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Geology and ground-water resources of the island of Molokai, Hawaii, Hawaii Division of Hydrography

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... Bottom panel B: Correcting the swath bathymetry for tilting of 1 • towards 150 • about the white cross hairs (at 800 m) restores the paleo-shoreline slope break to horizontal at 810 mbsl, removes its present E-W gradient of 1:100, and reveals what was once a central, flat, lava delta (now at 800-810 mbsl). Prior to this work, our understanding of the geology of Molokaʻi and its submarine extensions was that they comprise two shield volcanoes, West and East (Stearns and Macdonald, 1947), with three rift zones and a former SSB now submerged and tilted to the SSE: Penguin Bank, the NW rift zone and SSB 7b were associated with West Molokaʻi whereas Paʻuwela Ridge and SSB 7a were associated with East Molokaʻi (Sinton et al., 2017;Taylor, 2019; and references therein). Both volcanoes have had their volcanic strata divided into shield-building and post-shield phases of geologic evolution. ...
... Both volcanoes have had their volcanic strata divided into shield-building and post-shield phases of geologic evolution. On West Molokaʻi these are the West Molokaʻi Volcanics (shield), and Waiʻeli Volcanics (postshield) (Sinton et al., 2017;Sherrod et al., 2021) while East Molokaʻi has been divided into a Lower Member (shield) and Upper Member (postshield) of the East Molokaʻi Volcanics (Stearns and Macdonald, 1947;Sherrod et al., 2021). Postshield units on both Molokaʻi volcanoes are chemically evolved, phenocrytst-poor alkalic lavas. ...
... This raises the intriguing question of whether or not the northwest-trending submarine ridge might be structurally related to East Molokaʻi, rather than to West Molokaʻi. Stearns and Macdonald (1947) described a NW rift zone for West Molokaʻi volcano based on a concentration of eruptive vents and divergent lava flow directions on either side of a broad northwesttrending axis that intersects the shoreline between ʻĪlio and Mokio Points (Fig. 9), where a concentration of dikes strikes close to N30W (Stearns and Macdonald, 1947;Sherrod et al., 2021). That rift zone can be traced offshore NW from ʻIlio Point to about the 100-m depth contour (Fig. 9A, Fig. 10). ...
... Molokaʻi, the fifth largest island in the Hawaiian chain, is situated between 21°00'-21°15' N and 157°20'-156°40' W with an area of 673 km 2 (Figure 2) (Stearns and Macdonald, 1947). The population in 2020 was 6,253 (County of Maui, 2020). ...
... The population in 2020 was 6,253 (County of Maui, 2020). The island is largely composed of the 423 m-high, West Molokaʻi volcano and the younger, 1,512 m-high, East Molokaʻi volcano (Stearns and Macdonald, 1947). Molokaʻi has a mean annual temperature of 23.91°C (1978Giambelluca et al., 2014). ...
... The ranking was as follows: <30 cm from land surface to groundwater = 5; 31-50 cm = 3; >50 cm = 1. The second measure was the range of estimated groundwater (gw) discharge at the coastline (Oki et al., 2019) and/or the number of springs mauka of the site (Stearns and Macdonald, 1947). The gw discharge/spring ranking was as follows: >500,000 gallons gw discharge/day and the presence of springs/seeps mauka of site = 5; 100,000-500,000 gallons of gw discharge/day and springs on site = 3 or high gw discharge at the coast but no springs on site = 3; low gw discharge (<500,000 gallons/day) and no springs on site = 1. ...
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Hawaiian coastal wetlands provide important habitat for federally endangered waterbirds and socio-cultural resources for Native Hawaiians. Currently, Hawaiian coastal wetlands are degraded by development, sedimentation, and invasive species and, thus, require restoration. Little is known about their original structure and function due to the large-scale alteration of the lowland landscape since European contact. Here, we used 1) rapid field assessments of hydrology, vegetation, soils, and birds, 2) a comprehensive analysis of endangered bird habitat value, 3) site spatial characteristics, 4) sea-level rise projections for 2050 and 2100 and wetland migration potential, and 5) preferences of the Native Hawaiian community in a GIS site suitability analysis to prioritize restoration of coastal wetlands on the island of Molokaʻi. The site suitability analysis is the first, to our knowledge, to incorporate community preferences, habitat criteria for endangered waterbirds, and sea-level rise into prioritizing wetland sites for restoration. The rapid assessments showed that groundwater is a ubiquitous water source for coastal wetlands. A groundwater-fed, freshwater herbaceous peatland or “coastal fen” not previously described in Hawaiʻi was found adjacent to the coastline at a site being used to grow taro, a staple crop for Native Hawaiians. In traditional ecological knowledge, such a groundwater-fed, agro-ecological system is referred to as a loʻipūnāwai (spring pond). Overall, 39 plant species were found at the 12 sites; 26 of these were wetland species and 11 were native. Soil texture in the wetlands ranged from loamy sands to silt and silty clays and the mean % organic carbon content was 10.93% ± 12.24 (sd). In total, 79 federally endangered waterbirds, 13 Hawaiian coots (‘alae keʻokeʻo; Fulica alai) and 66 Hawaiian stilts (aeʻo; Himantopus mexicanus knudseni), were counted during the rapid field assessments. The site suitability analysis consistently ranked three sites the highest, Kaupapaloʻi o Kaʻamola, Kakahaiʻa National Wildlife Refuge, and ʻŌhiʻapilo Pond, under three different weighting approaches. Site prioritization represents both an actionable plan for coastal wetland restoration and an alternative protocol for restoration decision-making in places such as Hawaiʻi where no pristine “reference” sites exist for comparison.
... A few weak explosions have occurred. The surface of ML originates mostly from the Holocene (Stearns and Macdonald, 1946;Lipman and Swenson, 1984). Stearns and Macdonald (1946) divided the volcano's rocks into Pliocene Ninole basalt, Pleistocene Kahuku basalt, and Pleistocene and Holocene Kau basalt (the most recent). ...
... The surface of ML originates mostly from the Holocene (Stearns and Macdonald, 1946;Lipman and Swenson, 1984). Stearns and Macdonald (1946) divided the volcano's rocks into Pliocene Ninole basalt, Pleistocene Kahuku basalt, and Pleistocene and Holocene Kau basalt (the most recent). ...
... The configurations of cinder cones indicate the location of less-defined southerly, easterly, and westerly rifts. The volcano's rocks were divided into two volcanic series by Stearns and Macdonald (1946). The older (Hamakua) series forms a major part of the mountain and represents the shield stage and part of the post-shield stage. ...
