023 hawaiian island geology

Meiji
(3000 m deep)

Over 100
volcanoes in a
volcanic island
arc system

Big Island


Hawaiian Islands

Niihau

Kauai
Oahu

Molokai
Lanai

Maui

Hawaii


Bathymetric Profile of Hawaiian Emperor Chain


J. Tuzo Wilson (1963), a Canadian geophysicist ,came up

the "hotspot" theory.
volcanoes of the Hawaiian
chain should get
progressively older and
become more eroded the
e
t
a
l
i
P
a
farther they travel beyond
c
u
i
f
a
)
i
t
K
es
d
l
Pa c
the hotspot.
o
(
u

h
Oa
ui waii st)
a
M
Haounge
(y


Age of Hawaiian Islands


Moves in a northwesterly direction

Much of the Hawaiian island arc is
underwater and extends toward Midway


WE’VE GOT HOT SPOTS ALL OVER THE
PLACE
Other examples of hot spots
include:
Cape Verde (off the coast of Senegal), Galapagos Islands
(off the coast of Equator), Society Islands (French
Polynesia), Tristan da Cunha (southern Atlantic),
Yellowstone, Ethiopia Plateau, Lord How (near Sydney),
Iceland, and many more.


Older islands erode and subside

Aging islands and coral:
• Drilling and removing core sample
• C14 dating




Darwin’s Theory of Coral Atoll Formation: Subsidence Theory

Fringing Reef- boarders coastline closely

Island subsides

Barrier Reef- separated from
land by a lagoon

Atoll- coral ring with central lagoon
lagoon is a shallow area with a sandy
floor, patch reefs, and patches of
seagrass


Fringing Reef- Tahiti


Shoreline
Fringing
Reef

Reef Flat

Reef Front


Barrier Reef Profile

patch
reef

lagoon

inner
reef flat

island

outer
reef flat

reef
front

reef
slope


Australia- Great Barrier Reef

Kaneohe Bay
Barrier Reef

Fringing Reef

Patch Reef


Lagoon

ReefFlat
Flatof
ofaaBarrier
barrier
reef
Reef
Reef
Coral
Island
(Cay or Motu)

Reef Flat
Reef Front

Open Ocean


Cross Section
of an Atoll

Belize- Blue Hole

Atoll


Midway Atoll

Kure Atoll (28° 25' N - 178° 20' W)

Pearl & Hermes Atoll