Lana

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Lanai and Kahoolawe
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Lanai
Slide by John Sinton
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Dirt dune, near Kanepuu
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Lanai consists of a single volcano that built up
in the shield stage and then became extinct. All
volcanic units are combined into a single unit
the Lanai volcanics NW, SW and south rift zones
are inferred from topography and dikes A
partially infilled caldera 5 km in diameter is
present in the vicinity of the Palawai basin
Slide by John Sinton
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High sea cliffs on the south side of Lanai
Slide by John Sinton
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Slide by John Sinton
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Lanai became extinct while still in the shield
stage. The Palawai basin is a remnant of the
caldera that apparently was never completely
filled in.
Slide by John Sinton
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Wind-swept coast on the north side of Lanai
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South flank of Lanai
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Early Lanai showing possible rift zones.
Coalescence of Lanai with Maui and Molokai
Toward the end of activity, rifts begin to
collapse and fluvial erosion affects the north
slope that is protected from lava inundation by
the caldera wall
Evolution and figures from Stearns (1940)
Slide by John Sinton
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Later periods are times of rising and lowering of
sea level. Much of this history is yet to be
fully determined.
Slide by John Sinton
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KAHOOLAWE
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Kahoolawe
18 x 10 km 460 m high
Kanapou Bay
Slide by John Sinton
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Stearns (1940) map showing the character of the
surface at that time.
Slide by John Sinton
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Geology of Kahoolawe by H. Stearns, based on 8
days of field work in 1939
Slide by John Sinton
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This map (Stearns, 1940) shows the distribution
of caldera-filling lavas, and post-erosional
lavas it does not separate pre- and post-caldera
lavas although the legend states that most of the
surface is covered by post-caldera lavas. It is
notable that Stearns prepared a pre-publication
map showing the distribution of pre- and
post-caldera units, but didnt publish it.
Slide by John Sinton
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Lua Kealia Lalo
Photo by Glen Bauer
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View north from Lua Makika
Photo by Glen Bauer
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This pre-publication map has been widely
distributed and eventually found its way into
circulation.
From Digital map of the Geology of the State of
HawaiI Sherrod et al., in prep
Slide by John Sinton
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Stearns noted that Kanapou Bay is bound by faults
at both ends of the bay. He interpreted these
faults as defining a caldera and separated the
thin-bedded units outside the faults and
thick-bedded units ponded against the faults into
pre-caldera and caldera-filling sequences.
Slide by John Sinton
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View of Kanapou Bay, Kahoolawe, from Maui
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Kanapou Bay, looking south (E. Maui in the
distance)
Photo by Glen Bauer
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Kanapou Bay, looking north (E. Maui in the
distance)
Photo by Glen Bauer
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The surface of Kahoolawe consists of a hard pan,
largely without vegetation.
Lying in the rain shadow of Maui, Kahoolawe was
a private sheep and cattle ranch from 1851, and a
bombing range for most of the latter part of the
20th century.
Slide by John Sinton
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Recent work (Sano et al., 2005) determining
magnetic polarity and K-Ar ages indicates that
these post-erosional units were most likely
emplaced during the Jaramillo normal polarity
chron, between 0.98 and 1.04 Ma. Thus any breaks
in activity, i.e., between the filling of Kanapou
caldera and the development of a substantial
unconformity, can be no longer than 0 - 0.2 m.y.
Kahoolawe joins Waianae and East Maui in having
experienced substantial, short-lived erosional
events, but no rejevenation.
Slide by John Sinton
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1
5
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4
3
Slide by John Sinton
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Although a substantial portion of Kahoolawe
appears to be missing, it is not clear where it
went
Slide by John Sinton
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Old pahoehoe lava flows, near Hakioawa
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An old lava tube that solidified full, and then
differential erosion removed the tube walls as
well as the rest of the flow.
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An old lava tube that solidified full, and then
differential erosion removed the tube walls as
well as the rest of the flow.
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Puu Moiwi adze quarry
This rock is very glassy, and it was an important
source of stone in olden days. The geology that
produced the glassy rock isnt clear.
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