about hawaii: “loveliest fleet of islands anchored in any ocean” where do the islands come from?...

About Hawaii:About Hawaii:““Loveliest Fleet of Islands Anchored in Loveliest Fleet of Islands Anchored in

any Ocean”any Ocean”

Where do the islands come from?Where do the islands come from?

Why do they form? Why do they form?

How do they form? How do they form? (V1)(V1)

Hawaiian ArchipelagoHawaiian Archipelago

Chain of islands that strikes NW - SE Chain of islands that strikes NW - SE across the northern Pacific Oceanacross the northern Pacific Ocean

3000 km from nearest continent & 800 km 3000 km from nearest continent & 800 km from nearest islandfrom nearest island

Each island is the summit of a great Each island is the summit of a great volcano that rises form sea floorvolcano that rises form sea floor

And is part of a great undersea mountain And is part of a great undersea mountain range.range.

Hawaiian Ridge & Emperor SeamountsHawaiian Ridge & Emperor Seamounts

Hawaiian RidgeHawaiian Ridge

NW Hawaiian IslandsNW Hawaiian Islands - Kure to Nehoa - Kure to Nehoa Flat or Flat or LOWLOW Islands - coral & agal reefs Islands - coral & agal reefs 1750 km long & 5000 m above the sea floor1750 km long & 5000 m above the sea floor Older than 6 million years Older than 6 million years

SE Hawaiian IslandsSE Hawaiian Islands - Kauai to Hawaii - Kauai to Hawaii Volcanic or Volcanic or HIGHHIGH islands - volcanoes islands - volcanoes 650 km long & up to 4000 m above sea level650 km long & up to 4000 m above sea level

• (what does this mean for total height?)(what does this mean for total height?) Younger than 6 million yearsYounger than 6 million years Located between Lat.19 - 21 N & Lon. 155 - 180 WLocated between Lat.19 - 21 N & Lon. 155 - 180 W

Hawaiian-Emperor chain

Main Islands & VolcanoesMain Islands & VolcanoesOldest to YoungestOldest to Youngest

Kauai - KauaiKauai - Kauai Niihau - NiihauNiihau - Niihau Oahu - Waianae & KoolauOahu - Waianae & Koolau Molokai - W & E MolokaiMolokai - W & E Molokai Lanai - LanaiLanai - Lanai Maui - W. Maui & HaleakalaMaui - W. Maui & Haleakala Hawaii -Kohala, Mauna Kea, Hualalai, Mauna Hawaii -Kohala, Mauna Kea, Hualalai, Mauna

Loa & KilaueaLoa & Kilauea LoihiLoihi

Ages of volcanoes

in m.y.

Now, the question isNow, the question is

Where do these volcanoes come from?Where do these volcanoes come from? We know that most of the volcanoes & We know that most of the volcanoes &

earthquakes are located at plate margins!earthquakes are located at plate margins! ANDAND Hawaii is located in the middle of the Hawaii is located in the middle of the

Pacific Ocean, far from any plate Pacific Ocean, far from any plate boundary!boundary!

So, how come volcanoes, earthquakes???So, how come volcanoes, earthquakes???

HOT SPOTS!!!HOT SPOTS!!!

HOT SPOTS!HOT SPOTS! WHAT ARE HOT SPOTS?WHAT ARE HOT SPOTS?

Hot Spots - deep, long-lived, mostly stationary mantle magma sourcesExpressed at the surface by:

linear chain of volcanoes thatage with distance from hot spot

Over 100 identified Used as fixed points against which plate motion is measured

Global distribution of Hot SpotsGlobal distribution of Hot Spots

Where do Hot Spots come from?Where do Hot Spots come from?

Are thought to result from Are thought to result from mantle plumesmantle plumes hot, buoyant rock rising from the deep mantlehot, buoyant rock rising from the deep mantle plumes melt when they approach the surfaceplumes melt when they approach the surface

Origin of mantle plumes is not knownOrigin of mantle plumes is not known may come from as deep as the core-mantle may come from as deep as the core-mantle

boundaryboundary or made of recycled subducted plates??or made of recycled subducted plates??

Plate Tectonics & Hot SpotsPlate Tectonics & Hot Spots

Hot Spot TracesHot Spot Traces

Long chains of volcanoes with an age Long chains of volcanoes with an age progression along their lengthprogression along their length

Occur on both oceanic and continental Occur on both oceanic and continental lithospherelithosphere

Form as plates move over a fixed magma Form as plates move over a fixed magma source in the mantlesource in the mantle

Therefore, Therefore, theythey record plate motion record plate motion relative to the mantlerelative to the mantle

Hawaiian-Emperor chain

Location of the various islands over the hot spot

(red circle) at different

times

A Quick Review of Island A Quick Review of Island FormationFormation

Islands form over a “hot spot” in the mantle then move away riding the Pacific Plate

Results in a chain of islands with an age progression along its length

{Responsible for different magma types in different life stages, or whether there is any magma available at all} - when magma supply is low, erosion dominates shaping the landscape

Homework #1:Homework #1:How fast does the Pacific PlateHow fast does the Pacific Plate

move over the Hawaiianmove over the HawaiianHot Spot?Hot Spot?

L2 & L3L2 & L3