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