Over 100 volcanoes in a volcanic island arc system

Big Island

Meiji(3000 m deep)

Hawaiian IslandsHawaiian Islands

Hawaii

Oahu

Kauai

Lanai Maui

Molokai

Niihau

Bathymetric Profile of Hawaiian Emperor Chain

Hawaii

(youngest)MauiOahuKauai

(oldest)Pacific Plate

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 farther they travel beyond the hotspot.

Age of Hawaiian Islands

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

Moves in a northwesterly direction

WE’VE GOT HOT SPOTS ALL OVER THE PLACEOther 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

Barrier Reef- separated from land by a lagoon

Fringing Reef- boarders coastline closely

Island subsides

Atoll- coral ring with central lagoon

lagoon is a shallow area with a sandy floor, patch reefs, and patches of seagrass

Darwin’s Theory of Coral Atoll Formation: Subsidence Theory

Fringing Reef- Tahiti

Fringing ReefFringing Reef

Reef FlatReef Flat

Reef FrontReef Front

ShorelineShoreline

Barrier Reef ProfileBarrier Reef Profile

reefslope

reeffront

outerreef flatlagoonpatch

reef

islandinnerreef flat

Australia- Great Barrier Reef

                                                            

Kaneohe Bay

Barrier ReefBarrier Reef

Fringing ReefFringing Reef Patch ReefPatch Reef

Reef Flat of a barrier reefReef Flat of a Barrier ReefReef Flat of a Barrier Reef

Reef FlatReef Flat

Coral Island(Cay or Motu)Coral Island

(Cay or Motu)

Reef FrontReef Front

LagoonLagoon

Open OceanOpen Ocean

Cross Section of an Atoll

Cross Section of an Atoll

Atoll

Belize- Blue Hole

Kure Atoll (28° 25' N - 178° 20' W)Midway Atoll

Pearl & Hermes Atoll

Inquiry

1. The oldest seamount in the Hawaiian Emperor Chain is _____?

2. What direction are our islands moving?

3. What seamount will be the newest Hawaiian Island?

4. Key features of a barrier reef are_____?

5. When an atoll subsides it often forms a _____?