Transcript topic #1a - about hawaii

About Hawaii:
“Loveliest Fleet of Islands Anchored in
any Ocean”
Where do the islands come from?
Why do they form?
How do they form? (V1)
Hawaiian Archipelago
 Chain
of islands that strikes NW - SE
across the northern Pacific Ocean
 3000 km from nearest continent & 800 km
from nearest island
 Each island is the summit of a great
volcano that rises form sea floor
 And is part of a great undersea mountain
range.
Hawaiian Ridge & Emperor Seamounts
Hawaiian Ridge
 NW



Flat or LOW Islands - coral & agal reefs
1750 km long & 5000 m above the sea floor
Older than 6 million years
 SE


Hawaiian Islands - Kure to Nehoa
Hawaiian Islands - Kauai to Hawaii
Volcanic or HIGH islands - volcanoes
650 km long & up to 4000 m above sea level
• (what does this mean for total height?)


Younger than 6 million years
Located between Lat.19 - 21 N & Lon. 155 - 180 W
Hawaiian-Emperor chain
Main Islands & Volcanoes
Oldest to Youngest








Kauai - Kauai
Niihau - Niihau
Oahu - Waianae & Koolau
Molokai - W & E Molokai
Lanai - Lanai
Maui - W. Maui & Haleakala
Hawaii -Kohala, Mauna Kea, Hualalai, Mauna
Loa & Kilauea
Loihi
Ages of
volcanoes
in m.y.
Now, the question is
 Where
do these volcanoes come from?
 We know that most of the volcanoes &
earthquakes are located at plate margins!
 AND
 Hawaii is located in the middle of the
Pacific Ocean, far from any plate
boundary!
 So, how come volcanoes, earthquakes???
HOT SPOTS!!!
HOT SPOTS!
WHAT ARE HOT SPOTS?
Hot Spots - deep, long-lived, mostly
stationary mantle magma sources
Expressed at the surface by:
linear chain of volcanoes that
age with distance from hot spot
Over 100 identified
Used as fixed points against which
plate motion is measured
Global distribution of Hot Spots
Where do Hot Spots come from?
 Are


thought to result from mantle plumes
hot, buoyant rock rising from the deep mantle
plumes melt when they approach the surface
 Origin


of mantle plumes is not known
may come from as deep as the core-mantle
boundary
or made of recycled subducted plates??
Plate Tectonics & Hot Spots
Hot Spot Traces
 Long
chains of volcanoes with an age
progression along their length
 Occur on both oceanic and continental
lithosphere
 Form as plates move over a fixed magma
source in the mantle
 Therefore, they record plate motion
relative 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
Formation
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:
How fast does the Pacific Plate
move over the Hawaiian
Hot Spot?
L2 & L3