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This study used land gravity and airborne magnetic data to investigate the depth to the magmatic chamber and map the heat flow distribution beneath the active volcanoes of Hawaii Island using the Curie point depth (CPD) and gravity modeling. Obtaining some of the ground-based geophysical measurements was problematic due to accessibility limitations; therefore, this study used available data. The CPD and magnetic data were used to map the depth to the bottom of the magnetic layer by calculating the depth to the Curie isotherm (540°C) beneath Hawaii Island. The spectral peak method was used to calculate the depths to the shallow and deep magnetic sources for the entire island, and the CPD was calculated using the centroid method. A two-dimensional density model for two Earth layers was constructed using forward modeling of the gravity data. A large plume of dense intrusive material was observed beneath the three adjacent volcanoes of Mauna Loa, Mauna Kea, and Kilauea, and two small chambers were found to be located beneath the Kohala and Hualalai volcanoes. Based on the gravity modeling results, the depth to the magma layer varied from 0.5 to 10 km, and the heat flow was higher close to the volcanic eruption zones. The current study is informative and cost effective for the world’s most active volcanic areas.
... A few weak explosions have occurred. The surface of ML originates mostly from the Holocene (Stearns and Macdonald, 1946;Lipman and Swenson, 1984). Stearns and Macdonald (1946) divided the volcano's rocks into Pliocene Ninole basalt, Pleistocene Kahuku basalt, and Pleistocene and Holocene Kau basalt (the most recent). ...
... The surface of ML originates mostly from the Holocene (Stearns and Macdonald, 1946;Lipman and Swenson, 1984). Stearns and Macdonald (1946) divided the volcano's rocks into Pliocene Ninole basalt, Pleistocene Kahuku basalt, and Pleistocene and Holocene Kau basalt (the most recent). ...
... The configurations of cinder cones indicate the location of less-defined southerly, easterly, and westerly rifts. The volcano's rocks were divided into two volcanic series by Stearns and Macdonald (1946). The older (Hamakua) series forms a major part of the mountain and represents the shield stage and part of the post-shield stage. ...
Article
Full-text available
This study used land gravity and airborne magnetic data to investigate the depth to the magmatic chamber and map the heat flow distribution beneath the active volcanoes of Hawaii Island using the Curie point depth (CPD) and gravity modeling. Obtaining some of the ground-based geophysical measurements was problematic due to accessibility limitations; therefore, this study used available data. The CPD and magnetic data were used to map the depth to the bottom of the magnetic layer by calculating the depth to the Curie isotherm (540°C) beneath Hawaii Island. The spectral peak method was used to calculate the depths to the shallow and deep magnetic sources for the entire island, and the CPD was calculated using the centroid method. A two-dimensional density model for two Earth layers was constructed using forward modeling of the gravity data. A large plume of dense intrusive material was observed beneath the three adjacent volcanoes of Mauna Loa, Mauna Kea, and Kilauea, and two small chambers were found to be located beneath the Kohala and Hualalai volcanoes. Based on the gravity modeling results, the depth to the magma layer varied from 0.5 to 10 km, and the heat flow was higher close to the volcanic eruption zones. The current study is informative and cost effective for the world’s most active volcanic areas.
... Rings of concentric dikes marked by lines of vents nearly encircle the caldera rim (Chadwick and Howard, 1991). These dikes must act as groundwater barriers, much like the linear rift-zone dikes on Hawai'i's basaltic volcanoes (Stearns and MacDonald, 1946). Assuming a groundwater level near the pre-eruption lake surface, and a storage area of 20-30 × 10 6 m 2 defi ned by the area confi ned within the circumferential lines of vents, the ~100 × 10 6 m 3 of groundwater that rapidly discharged onto the collapsed fl oor within 2 wk of caldera collapse had been stored in a rock volume of 5-10 km 3 , representing 1-2 vol% readily available water in addition to water lost in the eruption. ...
... Although textbook cases of hydromagmatic eruptions occur when ascending magma encounters groundwater or surface water, other hydromagmatic eruptions relate to withdrawal or lowering of magma in a conduit. The withdrawal of magma creates a pressure gradient in a highly permeable substrate, forcing groundwater to fl ow into and encounter hot rocks in a vent area (Stearns and MacDonald, 1946;Swanson and Christiansen, 1973;Hildreth, 1991;Dvorak, 1992;Dzurisin et al., 1995;Swanson et al., 2012aSwanson et al., , 2012b. ...
... At Kīlauea Volcano, phreatic and hydromagmatic eruptions have long been recognized as associated with falling summit magma levels (Jagger, 1924;Stearns and MacDonald, 1946). Kīlauea Volcano's multiple episodes over centuries of hydromagmatic and phreatic eruptions generally occur when magma levels in a deepened caldera fall near or below the water table 600 m below the modern caldera rim (Swanson and Christiansen, 1973;Decker and Christiansen, 1984;Dvorak, 1992;Dzurisin et al., 1995;Swanson et al., 2012aSwanson et al., , 2012b. ...
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The hydromagmatic eruption that immediately preceded the 1968 caldera collapse of Fernandina Volcano, Galápagos, which had a volcano explosivity index (VEI) of 4, offers a case study of powerful eruptions where basaltic magma interacts with caldera-ponded water. The 4-d-long hydromagmatic eruption sequence records an early stage and a small fraction of the volume of magmatic withdrawal that led the caldera floor to lower 350 m over the next 10 d. Erupted tephra was lithic-rich. The small proportion of juvenile basaltic glass included blocky fragments, Pele’s tears, and Pele’s hair. Pyroclastic density currents swept across the western summit plateau 600–700 m above the vent and deposited dunes, cross-bedded and rubbly breccia deposits, imbricated lag blocks, and ash plasters, and toppled trees. Blocks ejected out of the caldera formed impact craters on the volcano’s flank >600 m higher and >1 km away. Ejected blocks are mostly basalt but include cumulate olivine gabbro. The vent area enlarged by 300 × 106 m3 during the eruption. A small adjacent fault-bounded block subsided after the eruption. Lake water and groundwater confined within the caldera by ring dikes were available to interact with hot rocks and magma. In our interpretation, this water helped to trigger and feed the eruption by interacting with rocks above a lowering magma column. Ecosystems recovered rapidly on the tephra. Eruptions have not diminished the island’s biodiversity despite Fernandina’s high rate of volcanic activity, including the massive resurfacing in 1968. Stratigraphic evidence suggests that the 1968 eruption may be only the latest in a series of explosive eruptions from the caldera.
