Island of Lana

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• Island of Lanai
• Formed of a single shield volcano, Palawa
  caldera on the Maui Nui
• The Lanai volcano reached the subaerial sheild
  stage, has a single volcanic rock member
• Lanai Member, tholeiitic basalt, 1.46 to 0.78 Ma
• pahoehoe and aa, and and spatter cones on the
  rift zones
• caldera partly filled by lava, but is still
  visible
• three rift zones
• grabens along rift zones
• This volcano also has has marine deposits,
  evidence for higher stands of the sea

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Island of Lanai
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Pacific Ocean
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Pacific Ocean
Lanai Volcano Palawa caldera Rift zones
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Lanai slumped into sea on southwest sea cliff
exposing faults
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Lanai, volcanic ridge line is the old caldera rim
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Island of Kahoolawe
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Island of Kahoolawe

• Formed of a single shield volcano
• Shield Stage, Lower Member (age unknown)
• caldera is present but filled in, 5 km diameter
• typical shield lavas, tholeiitic basalt
• later shield-stage lavas have high silica
  (similar to Koolau)
• source rock for adzes found all over Hawaii
• Postshield Stage, Upper Member, 1.0 Ma
• small extent, include top part of caldera filling
  lavas
• hawaiite
• Rejuvenation Stage Vents?
• Youngest vents cut alluvium, but are tholeiitic
  (!) found at top of sea cliff
• Water problems--shallow wells yield brackish
  water
• in rain shadow of Maui also a low island
• little vegetation--overgrazed (had been used as a
  ranch)
• soil erosion by wind
• Eastern part of volcano is missing--landslide?
• No debris, but eruptions from SW rift of East
  Maui may bury deposits

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Kaholawee Volcano Caldera and rift zones
Pacific Ocean
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Island of Kahoolawe
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Pacific Ocean
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Sea arches and sea cliffs exposing
caldera-filling lavas
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