only found in the tropics and subtropics waters.  Why?  The kinds of coral that build reef like structures can grown only in warm tropical and subtropical waters.

The shape is often circle or ring-like, but atolls form in different shapes too, like the one shown below, the atoll named Atafu, part of the country of Tokelau.Tokelau is an island country and also a territory of New Zealand. Located in the South Pacific Ocean, Tokelau consists of three tropical coral atolls named Atafu, Nukunonu and Fakaofo. There is also a small Swains Island which is governed as part of American Samoa.  Together, these small pieces of coral and land only measure a total of 4 sq miles. Approximately 1,400 people live in this small tropical area.

This photo shows the atoll named Atafu, part of the country of  Tokelau

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THE MALDIVES

The Maldives Archipelago are a chain of islands in the Indian Ocean.  There are 1,192 islands total, but people live on only 192 of them.  The Maldives are unique among islands.  The island form are the smallest country in ASIA, both in size and in population.  One of the most unusual things about the Maldives is that there are many atolls — 26 total.  

The Maldives are actually part of an underwater — or submarine–  mountain range that emerges out of the ocean.  In 2004, the great Indian Ocean Earthquake caused much destruction on these low lying islands.  Six islands were destroyed by a tsunami.  Rising sea levels are extremely dangerous for these islands that are so low in elevation.  Learn more about this fascinating island/atoll country– its wildlife, the challenges faced by rising seas, and more– in our CartoCraze! Expanded Map Workshops.  These digital files offer more information about many other islands as well!

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This photo shows a populated island in the Maldives, as well as nearby atolls.

 

A SPECIAL ATOLL INHABITANT, in an exceptional atoll!

Atoll islands are very low lying, and do not have peaks.   An atoll often has very little land in comparison to the total area including lagoon water and coral reefs. Some atolls have areas where small communities live, others are populated by wildlife only.  Many fish and aquatic creatures lives in the coral reefs.

The Laysan Albatross “Wisdom” is Wisdom is the oldest confirmed wild bird in the world!  She also has the distinction of being the oldest banded bird in the world.  She is at least 65 years old and is the oldest known wild bird in the United States.  Here she is shown with her newly hatched chick, at Midway Atoll National Wildlife Refuge in March 2011.  Since then she has reared other chicks as she lives her life in the atoll.

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Midway Atoll, shown below, is part of a chain of volcanic islands, atolls, and seamounts, and is part of the Hawaii-Emperor chain in the Pacific Ocean.  It has a ring-shaped barrier reef and several sand islets. Two areas of land, Sand Island and Eastern Island, are home to millions of seabirds, including “Wisdom”!

Midway_Atoll_aerial_photo_2008

 

 


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