... The expanded chemical data constrained by field relations of Macdonald (1968) demonstrated conclusively that the latter part of the highly effusive shield stage is characterized by lava successions in which alkalic basalts first appear, commonly interbedded with tholeiitic lavas, and some sequences include samples that are chemically gradational (compositionally transitional) in character (Macdonald, 1968;Diller, 1982;Feigenson et al., 1983;Sinton, 1987;Zbinden and Sinton, 1988;Frey et al., 1990;Chen et al., 1991;Wolfe et al., 1997). In each case these sequences all are in the upper parts of stratigraphic units that were designated as shield-stage sequences, e.g., Wailuku Basalt of West Maui (Stearns and Macdonald, 1942), Pololū Basalt of Kohala (Stearns and Macdonald, 1946), Lower Member of the East Moloka'i Volcanics (Stearns and Macdonald, 1947), Honomanū Volcanics of East Maui (Stearns and Macdonald, 1942), Hāmākua Basalt of Mauna Kea (Stearns and Macdonald, 1946), Kamaile'unu Member of the Wai'anae Volcanics (Sinton, 1987). Thus, two different evolutionary "events" characterize the declining eruptive phases of Hawaiian volcanoes -the period of compositional transition to alkalic volcanism (within the upper parts of sequences mapped as shield successions), and the change in lava flow color and thickness and the nature of eruptions that are the signature of mapped postshield stratigraphic units. ...
... Not all Hawaiian volcanoes are equally well mapped, and most lack sufficient petrological study to quantitatively assess depths of magma evolution. Stearns and Macdonald (1947) using digital compilation of Sherrod et al. (2007b). Index in upper left corner shows area of this figure. ...
... Moloka'i is composed of two major shield volcanoes, designated East and West Moloka'i by Stearns and Macdonald (1947). The island's eastwest elongate shape and spectacular sea cliffs on the north side resulted from removal of a significant portion of the island during major mass wasting that formed the Wailau Slide deposit (Moore et al., 1989). ...
Article
New mapping, geochronology and petrological investigations reveal that the two volcanoes of the island of Moloka‘i, Hawai‘i exhibit striking contrasts in composition and volcanic production in the waning stages of their activity. Postshield lava extrusion on West Moloka‘i produced less than 1 km3 of alkalic basalt and hawaiite, most likely in less than 100 k.y, beginning ~1.8 Ma.West Moloka‘i is unique among Hawaiian volcanoes that reached the postshield stage of evolution in lacking a protracted period of transitional volcanism in the late shield stage. Petrological modeling indicates that volatile-poor (<0.5wt % H2O) West Moloka‘i postshield magmas evolved in reservoirs in the upper mantle, 20-26 km beneath the summit. In contrast, following a protracted transitional period, East Moloka‘i extruded postshield magmas ranging from hawaiite to benmoreite that evolved in magma reservoirs lying within the crust, 11- 17 km beneath the summit. Parental magmas to the East Moloka‘i postshield were hydrous and enriched in phosphorous and Sr (2.5 wt % P2O5, 2500 ppm Sr at 6 wt % MgO, 45 wt % SiO2), a magma type known previously only from Kohala volcano. Although the overall volume of East Moloka‘i volcano is less than that of West Moloka‘i, its proportion of postshield extrusives is greater by a factor of 8, and its postshield volumetric production rate (~155 km3/m.y.) is greater than that at West Moloka‘i by a factor of 3. The lower volume and deeper magmatic evolution of the West Moloka‘i postshield compared to that of East Moloka‘i is consistent with a thermally controlled relationship between magma supply, as inferred from volcanic production rate, and magma reservoir depth.
... Post-shield alkaline lavas constitute about 1% of the lavas on the Hawaiian Islands (Clague 1987). On East Maui, these lavas erupted on top of the voluminous shield- stage tholeiitic lavas from vents along the southwest, east, and north rift zones, and in the Haleakala Crater at the triple junction of the three rifts ( Fig. 5.1a; Stearns and Macdonald 1942). A large number of post-shield volcanic vents are located in the southwest and east rift zones, whereas, only a few post-shield vents are located in the north rift zone indicating that the north rift remained inactive as a failed arm of the triple-junction rifts during the post-shield stage (Bhattacharji and Koide 1975). ...
... A large number of post-shield volcanic vents are located in the southwest and east rift zones, whereas, only a few post-shield vents are located in the north rift zone indicating that the north rift remained inactive as a failed arm of the triple-junction rifts during the post-shield stage (Bhattacharji and Koide 1975). The post-shield alkaline lavas have been subdivided into an older Kula series and a younger Hana series on the basis of stratigraphy (Stearns 1942;Stearns and Macdonald 1942;Macdonald 1978). The Hana series was earlier regarded as a product of rejuvenated volcanism following a period of quiescence after the eruption of the Kula series (Clague and Dalrymple 1987). ...
... In this study, we examine geological features, mode of eruptions, and geochemical characteristics of Kolekole lavas as an example of Hawaiian post-shield volcanism. Stearns (1942) and Stearns and Macdonald (1942) originally studied the geological and geomorphological features of Haleakala volcano and the geology of East Maui. Macdonald and Katsura (1964) later studied the geology and petrology of lavas erupted along the rift zones of East Maui. ...
Article
The Kolekole cinder cone is located in the southwest rift zone near the triple-junction of the southwest, east and north rifts, and the Haleakala volcano summit area in East Maui, Hawaii. The geochemical and petrological characteristics of the alkaline lavas erupted from the cinder cone provide important information regarding the post-shield evolution of Hawaiian volcanoes. The incompatible element abundances and ratios of the Kolekole lavas are transitional between previously studied post-shield, temporally continuous, Kula and Hana alkaline series. Thus, the incompatible element composition of the alkaline lavas changed gradually during the post-shield stage. Rare earth element ratios such as Tb/Yb indicate that the Kolekole post-shield alkaline lavas originated from garnet-bearing mantle source regions. The Kolekole lavas are predominantly ankaramite containing 25-40% by volume, large (1-5 mm), normal and reverse-zoned olivine and augite phenocrysts. About 74-85% of the olivine and 58-75% of the augite phenocrysts are reversely zoned. The groundmass of the ankaramite is basanitic and similar to alkaline lava elsewhere on East Maui. Barometry indicates that the phenocrysts originated from depths between 15.5 and 48 km, transcending the crust-mantle boundary. The alkaline primary magma probably ponded below solidified, shallow, shield-stage magma chambers and underwent extensive olivine-controlled high pressure fractional crystallization, as indicated by the Fe-rich (Mg# 35-49) composition estimates and major and compatible trace element correlations in the ankaramite groundmass. Large spheroidal bombs (0.6-2.2 m) near the Kolekole vents indicate that the evolved magma eventually erupted by violent volatile-driven explosions.
... A volcanic hiatus occurred at the end of the Honomanu period, 0.93 million years ago, during which the Honomanu surface was eroded into incised valleys and covered by a red, ashy soil (Stearns and MacDonald, 1942). This surface was then buried by the post-shieldstage, Kula Volcanics. ...
... The Kula Volcanics are ankaramite and alkali basalt in composition and range in age from 0.36 to 0.93 million years. The unit is thickest near the summit of Haleakala Volcano, where it reaches a thickness of 600 m or more and tappers to a thickness of 40 m in the isthmus between the two volcanoes (Stearns and MacDonald, 1942). Individual flows and clinker beds of the Kula Volcanics are thicker and contain less void space than the flows of the Honomanu Basalt and are separated by numerous erosional surfaces and buried soils, particularly near the top of the formation. ...
