Post on 25-Dec-2015
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
• 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 Islands3. Volcanic Islands-
a. 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.
Irel
and
Icel
and
Fin
land
Gre
enla
nd
It c
annot b
e se
en o
n...
14%
71%
14%
0%0%
1. Ireland
2. Iceland
3. Finland
4. Greenland
5. It cannot be seen on land
The three part of a ridge are the
Fla
nk, R
idge
and s
lope
Fla
nk, R
idge
Valle
y a.
.
Fla
nk, R
ift V
alle
y an
d...
Slo
pe, B
reak
and
Shel
f
0% 0%
100%
0%
1. Flank, Ridge and slope
2. Flank, Ridge Valley and Base
3. Flank, Rift Valley and Crest
4. Slope, Break and Shelf
An example of Island Arcs created through subduction are
Icel
and
Haw
aiia
n Isla
nds
Man
hatta
n Is
land
The
Isla
nds o
f Jap
an
14%
29%
14%
43%1. Iceland
2. Hawaiian Islands
3. Manhattan Island
4. The Islands of Japan
The most common geological structure in the ocean is
Abys
sal P
lain
s
Sea
mount
s
Guyo
ts
Abys
sal H
ills
25%
38%
13%
25%
1. Abyssal Plains
2. Seamounts
3. Guyots
4. Abyssal Hills
B. Island Arcs1. 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 continentsb. serve to trap sediment and block itfrom the deep sea.
Aleutian Islands
Island Arc F
ormation
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
•
Volcanic Features
The Island Of
Hawaii
Coral Reefs
• 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