1. Island of Kaua‘i
Kaua‘i, one of the older islands in the chain, is also the most complex structurally.
Generally thought of as a single-volcano island, some isotopic data challenge that interpretation. Consequently, Kaua‘i provides many opportunities to substantially broaden our understanding of how ocean-island volcanoes develop.
Kaua‘i is the fourth largest island.

2. Geology of Kaua‘i
Kaua’i consists of perhaps a single shield volcano formed 5 million years ago. Wai‘ale‘ale Volcano.
Like the Ko’olau Volcano on O‘ahu, only has shield stage and rejuvenation stage without the post-caldera alkalic cap
Lacks well-defined rift zones like O‘ahu volcanoes
This volcano has experienced significant faulting and has the largest known caldera of any Hawaiian volcano
This volcano has also passed through the erosion and coral reef growing stages
Erosion also affected by faulting: Waimea Canyon

3. Kaui's Volcanoes Revealed
Prominent terraces (shown in orange and yellow)
illustrate the larger size of the islands in the past.
in particular, are mere vestiges of their former extent

4. 160°W
North Kaua‘i
Slide
22°N
Kaua‘i
Ka‘ula
Ni‘ihau
South Kaua‘i
Slide
Oahu
Deep

5. Kaua‘i Volcano, Shield Stage
Shield-stage rocks are called the Waimea Canyon Volcanic Series
Na Pali Member (5.10 to 4.30 Ma)
shield-forming rocks outside of the caldera
thin, inclined flows
tholeiitic basalt
Olokele and Makaweli Members ( Ma)
fill the caldera and the Makaweli graben (normal falut-bounded valley), respectively
thick, flat-lying flows
tholeiitic basalt, alkalic basalt, and hawaiite
Haupu Member (unknown age)
lavas filling a small caldera on the southeastern flank of the volcano

6. Shield building
Stage
Rejuvenated Stage

8. Kaua‘i Volcano, Rejuvenation Stage
Called the Koloa Volcanic Series
Age: 2.3 to 1.0 Ma
~40 vents, spatter and cinder cones, and a tuff cone
Koloa lavas cover about half of the surface of the eastern part of the island
floor the Lihue Basin
Mt. Kilohana and flows
Interbedded with the Koloa Volcanic Series is the Palikea Formation, consisting of conglomerates and breccias, coarse sedimentary rocks produced by mass wasting-style erosion

9. Rejuvenated Stage Volcanic Eruptions on Kaui

10. Kaua‘i Volcano, Rejuvenation Stage
Called the Koloa Volcanic Series
Age: 2.3 to 1.0 Ma
~40 vents, spatter and cinder cones, and a tuff cone
Koloa lavas cover about half of the surface of the eastern part of the island
floor the Lihue Basin
Interbedded with the Koloa Volcanic Series is the Palikea Formation, consisting of conglomerates and breccias, coarse sedimentary rocks produced by mass wasting-style erosion

12. Sedimentary Rocks
Extensive deposits of colluvium (mass wasting deposits) and alluvium (stream erosion deposits)
Cemented sand dunes and beach rock
Sediments can form coastal plains

13. Two Shield Volcanoes or one
Two Shield Volcanoes or one?: The two-volcano hypothesis remains a topic worthy of pursuit.
An alternative interpretation has been suggested on the basis of strontium isotopic analyses from late-shield strata of the Waimea Canyon Basalt on the west and east sides of the island, which differ sufficiently to suggest that two magma-supply systems were erupting during the growth of Kaua‘i.
An additional rationale offered in support of a two-volcano hypothesis is the possibility of numerous rift zones radiating outward in as many as five directions (Holcomb et al, 1997). A two-volcano, five-zone rift system was depicted in a simplified map figure by Clague (1996).

14. Island of Ni‘ihau
Ni‘ihau, covering 187 km2 , is the westernmost of the Hawaiian Islands.
Ni‘ihau is the eroded remnant of a single shield volcano.
It is third smallest of the major Hawaiian islands, larger only than Kaho‘olawe and Lāna‘i.
Its land is held privately, and access is controlled; consequently it is one of the least visited and least studied of the Hawaiian islands.
Offshore, a fringing wave-cut shelf extends out 5–10 km, beyond which the slopes plunge steeply to abyssal depth.

15. Geology of Island of Ni‘ihau
Lies off of main trend of Hawaiian Islands, a “cross trend”
Topographically it comprises a central highland built almost entirely of shield-stage pāhoehoe lava flows (Pānī‘au Basalt).
A deeply eroded remnant of a shield volcano fringed by a platform composed of rejuvenation stage volcanic rocks
Ni‘ihau’s rejuvenated-stage lava - A late vent, Ka‘eo, stands about 60 m above the surrounding surface. Possibly a product of postshield-stage activity.
More than 23 percent of this platform’s area is mantled by alluvium and dune deposits with well-developed calcareous dune deposits.

16. Ni‘ihau Volcanic Rocks
Shield Stage
Paniau Volcanic Series, 5.5 to 4.8 Ma
tholeiitic and olivine-rich basalts, dikes and lavas
evolving towards alkalic postsheild stage?
caldera and summit are gone, only a rift zone remains
erosion? faulting?
Rejuvenation Stage
Ki‘eki‘e Volcanic Series, 2.2 to -0.3 Ma
9 vents, including Lehua Island
all are dry eruptions except for 2 tuff cones
produced lavas that cover a wave-cut terrace
alkalic olivine basalt, not as low in silica as rejuvenation stages on other islands

17. Geology of Island of Ni‘ihau – Rift Zones

18. Island of Lehua
Lehua island is a tiny Ki‘eki‘e Basalt tuff cone, only 1.1 km2 in area, that lies 1 km north of Ni‘ihau .
Undated, it is fairly youthful, to judge from its landform. Ash from its eruptions carried across much of Ni‘ihau, forming weakly consolidated dunes on the northern part of the island.
These deposits are 1–5 m thick where mapped on Pakeho‘olua cone, a small Ki‘eki‘e shield vent emplaced about 0.52 Ma that now forms the northern quarter of Ni‘ihau.