Formation of the Hawaiian Islands
Volcanoes, Magma, and Hot Spots
Topics
• Hawai’i
• Ring of Fire
• Hot Spots
• Decompression Melting
• The Hawai’i Hot Spot
Topics
• Hawai’i
• Ring of Fire
• Hot Spots
• Decompression Melting
• The Hawai’i Hot Spot
The Hawai’i Hot Spot
Volcanoes in the Sea
Volcanoes in Hawaii form from a mantle
plume
Volcanoes in Hawaii form from a mantle
plume
Hot, solid rocks rise to a depth of
approximately 60 km, where melting
occurs
Volcanoes in Hawaii form from a mantle
plume
Hot, solid rocks rise to a depth of
approximately 60 km, where melting
occurs
The less dense magma rises to form a
volcano
Currently the Big Island of Hawai’i overlies
the Hawai’i Hot Spot
Hawai’i Hot Spot
Hawai’i Hot Spot
Big Island of Hawai’i
Hot Spot Dimensions
80 - 100 km wide as it rises
Hot spot head mushrooms at the
base of the lithosphere to 100 200 km wide
Mushrooming head of
the mantle plume
60 km deep
Mushrooming head of
the mantle plume
60 km deep
m
k
0
0
2
0
0
1
Mushrooming head of
the mantle plume
Hawai’i Archipelago
Hawai’i Archipelago
Only one Hawai’i hot spot
Hawai’i Archipelago
Only one Hawai’i hot spot
Currently under the Big Island
Hawai’i Archipelago
Only one Hawai’i hot spot
Currently under the Big Island
Why a chain of islands?
Hawai’i Archipelago
Only one Hawai’i hot spot
Currently under the Big Island
Why a chain of islands?
What is moving?
Hawai’i Archipelago
Hawai’i Archipelago
Hawai’i Hot Spot is relatively stationary
Hawai’i Archipelago
Hawai’i Hot Spot is relatively stationary
All of the Hawaiian island were formed
approximately where the Big Island is
Hawai’i Archipelago
Hawai’i Hot Spot is relatively stationary
All of the Hawaiian island were formed
approximately where the Big Island is
The Pacific lithospheric plate is moving
over the top of the hot spot
Sea-Floor Spreading
Sea-Floor Spreading
Pacific lithospheric plate spreads over the
Hawai’i Hot Spot
Sea-Floor Spreading
Volcano forms above hot spot, then is
carried away by sea floor spreading
Sea-Floor Spreading
A new volcano subsequently forms over
the hot spot as a chain of islands develops
Plate Spreads Northwest
Plate Spreads Northwest
NW
Question
Why discrete islands?
Question
Why discrete islands?
Possible Mechanisms
Masses of magma rise periodically
Temperature of the mantle plume varies,
to the degree of melting varies
Plumbing system maintains itself for a
particular length of time
Do the characteristics of the Hawaiian
Archipelago support this hypothesis?
Changing Characteristics
Changing Characteristics
With increasing distance from the hot
spot, the islands become progressively
1. older
2. more eroding
and they are sinking
Hawai’i
O’ahu
Kaua’i
Islands are sinking
Most of the northwest
islands are atolls
Northwest Hawaiian Islands