... Hence, the contrast between the horizontal and vertical hydraulic conductivity of the Kula Volcanics is likely greater than that of the underlying Honomanu Basalt (Gingerich, 1999b). Stearns and MacDonald (1942) reported that the Kula Volcanics are weathered to saprolite to a depth of 15 m, high on the northern flank of Haleakala Volcano, where precipitation ranges between 1,200 to 1,300 mm/yr. At lower elevations, where the precipitation is less, the Kula Volcanics are significantly less weathered. ...
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In this study, we use a combination of electrical resistivity profiling and radon (222Rn) measurements to characterize a shallow groundwater system beneath the last remaining, large scale sugarcane plantation on Maui, Hawaii. Hawaiian Commercial & Sugar Company has continuously operated a sugarcane plantation on the western flank of Haleakala Volcano since 1878. The sugarcane is irrigated with a combination of surface water brought through tunnels from the wetter, eastern flank of Haleakala Volcano and groundwater from wells within the plantation. To assess the flow of irrigation water through the shallow subsurface, we collected a representative topo-sequence of four 2-D resistivity profiles that sample different topographic and hydrologic settings within the plantation. The profiles show a down-slope-thickening (0 to 20 m), surficial low-resistivity (10-200 Ohm-m) layer extending from the upslope limit of irrigated sugarcane to the lowest elevations of the plantation. At a canal crossing, the low resistivity layer thickens and is less resistive upslope of the canal. Beneath a reservoir at mid elevation, the layer thickens to 20 m and curves down slope beneath the reservoir and up to the base of the field beyond. At the base of the slope, the low resistivity layer is 20-m thick below both fields and a second reservoir. An increase in radon concentration in the down-flow direction within the canal system at one location suggests groundwater infiltration into the canal. We attribute the low-resistivity layer to irrigation water that has infiltrated below the root zone and leaked from canals and reservoirs within the plantation. The water flows down slope to the base of the slope and there flows vertically, recharging the basal aquifer. We suggest that seepage from the canals and reservoirs is in part controlled by the local pressure head within the shallow flow system.
... The Island of Hawai'i, also referred to as the "Big Island," is largest of the Hawaiian Islands (Figure 3). At its greatest dimension, the island is 150 km (93mi) across with a total land area of 10,432 km 2 (4,028 mi 2 The geology of the Big Island reflects four stages of volcanism (Stearns, 1946) as identified from surface and subsurface rock samples. Specially, during the initial submarine stage (stage 1) small vents or fissures open in the ocean floor and erupt pillow lavas that have higher relative abundances of sodium and potassium than the tholeiitic basalts of the shield-building stage. ...
... Mauna Kea is an example of a volcano with multiple steep sided (25-33 degrees) cinder cones. The rocks of Hawai'i island are considered highly permeable resulting in rapid rainfall infiltration into the subsurface (Stearns, 1946). Perennial streams are present only on the western slopes of Kohala Mountain and Mauna Kea. ...
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The availability of freshwater and low-cost electricity are two limiting factors for sustainable living in Hawai'i and worldwide. This fact raises the question: Can technology be developed to locate freshwater and geothermal resources simultaneously? We present a multimodal machine learning (MML) workflow to assimilate and simultaneously predict the 3d distribution of numeric and categorical features (field observations) along a groundwater-geothermal continuum. Success of the MML workflow relies on a transductive learning algorithm that projects field modalities onto a single embedding space (hypersurface). Multimodalities can include any combination of measured (point field) and derived (multiphysics-based numerical model inversions, data-driven machine learning, and multiphysics-informed machine learning) features. The proposed MML workflow is applied to assimilate randomly shuffled subsets of Hawai'i Play Fairway modalities and predict subsurface geophysical, geologic, and hydrogeologic features at the Islands of Lāna'i and Hawai'i. Despite challenging field data characteristics (disparate, scale dependent, spatially limited, sparse, and uncertain), the MML workflow yields a single 3d transdisciplinary model that generalizes well to independent data presented to the trained model. The predicted features are used to identify hidden groundwater and geothermal resources at Lāna'i, and geothermal resources at Hawai'i. Other interpreted subsurface features at Lāna'i include basalt, batholith, dike swarm, pluton, sill, mantle, Moho, and 3d geothermal stratigraphic units; whereas interpreted subsurface features at Hawai'i include 3d velocity layering, 3d earthquake-fault associations, 3d fault systems; basalt, oceanic crust, magmatic underplating, lithospheric flexure, mantle, and Moho. This study provides new capabilities for characterizing continuous subsurface groundwater and geothermal features for sustainable living in the Hawai'ian Islands and other geothermal sites worldwide. Keywords: Multimodal machine learning, 3d geothermal stratigraphic units, 3d hidden groundwater resources, 3d hidden geothermal resources 3d velocity layering, 3d earthquake-fault associations, 3d fault systems; basalt, batholith, dike swarm, oceanic crust, pluton, sill, magmatic underplating, lithospheric flexure, mantle, Moho, Island of Lāna'i, Island of Hawai'i
... The West Maui Volcano is predominantly made up of shield lavas of the Wailuku Basalts (Gaffney et al., 2004) and the thin postshield cap of the Honolua Volcanics (Stearns and Macdonald, 1942;Sherrod et al., 2007). Wailuku shield volcanism on West Maui was active from 2.1 to 1.35 Ma and was soon thereafter followed by the brief Honolua postshield stage which lasted from 1.35 to 1.2 Ma (Sherrod et al., 2007). ...
... The Lahaina Volcanics erupted in two pulses, one at ~0.4 Ma and one at ~0.6 Ma (Tagami et al., 2003), resulting in four discrete cinder cones on the southwest flank of the volcano; Pu'u Hele located 4.5 km northeast of McGregor Point, Pu'u Kīlea in Olowalu Valley, Pu'u Laina near Lahaina, and Keke'a Point about 6 km north of Lahaina (Fig. 1b). Of the four locations, only the Puʻu Laina cone erupted a significant lava flow that extends offshore (Stearns and Macdonald, 1942). As is typical for the rejuvenated stage, the Lahaina vents have no relation to the structures (e.g., rift zones) that concentrate shield and postshield activity (Diller, 1982;Sinton, 2019). ...
