THE LIFE AND TIMES OF A HAWAIIAN VOLCANO

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THE LIFE AND TIMES OF A HAWAIIAN VOLCANO
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THE LIFE AND TIMES OF A HAWAIIAN VOLCANO
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The production line model of Hawaiian volcano
evolution...
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Hotspots on Earth (continents seem to avoid them)
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E M P E R O R S E A M O U N T S
Hawaiian-Emperor bend (48 Ma)
Hawaii (lt1 Ma)
H A W A I I A N R I D G E
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--diagram by Chuck Blay Robert Siemers
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A "hotspot", as we know it, is an upward- moving
cylinder of solid mantle material. The material
in the center moves the fastest and therefore
finds itself out of equilibrium the most. In
turn, it melts to the greatest degree.
Volcanoes fed by this part erupt tholeiite
basalt and erupt often. The outer part moves
the slowest and only melts a little bit.
Volcanoes fed by this region erupt alkalic basalt
and erupt infrequently.
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A HOTSPOT IS PROBABLY MORE LIKE A HOT COLUMN
In reality, if the upwelling starts at the
core-mantle boundary, then a "hotspot" is more
than 10 times as tall as it is wide.
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adapted from Peterson Moore (1987)
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-melting is just getting going -alkalic basalt
composition -water pressure prevents explosive
activity -no current Hawaiian examples
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Earthquakes between 20 and 24 km depth from 1970
to 1983
(Klein et al. 1987)
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-high magma production rate continues -shallow
water depth no longer prevents explosive
activity -no current Hawaiian examples
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Surtsey (Iceland), emerging from the Atlantic in
1963
Violent interaction of erupting magma and shallow
ocean water
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Topography of Mauna Loas SW rift zone (dark
flows post-date 1778)
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Magma chamber processes, as long as there is
sufficient supply to keep the magma chamber from
solidifying
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5 km
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Mauna Kea, viewed from Hilo airport.
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Hawaii, viewed from Maui
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East Molokai, viewed from the north.
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N coast of E. Molokai
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from Moore (1964)
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from Moore et al. (1989)
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The boulders are sorted by age Different sea
levels? Multiple tsunami?
1 m
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-volcano moves off hotspot -erosion becomes
dominant geological process -extensive reefs
develop -Kohala
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Mauna Keas lower NE flank
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peninsula formed from lava that flowed down a
large stream valley
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Waipio and Waimanu valleys, Kohala volcano
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Extensive reef development on the S coast of
East Molokai
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-source of magma (and explanation) not
clear -extremely low degrees of partial melting
(very alkalic compositions) -very small overall
volume of volcano -Koolau, Kauai
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Koko Rift, SE end of Koolau Volcano, Oahu
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Kalaupapa peninsula, banked against the giant
avalanche scarp and large erosional valleys.
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-erosion and subsidence continue -reef-building
keeps pace with subsidence -NW Hawaiian islands
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Northwest Hawaiian Islands
Holoikauaua (Pearl Hermes Reef)
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-subsidence maybe continues -reef-building cannot
keep up (water too cold) -Emperor Seamounts
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E M P E R O R S E A M O U N T S
H A W A I I A N R I D G E
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Maps produced by Dave Sherrod, USGS
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PAU