2. ISLANDS
•An island isa piece of land that issurrounded
by water.
•Water isall around an island.
•I
slands are smaller than continents.
•T
he word island comes from English igland means
“portion of land surrounded by water”
3. An or isle is a tract of land that is completely surrounded by water, above
high tide, and isolated from other significant landmasses, yet is not large enough
to be called a continent.
Islands may be found in , seas, lakes, or rivers.
The world's ten largest islands, in descending order of size are ,
New Guinea, Borneo, Madagascar, Baffin Island, Sumatra, Honshu, Great
Britain, Victoria Island and Ellesmere Island.
4. Very small islands such as emergent land features on atolls are
called islets.
Atoll is an island formed from a coral reef that has grown
on an eroded and submerged volcanic island.
5. A KEY OR CAY IS ANOTHER NAME FOR A SMALL ISLAND OR ISLET.
An island in a or lake may be called an eyot/ holm.
The Isle of Sheppey is an island off the northern coast of Kent, England in the Thames river
6. ISLANDS CLOSELY GROUPED TOGETHER ARE CALLED AN ARCHIPELAGO.
is an archipelago of 21 islands and islets in
the Atlantic Ocean, 354 km (220 mi) offshore from the Brazilian
coast.
7. IT IS GENERALL
YACCEPTED THA
T THEREARE TWO
TYPES OF ISLANDS
1.OCEANIC ISLANDS
2.CONTINENTAL ISLANDS
Oceanic Islands are those that do not sit on continental shelves but
rise to the surface from the floors of the ocean basins. They are
volcanic in origin. Lava accumulates to such thickness that it finally
protrudes above the ocean surface.
8. OCEANIC ISLANDS
•Oceanic Islands are not part of continental shelf areas,
they are not, and have never been, connected to a
continental land mass
•Oceanic islands originate in volcanic action typically
associated with the movement of the lithospheric
plates. Most typically these are volcanic islands.
•Mariana I
slands in the western Pacific Ocean isan
example.
9. There are two types of islands
Oceanic
Islands Volcanic
Islands
Coral Islands
10. VOLCANIC ISLANDS
•Oceanic islands are ones that do not sit on continental
shelves. The vast majority are volcanic in origin.
•The few oceanic islands that are not volcanic are tectonic
in origin and arise where plate movements have lifted up the
deep ocean floor to above the surface. Example of this
include Saint Peter in the Atlantic Ocean.
11. VOLCANIC ISLANDS
•One type of volcanic oceanic island is found
in a volcanic island arc. e.g. Mariana Islands
in the Pacific Ocean.
•Another type of volcanic oceanic island
occurs where an oceanic rift. e.g. Iceland in
the Atlantic ocean.
•A third type of volcanic oceanic island is
formed over volcanic hotspots. e.g. Hawaiian
Islands in Pacific ocean
12. The islands of Hawaii are volcanic islands. Volcanic Islands in French Polynesia
13. CORAL ISLANDS
• The islands are formed by calcium
carbonate (limestone) in shallow tropical sea
by living organisms over thousands of years.
• The most important organisms that
precipitate CaCO3 from sea water to form
reef are corals called hermatypic corals and
coralline algae.
14. CORAL REEF TYPES
• Fringing reef: close to a landmasswith either no
lagoon or a narrow lagoon between reef and shore.
• Atolls:that encircle a lagoon but not an island.
• Barrier reef: runs roughly parallel to shore and has a
wider and deeper lagoon than does a fringing reef.
• Patch or Bank reefs: occur some distance back from
the barrier reef.
15.
16.
17. CONTINENTAL SHELF:
THE CONTINENTAL SHELF IS AN UNDERSEA EXTENSION
OF A CONTINENT WHICH CAN STRETCH FOR MANY
MILES OUT TO SEA IN SOME CASES.
18. Contine
A special type of continental island is the microcontinental island, which
results when a continent is . Examples are and Socotra off
Africa; New Zealand; New Caledonia; the Kerguelen Islands; and some of the
Seychelles.
19. ANOTHER SUBTYPE ISAN ISLAND OR BAR FORMED BY DEPOSITION OF
WHEREAW
A
TER CURRENT LOSES SOME OF ITS CARRYING
CAPACITY
.AN EXAMPLE IS , WHICHARE
ACCUMULATIONS OF SAND DEPOSITED BY SEA CURRENTS ON THE
CONTINENTALSHELF.
There are some schools of thought that break continental islands into further
categorization, those of
Recent Continental Islands
Ancient Continental Islands.
:
The separating sea between the islands and the mainland is less than fathoms deep
and they have been repeatedly connected and disconnected to the mainland.
Examples: Britain, Japan, Tasmania, Sumatra,Java, Borneo,Taiwan and Sri Lanka.
20. THEY WERE CONNECTED TO THE MAINLAND IN THE
ANCIENT PAST, SOMETIME IN THE MESOZOIC PERIOD
BUT HAVE NEVER HAD ANY CONNECTION WITH THE
MAINLAND EVER SINCE.
EXAMPLES: MADAGASCAR AND NEW ZEALAND.
22. There are a number of ways that these islands can come into existence.
1.Often, continental islands are created by a where only the highest
points of the land remain above water. This is exactly how much of present day New
York City was created - after all, Manhattan is an island.
2.Similarly, a continental island may be formed when water breaks or
, separating it from the mainland. Malaysia is renowned for its stunning
peninsular islands.
Microcontinental islands are formed when a portion of the landmass
; island nations such as Madagascar and Cuba are good examples.