Article
The study of rejuvenated-stage volcanism provides insight into spatiotemporal changes to the geochemical structure of the Hawaiian mantle plume and the varying interaction with non-plume sources over an extended period of melting beneath volcanic centres. We present new geochemical and Hf-Pb-Sr-Nd isotopic data from 6 samples of rejuvenated-stage volcanism on West Maui, the southernmost and youngest island within the Hawaiian chain to exhibit rejuvenation. Major and trace element geochemistry reveal four discrete silica undersaturated eruptions produced by 3-11% partial melting of a garnet peridotite mantle source of metasomatized upper asthenosphere. High Ba/Th ratios (>200) overlap with rejuvenated-stage lavas from Niʻihau, indicating that a minor carbonatite presence persists within the source of rejuvenated-stage lavas along the Hawaiian chain. Puʻu Laina lavas on West Maui have εHf = +15 and εNd = +8.9, which are among the most depleted values of rejuvenated lavas and plot on or below the terrestrial mantle array. These values are close to that of the most depleted lavas from the North Arch and along with rejuvenated lavas from Kauaʻi and East Molokaʻi trend towards the Pacific MORB. Pyroxenite xenoliths and lavas from Kaʻula and Oʻahu, and lavas from Niʻihau extend to higher εHf values at a given εNd indicating a long-lived depleted source independent of the MORB mantle. West Maui rejuvenated lavas form a steep 208Pb/204Pb-206Pb/204Pb trendline and together with North Arch and East Molokaʻi lavas are shifted towards lower 208Pb/206Pb values typical of Pacific MORB. We propose that the across-plume heterogeneity seen in rejuvenated lavas on Kauaʻi and Niʻihau persists at the southern end of the Hawaiian chain where West Maui and East Molokaʻi rejuvenated lavas, like Kauaʻi and North Arch, preferentially source upper asthenosphere as opposed to an ancient depleted source. This across-plume heterogeneity within rejuvenated-stage lavas closely resembles the Kea and Loa-trend differences in shield stage geochemistry and indicates that similar geodynamic processes are responsible for both.
... It is composed of two coalescing volcanoes, West Molokai Volcano, which rises 421 m above sea level, and the younger East Molokai Volcano, which rises 1515 m above sea level. Stearns and Macdonald (1947) Stearns (1946) and Stearns and Macdonald (1947) showing the Kalaupapa Peninsula on the north-central coast and Mokuhooniki Island off the east coast. The sample locations are shown on the enlarged map of the Kalaupapa Peninsula. of the post-caldera alkalic stage. ...
... It is composed of two coalescing volcanoes, West Molokai Volcano, which rises 421 m above sea level, and the younger East Molokai Volcano, which rises 1515 m above sea level. Stearns and Macdonald (1947) Stearns (1946) and Stearns and Macdonald (1947) showing the Kalaupapa Peninsula on the north-central coast and Mokuhooniki Island off the east coast. The sample locations are shown on the enlarged map of the Kalaupapa Peninsula. of the post-caldera alkalic stage. ...
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The post-erosional Kalaupapa Basalt on East Molokai, Hawaii, erupted between 0.34 and 0.57 million years ago to form the Kalaupapa Peninsula. The Kalaupapa Basalt ranges in composition from basanite to lava transitional between alkalic and tholeiitic basalt. Rare-earth and other trace-element abundances suggest that the Kalaupapa Basalt could be generated by 11-17% partial melting of a light-REE-enriched source like that from which the post-erosional lavas of the Honolulu Group on Oahu were generated by 2-11% melting. The ⁸⁷Sr/⁸⁶Sr ratios of the lavas range from 0.70320 to 0.70332, suggesting that the variation in composition mainly reflects variation in the melting process rather than heterogeneity of sources. The length of the period of volcanic quiescence that preceded eruption of post-erosional lavas in the Hawaiian Islands decreased as volcanism progressed from Kauai toward Kilauea. - Authors
... are similar to those of sample C-159 (Figs. 3, 4), a lava sample from the Hawaiian island of Moloka'i (Macdonald, 1968). Thus, our initial interpretation was that the source rock for adze 1986.602 was the same lava flow as Macdonald's sample C-159, a lava flow from Pu'u Pāpa'i, which is part of the Upper Member of the East Moloka'i Volcanic Series (Stearns and Macdonald, 1947). To test this hypothesis we collected new samples from Pu'u Pāpa'i (Fig. 4), and studied them using the same analytical procedures as for adze 1986.602. ...
... The lower part of the flow is cut by the modern highway, and the region below the road now hosts a mangrove thicket. However, the close proximity of the flow to a coastal region characterized by several fish Fig. 4. Geologic map of the region near Pu'u Pāpa'i, East Moloka'i, modified after Stearns and Macdonald (1947). Locations of all samples discussed in this paper are shown. ...
Article
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An unusually long and flat adze found in the ocean off O'ahu Hawai'i has distinctive micro-texture, including ap-atite microphenocrysts, and unusual chemical composition with ~2.5 wt.% P 2 O 5. The 37-cm-long adze is among the largest in the Bishop Museum collection and has a relatively flat, un-tanged morphology reminiscent of ancient adzes from the Marquesas Islands. However, the petrologic characteristics of the adze match exactly those of a lava flow erupted from Pu'u Pāpa'i on the Hawaiian island of Moloka'i, including microtexture, whole-rock composition and the chemistry of included apatite crystals. These data indicate that the adze and the Pu'u Pāpa'i lava are indistinguishable, strongly suggesting the presence of a previously unrecognized adze quarry on East Moloka'i. New field investigations revealed working areas on Pu'u Pāpa'i, consisting of large flakes and cores showing evidence of percussion. Although our data strongly support the hypothesis that this unusual adze was fabricated on Moloka'i, they do not explain why the adze has a nearly unique morphology for Hawaiian adzes, nor its age. This study uses a novel approach to determining the adze source, utilizing distinctive petrog-raphy, major element composition and mineral chemistry to indicate a previously unknown adze source in the Hawaiian Islands.
... Although the quarry requires an archaeological survey to locate the boundaries and map internal details, there are cores (up to 30 cm long), adze blanks and likely preforms, and debitage scattered over ~200 m east-west by 50 m north-south towards the base of a broad slope that is truncated by the coastal highway (Sinton & Sinoto 2015: Figures 4 and 7). Pu'u Pāpa'i is part of the Upper Member of the East Moloka'i Volcanics (Sherrod et al. 2021;Stearns and Macdonald 1947), situated just inland from the south-central shoreline ( Figure 1). Although thinsections and apatite composition were reported by Sinton and Sinoto (2015), of interest here are six samples that were Journal of Pacific Archaeology -Vol. ...
Article
Chemically characterising stone tools in distant habitation sites and matching artefacts to quarries is some of the strongest evidence archaeologists have to define the spatial and temporal limits of ancient interaction networks. We present the chemical analysis of five basalt flakes from three sites on Moloka‘i, Hawaiian Islands: a well-dated colonisation period stratified coastal mound, a craft specialisation locale and an upland buried habitation. Wavelength dispersive x-ray fluorescence (WDXRF) and inductively coupled plasma mass spectrometry (ICP-MS) was used to identify the origin of the artefacts. Radiocarbon dating results indicate that the recently discovered Pu‘u Pāpa‘i (Moloka‘i) quarry was likely utilised from the colonisation period beginning in the 12th century through to the late 1600s, making it one of the oldest, continuously used quarries in the archipelago. Aspects of island colonisation and community networks are discussed including the emergence of the elite control of resources.
