4/10/18. Kaua i: probably the most complicated and leastunderstood of the major Hawaiian islands. Today s plan. What are the effects, if modeled?

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1 4// Kaua i: probably the most complicated and leastunderstood of the major Hawaiian islands Today s plan Some more landslides Kauai, part today What are the effects, if modeled? Model as sliding block within the area mapped Ward SN () Landslide Tsunami J Geophys Res 6:

2 4// Tsunami moving across the ocean Predicts large waves here and across the Pacific Ward SN () Landslide Tsunami J Geophys Res 6: The popular case more potential damage Kilauea is moving like a slump, Canary Islands seem ready to slide Ward SN, Day S () Cumbre Vieja Volcano Potential collapse and tsunami at La Palma, Canary Islands Geophys Res Lett :74 La Palma, Canaries Ward & Day () One of the steepest slopes among volcanic islands South rift already shows cracks Hyaloclastites known to exist deep down

3 4// Supposed problem for the East coast Note runup = how far water pushes up on land, not wave height in open ocean what would this do to NE USA? Supposed problem for the East coast Again large waves locally, and across the ocean s of meters would ruin a lot along the E coastline However Not based on real science: Slide/slump not a single event Waves decrease in size much faster

4 4// Kalalau Valley Nā Pali coast Olokele plateau Līhu e Basin Mānā plain Waimea Canyon Old model of volcanic structure i pal Na Olokele Olokele caldera defined by: faults, thick flat lavas Waimea canyon Þ Napali = shield, Olokele fills the crater in the shield volcano But gravity suggests crater in Līhu e Basin, not Olokele Plateau (grey) Makes sense in the broader gravity picture Diagram by Flinders et al () Diagram by Krivoy et al (6) 4

5 4// Kauai, Hawaii With the gravity maximum there, what is the Lihue Basin? secondary caldera? Landslide scar? Preferentially eroded volcano center? Kalalau Valley Nā Pali coast Olokele plateau Mānā plain Līhu e Basin Three sequences in Waimea Canyon Waimea Canyon Sherrod et al, 7; USGS Ages Napali is oldest, Olokele is next, Makaweli seems last shield All followed by rejuvenated Koloa, though there seems to be some overlap Waimea Canyon Basalt Koloa Volcanics

6 4// Volcanic stages Volcano HAWAIIAN ISLANDS STAGES AND AGES Volcanic Stage Shield Kīlauea Mauna Loa Hualālai Mauna Kea Kohala E Maui Puna Pāhala Ash Hilina Ka u Kahuku Nīnole Hualālai Hamākua Pololū Honomanū? PostShield Cap ~ 4 + 4? A D L 7 a u p ā h o Kaua i Ni ihau Wailuku L Member Lāna i L Member Ko olau Kamaile unu Lualualei Makaweli Olokele Haupu Napali Paniau 6?? e h o e? 4 Hawī 6 6 K u l a H W Maui Kaho olawe Lāna i E Moloka i W Moloka i Ko olau Wai anae Rejuvenation ā n a Honolua U Member ~ ~ Lahaina 6 U Member Kalaupapa ~ Honolulu 6? Koloa 6 ~ Ki eki e Kolekole Pālehua 6 Not every volcano has every stage Some volcanoes skip a stage Some volcanoes die young Names with ages listed under stages are the names of mapped geological units Submarine structures Lots of reflective seafloor material around Kaua i means? GLORIA sonar backscatter data Connection Lihue topography and submarine bathymetry: landslide! The twovolcano model of Holcomb et al [7] different models shown; only volcanosolutions can explain that W vs E flanks are compositionally distinct W E 6

7 4// An excellent illustration of the volcano scenario for the development of Kaua i (see book) Collapse of existing volcano leads to build up of lava against old cliff Erosion particularly affects the E side; windward side, landslide? Ponded flatlying lavas remain up top Avalanche scarp N flank of younger volcano wavecut cliff West flank of older volcano lavas ponded between avalanche scar and W flank of younger volcano preferrentially eroded central part of younger volcano old wavecut cliff SW flank of younger volcano Waimea Canyon (diverted wflowing streams off the younger volcano and concentrated their flow, thereby concentrating erosion) Kalalau valley, its mouth is ~halfway along the Nā Pali coast 7

8 4// Old Nā Pali lavas near Kalalau valley Awa awapuhi valley its walls expose old Nā Pali lavas Old Nā Pali lavas exposed in the wall of Awa awapuhi valley

9 4// Dikes Picture