Transcript Island Arcs

QUICK QUIZ
1.Give an example of an Continental Island
2.Name one of the three parts of a Ridge.
3.An area of Subduction will form what type
of structure in the ocean?
4.What is a flat topped Seamount called?
5.Long Island and England are what type of
Islands?
Island Formation
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How do Islands form?
Island Arcs- Philippines
Hot spots---The Hawaiian Islands
What does Darwin have to do with this?
Atolls and Coral reefs
1. Continental Islands = UK, New Zealand.
2. Island arcs – Philippine & Aleutian Islands
3. Volcanic Islandsa. volcanic = Iceland, Hawaii, Azores, etc.
(1) along mid-ocean ridges, or
(2) mid-basin “hot spots”.
b. coral - atolls
(1) formed in warm, clear,
tropical oceanic waters.
(2) have volcanic bases.
Continental Islands
• Large chuck of land
breaks off of a
continental land
mass.
• Ireland, England were
originally part of the
European continent
(fig 2.14 p 31)
• New Zealand was
part of Australia
Which Island can the Mid Atlantic
Ridge be seen on land.
Ireland
Iceland
Finland
Greenland
It cannot be seen
on land
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The three part of a ridge are the
1. Flank, Ridge and
slope
2. Flank, Ridge
Valley and Base
3. Flank, Rift Valley
and Crest
4. Slope, Break and
Shelf
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An example of Island Arcs created
through subduction are
Iceland
Hawaiian Islands
Manhattan Island
The Islands of
Japan
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29%
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The most common geological
structure in the ocean is
Abyssal Plains
Seamounts
Guyots
Abyssal Hills
38%
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A
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B. Island Arcs
1. arc-shaped chains of islands (Marianas,
Aleutians)
2. usually on continent side of trenches.
3. made by active volcanoes - explosive type.
4. marginal basins
a. between arcs and continents
b. serve to trap sediment and block it
from the deep sea.
Aleutian Islands
Island Arc Formation
Hot Spots-Volcanic Islands
• A volcanic “plume” at a fixed spot in the mantle
pushes through the crust creating a volcano.
• The volcano builds becoming a seamount which
crests the ocean surface.
• The crust moves over the spot and the process
is repeated.
• This is why you will get Island Chains such as
the Hawaiian Islands
Hot Spot Formation
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Volcanic
Features
The Island Of
Hawaii
Coral Reefs
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Tropical waters only (temperature matters)
20 – 30 degrees C
Form in shallow water next to island
As island erodes, reef remains
Can only live in Photic zone- If the Island (Atoll)
sinks below the photic zone the coral will die.
• Photic Zone is the upper layer of water where
light can penetrate.
•Largest reef –Great Barrier Reef covers 80,000 square miles
Charles Darwin
Darwin
• In his voyage around the world in the
1830’s Darwin formulated his theory on
reef and atoll formation
• This theory is still considered valid and is
used to this day
Life of a coral reef
(as per Darwin)
Fringing reef
Barrier reef
Atoll