... Although the quarry requires an archaeological survey to locate the boundaries and map internal details, there are cores (up to 30 cm long), adze blanks and likely preforms, and debitage scattered over ~200 m east-west by 50 m north-south towards the base of a broad slope that is truncated by the coastal highway (Sinton & Sinoto 2015: Figures 4 and 7). Pu'u Pāpa'i is part of the Upper Member of the East Moloka'i Volcanics (Sherrod et al. 2021;Stearns and Macdonald 1947), situated just inland from the southcentral shoreline (Figure 1). Although thin-sections and apatite composition were reported by Sinton and Sinoto (2015), of interest here are six samples that were collected Journal of Pacific Archaeology -Vol. ...
Article
Full-text available
Chemically characterising stone tools in distant habitation sites and matching artefacts to quarries is some of the strongest evidence archaeologists have to define the spatial and temporal limits of ancient interaction networks. We present the chemical analysis of five basalt flakes from three sites on Moloka'i, Hawaiian Islands: a well-dated colonisation period stratified coastal mound, a craft specialisation locale and an upland buried habitation. Wavelength dispersive ×-ray fluorescence (WDXRF) and inductively coupled plasma mass spectrometry (ICP-MS) were used to identify the origin of the artefacts. Radiocarbon dating results indicate that the recently discovered Pu'u Pāpa'i (Moloka'i) quarry was likely utilised from the colonisation period beginning in the 12th century through to the late 1600s, making it one of the oldest, continuously used quarries in the archipelago. Aspects of island colonisation and community networks are discussed including the possible emergence of the elite control of resources.
... Soil is of typical basaltic origin derived from the original shield-building Wailuku Volcanic Series (Stearns and MacDonald 1942). The average annual rainfall is approximately 2700 mm. ...
Article
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Clermontia hanaulaensis H.Oppenheimer, Lorence & W.L.Wagner, sp. nov. , a newly discovered, narrowly distributed endemic species, is herein described based on its morphological characteristics and illustrated with field photos and a line drawing. It is currently known only from the slopes of Hana‘ula, in Pōhākea Gulch, Mauna Kahālāwai, west Maui, Hawaiian Islands. It differs from all other species of Clermontia Gaudich. by the combination of its (2)3–4(–5) flowered inflorescence, violet colored perianth often suffused with creamy white streaks or sometimes creamy white with violet-purple irregular veins, (30)35–45(–50) mm long, perianth tube 15–25(–27) mm long, 9–10 mm wide, the lobes 20–26 mm long, (2–)3–3.5 mm wide, with petaloid calyx lobes 1/2–4/5 as long as the petals. A key to the Clermontia species and subspecies occurring on Maui is provided. Its habitat is described. Its conservation status is proposed as critically endangered (CR), and conservation efforts are discussed.
... While Remy reported that Kauhakō Crater lake contained salty water, Nakuino states that the lake was used as a highly valuable freshwater resource. Similar discrepancies in reporting on the salinity of the lake occurred in later accounts between Mouritz (1943) who reported freshwater resources and Stearns and Macdonald (1947) describing a brackish water lake. While modern scientific investigations into the hydrology and chemistry of Kauhakō Crater lake by Maciolek (1982) and (Donachie et al., 1999) revealed meromictic conditions with strong salinity and temperature stratification, one of the questions that still remains largely unanswered is if there is evidence of a hydrological connection between the open ocean and the crater lake, and what kind of fluxes are associated with both endpoints. ...
Article
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Land-based sources of groundwater pollution can be a critical threat to coral reefs, and a better understanding of "ridge-to-reef" water movement is required to advance management and coral survival in the Anthropocene. In this study a more complete understanding of the geological, atmospheric, and oceanic drivers behind coastal groundwater exchange on the Kalaupapa peninsula, on Moloka'i, Hawai'i, is obtained by analyzing high resolution geochemical and geophysical time-series data. In concert with multiyear water level analyses, a tidally and precipitation-driven groundwater connection between Kauhakō Crater lake and submarine groundwater discharge (SGD) fluxes are demonstrated. Results include an average discharge rate of 190 cm d − 1 and the detection of water-flow pathways past cesspools that likely contribute to higher nutrient loading near the SGD sites. This underlines the importance of managing anthropogenic nutrients that enter the shallow freshwater lens such as through cesspools and are consequently discharged via SGD onto coral reef habitats.
... We explored our data to assess whether geographic range could have led to an overestimation of the threatened status in the IUCN Red List assessments of Kauai SIE. Kauai is 1437 km 2 (Stearns & MacDonald, 1960). Due to its small size, any endemic taxon could at least be considered EN according to criterion B, for example, if a decline is detected and populations are severely fragmented or occur in 5 or fewer locations because EOO is <5000 km 2 . ...
Article
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The International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) is the world's most comprehensive information source on the global conservation status of species. Governmental agencies and conservation organizations increasingly rely on IUCN Red List assessments to develop conservation policies and priorities. Funding agencies use the assessments as evaluation criteria, and researchers use meta‐analysis of red‐list data to address fundamental and applied conservation science questions. However, the circa 143,000 IUCN assessments represent a fraction of the world's biodiversity and are biased in regional and organismal coverage. These biases may affect conservation priorities, funding, and uses of these data to understand global patterns. Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates. The archipelago of Hawaii has one of the highest levels of endemism of any floristic region; 90% of its 1367 native vascular plant taxa are classified as endemic. We used the IUCN's assessment of the complete single‐island endemic (SIE) vascular plant flora of Kauai, Hawaii, to assess the proportion and drivers of decline of threatened plants in an oceanic island setting. We compared the IUCN assessments with federal, state, and other local assessments of Kauai species or taxa of conservation concern. Finally, we conducted a preliminary assessment for all 1044 native vascular plants of Hawaii based on IUCN criterion B by estimating area of occupancy, extent of occurrence, and number of locations to determine whether the pattern found for the SIE vascular flora of Kauai is comparable to the native vascular flora of the Hawaiian Islands. We compared our results with patterns observed for assessments of other floras. According to IUCN, 256 SIE vascular plant taxa are threatened with extinction and 5% are already extinct. This is the highest extinction risk reported for any flora to date. The preliminary assessment of the native vascular flora of Hawaii showed that 72% (753 taxa) is threatened. The flora of Hawaii may be one of the world's most threatened; thus, increased and novel conservation measures in the state and on other remote oceanic islands are urgently needed.
... The Ninole Basalts crop out in several places within the Ninole Hills, on the SE flank of Mauna Loa volcano ( Figure 1). The Ninole Hills are a highly dissected portion of Mauna Loa, and have long been considered a local geomorphic anomaly, comprised of some of the oldest rocks on the island of Hawai'i [61]. ...
... Stearns (1935a, b, c) was the first to study Pleistocene shorelines on the islands of Oahu and Maui, describing benches at elevations of +6 to +10.7 m related to the Late Pleistocene . Beach deposits on Ulupau Head, Oahu, occur up to 10.7 to 12.2 m above present sea level (Stearns, 1935c;Wentworth and Hoffmeister, 1939). Several studies have provided ages for the deposits of the Waimanalo Limestone on Oahu, and Rubin et al. (2000) provided ages for Hulopoe gravel coral clasts on Lanai. ...
Article
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Marine Isotope Stage 5 deposits have been reported on many tropical Pacific islands. This paper presents a database compiled through the review of MIS 5e (last interglacial – LIG) coral reef records from islands belonging to French Polynesia (Anaa, Niau, Makatea, Moruroa, Takapoto, Bora Bora), the Hawaiian Islands (Oahu, Lanai, Midway Atoll), Tuvalu, Kiribati (Christmas Island, Tarawa), the Cook Islands (Mangaia, Atiu, Mitiaro, Mauke, Pukapuka, Rakahanga, Rarotonga), Tonga, Samoa, the Federal States of Micronesia, the Mariana Islands, the Marshall Islands (Enewetak, Bikini), New Caledonia, Papua New Guinea, the Solomon Islands, Vanuatu, Fiji and Niue. Studies reporting other sea-level indicators dated to other Pleistocene interglacials and Holocene sea-level indicators were not inserted in the database but are included in this data description paper for completeness. Overall, about 300 studies concerning Pleistocene and Holocene sea-level indicators have been reviewed, and finally 163 age data points and 94 relative sea-level (RSL) data points from 38 studies on the MIS 5e have been inserted in the database. An additional 155 age data points have been reviewed; i.e. the tropical Pacific islands database contains 318 age data points. The main sea-level indicators include emerged coral reef terraces, but also reef units recovered in drill cores from a few islands, thus reflecting the diversity of tectonic settings and sampling approaches. Future research should be directed towards better constrained RSL reconstructions, including more precise chronological data, more accurate elevation measurements and a better refinement of the palaeo-water-depth significance of coralgal assemblages. The database for tropical Pacific islands is available open access at this link: 10.5281/zenodo.3991672 (Hallmann and Camoin, 2020).
... The volume of 2018 lava that was deposited in the ocean is more than half of the total erupted volume. This partitioning of subaerial to submarine lava is similar to estimates from the 1868 Mauna Loa eruption (Stearns and Macdonald 1946) as well as the 1840 Kīlauea eruption and illustrates the importance of the combined subaerial and submarine records in fully understanding an eruption. Knowing the total volume of erupted lava for modern eruptions of Kīlauea is particularly important in order to link monitoring data (e.g., deformation, seismic, gravity, gas) to eruption processes. ...
Article
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Hawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.
... He considered that all the Hawaiian volcanoes formed simultaneously. Other early workers suggested the Hawaiian chain developed from a linear fracture propagating from west to east (e.g., Stearns, 1946;Eaton and Murata, 1960). Since there is no plate boundary at the location of the H-E chain, Wilson (1963) proposed that it formed as the Pacific plate moves over a relatively stationary magma source. ...
Article
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The Hawaiian-Emperor volcanic chain (H-E chain) is located in the middle of the North Pacific Ocean. It extends from northwest to southeast, including two segments, the older Emperor chain and the younger Hawaiian chain between which is a 60o change in strike, here termed the H-E bend. The H-E chain is the clearest and most intensively researched hot spot track in terms of plate motion, mantle plumes, tectonics, geochemical evolution, and lithospheric studies. However, debates on the formation of the H-E chain, in particular the H-E bend, concerning its origin in hot spot drift and/or Pacific plate motion change, have been ongoing for several decades. In this paper, we review current understanding and ideas concerning this debate and suggest ways forward. So far, neither hot spot southerly drift nor Pacific plate motion change can perfectly account for the geometry and progression of the H-E chain. In this review, we put forward a joint model where these two competing processes together can reasonably explain the evolution of the H-E chain and the H-E bend. In addition, we proposed three stages for formation of the H-E chain, including: 1) A ridge-plume interaction stage: Meiji~Detroit seamounts and a possible subducted section; 2) A combination of hot spot-Pacific plate motion: South of Detroit seamount ~ H-E bend; and 3) Pacific plate motion with a fixed hot spot: Hawaiian volcanic chain. In addition, any plate movement at the surface must be balanced by motion deeper in the mantle. Therefore, we consider that the surface Pacific plate motion and the state of deep mantle plume at 47–55 Ma are not totally separated but co-evolved. Furthermore, reconstructions of the Pacific plate and its boundaries should be considered if Hawaiian hot spot motion makes great contributions to the formation of the H-E chain. Nevertheless, establishing the causal links between these events and their underlying dynamic triggers requires further, more comprehensive work.
... Stearns (1935a, b, c) has been the first who studied Pleistocene shorelines on the islands of Oahu and Maui describing benches at elevations of +6 to +10.7 m and have been related to the Late Pleistocene . Beach deposits on Ulupau Head, Oahu, 900 occur up to 10.7 to 12.2 m above present sea level (Stearns, 1935c;Wentworth and Hoffmeister, 1939). ...
Preprint
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Marine isotope stage 5 deposits have been reported on many tropical Pacific islands. This paper presents a database compiled through the review of MIS 5e (Last Interglacial – LIG) coral reef records from islands belonging to French Polynesia (Anaa, Niau, Makatea, Moruroa, Takapoto, Bora Bora), the Hawaiian Islands (Oahu, Lana'i, Midway Atoll), Tuvalu, Kiribati (Christmas Island, Tarawa), the Cook Islands (Mangaia, Atiu, Mitiaro, Mauke, Pukapuka, Rakahanga, Rarotonga), Tonga, Samoa, the Federal States of Micronesia, the Mariana Islands, the Marshall Islands (Enewetak, Bikini), New Caledonia, Papua New Guinea, Vanuatu, Fiji and Niue. Studies reporting other sea-level indicators dated to other Pleistocene interglacials and Holocene sea-level indicators were not inserted in the database, but are included in this data description paper for completeness. Overall, about 300 studies concerning Pleistocene and Holocene sea-level indicators have been reviewed, and finally 284 data points from 35 studies on the MIS 5e have been inserted in the database. The main sea-level indicators include emerged coral reef terraces, but also reef units recovered in drill cores from a few islands, thus reflecting the diversity of tectonic settings and sampling approaches. Future research should be directed towards better constrained relative sea-level (RSL) reconstructions, including more precise chronological data, more accurate elevation measurements as well as a better refinement of the palaeo-water depth significance of coralgal assemblages. The database for Tropical Pacific Islands is available open-access at this link: http://doi.org/10.5281/zenodo.3991672 (Hallmann and Camoin, 2020).
... Soil is of typical basaltic origin derived from the original shied-building Wailuku Volcanic Series (Stearns and MacDonald 1942) with average annual rainfall approximately 3000 mm. (Giambelluca et al. 1986). ...
Article
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Cyanea heluensis H. Oppenheimer, sp. nov ., a new, narrowly distributed endemic species, is herein described and illustrated with line drawings and digital field photos. It is currently known from a single mature plant and is restricted to the upper Helu planeze on leeward Mauna Kahalawai, West Maui, Hawaiian Islands. It differs from all other species of Cyanea Gaudich. with its narrow, shallowly lobed leaves, gently curved muricate corollas, and undulate sepals caducous in fruit. A key to the new species and its congeners on Mauna Kahalawai is provided. Its conservation status and efforts to propagate the species are discussed.
... Stearns (1935a, b, c) was the first to study Pleistocene shorelines on the islands of Oahu and Maui, describing benches at elevations of +6 to +10.7 m related to the Late Pleistocene . Beach deposits on Ulupau Head, Oahu, occur up to 10.7 to 12.2 m above present sea level (Stearns, 1935c;Wentworth and Hoffmeister, 1939). ...
... But actual tubes are not the only features that might imply underlying tubal structures. Any volcano that is anything like circular in plan view is a good candidate for inferring that it is overlying feeding tubes such as are to be found represented as stocks and bosses in such places as those to be found in various valleys of the dissected volcanoes of West Maui, Hawaii (Stearns, H. T., 1942). Not all tubes contain crystalline complexes, either, as is well known to tourists who have seen the Thurston lava tube on Hawai'i Island <http://tinyurl.com/jhzvyu7>. ...
Research
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After having closely studied various topological patterns displayed by refractive indices (RIs) of a gabbroic rock sample from Ukumehame Gulch, West Maui, Hawai'i; I sought widely for similar patterns in natural landscapes. I became particularly interested in what I saw to be various tubular structures, coming to believe, for instance, that some "spheroidal weathering" might be tubular, extending beneath and along some surfaces.
... Olivine-rich sand was collected by M.B. Baker from Papakolea Beach (Pu'u Mahana), ~3 miles northeast of South Point, Hawaii (18°56'N, 155°38'W). The sands are remnants of 28 kyr wave-eroded olivine basalt flows and ash beds (Rubin et al., 1987), interpreted to be either a littoral cone (Stearns & Macdonald, 1947) or a primary ash vent (Walker, 1992) on the southern flank of Mauna Loa. Olivine grains 1-3 mm in largest dimension containing roughly spherical, glassy melt inclusions were separated from beach Accepted Article ©2020 American Geophysical Union. ...
Article
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Controlled cooling‐rate experiments were conducted on olivine‐hosted melt inclusions to characterize the development of compositional zoning observed in natural inclusions. All of the experimentally cooled inclusions are zoned due to olivine crystallization on the inclusion wall and diffusive exchange between the boundary layer adjacent to the growing olivine and the inclusion centers. Experimentally cooled inclusions are characterized by lower MgO and FeO, and higher SiO₂, Al₂O₃, Na₂O (and other incompatible oxides) near the inclusion wall relative to the inclusion center. The compositions at the centers of inclusions are susceptible to modification by diffusion, particularly for small inclusions and those subjected to low cooling rates. Uphill diffusion is evident in every oxide and is recognized by local extrema along a diffusion profile. CaO exhibits the most extreme manifestation of uphill diffusion, and a model attributes the diffusion behavior in CaO to solution nonideality in the boundary layer liquid. MgO profiles from experimentally cooled inclusions were fit with a diffusion model by varying the cooling rate. The cooling rate which resulted in the best‐fit was always within a factor of two and typically within ±10% of the experimental cooling rates, which ranged from 70–50,000 °C/hr. The model was applied to MgO profiles across natural glassy olivine‐hosted melt inclusions from Hawaii and the shergottite Yamato 980459. Cooling rates from zoned melt inclusions in Yamato 980459 range from 85–1047 °C/hr (mean = 383±43 °C/hr, 1σ, n=8), and support the hypothesis that the sample erupted at or near the Martian surface.
... That "not favored" idea follows the suggestion of Eakins and Robinson (2006) that the shoreline segment steps may represent the successive waning of volcanism to the distal ends of the East Maui rift zone: namely, that "subaerial flows continue to build the shield close to the summit while distal shorelines subside." By this alternative explanation, that SB#6 steps shallower than SB#6α would also require that supply to the east rift zone of East Maui waned before supply to its north and west rift zones, which we also consider less likely-noting that it is the north rift that has been barely (if at all) active in postshield times relative to the east and west rifts (Stearns & Macdonald, 1942). ...
Article
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Slope gradient maps of swath bathymetry around the Hawaiian islands locate 12 shield slope breaks associated with former shorelines that are now submerged, ranging in age back to 5 Ma. The age of their drowning correlates with the waning of tholeiitic shield volcanism that ceases to repave the shoreline sometime between the beginning and the end of the late‐shield stage. Slope breaks on Mauna Loa's northeast and southwest rifts are consistent with it being in the waning stages of shield building. Superposition of shorebreaks shows that the Hualālai shield is older than Mauna Kea's. We find evidence for three volcanic shields forming Ka'ena Ridge, for a simultaneous waning of Maui‐Lāna'i‐Kaho'olawe shield building and the initiation of Kohala shield building by 1.3 Ma, and for Mahukona growing to just above sea level about 0.6 Ma. A contiguous shoreline slope break formed ~1.8 Ma at the end of the West Moloka'i late‐shield stage and the beginning of the East Moloka'i late‐shield stage. At its western end the shield dips obliquely away from, rather than toward, this slope break. Similarly, the short Hualālai slope break plunges north, which is opposite to that expected for volcanic loading to the south. Shields locally sloping away from paleoshorelines may be related to landslides causing flexural back tilting away from their unloaded footwall. The Nu'uanu and Wailau slides and Pololū slump were mostly shield flank events that cut marginally into their former shorelines, enough to preferentially nucleate headward erosion by streams.
... Layer IV, a 60-cm thick pre-contact deposit, was particularly rich in lithic artefacts, fishing gear and faunal remains, and was associated with foundations from several round-ended houses defined by stone curbing and postmoulds, earth ovens and other domestic features. Stearns and Macdonald (1947), showing island lithic assemblages relative to the Hālawa Dune Site. ...
Article
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We analysed 1593 basalt artefacts from the Hālawa Dune Site, on the easternmost part of Molokaʻi Island, for a combination of geochemical and technological attributes to expose different reduction strategies related to basalt adze production and rejuvenation. West Molokaʻi is well known as a location where many outcrops were quarried to make adzes, but the island's east side has not been widely perceived as a location where adzes were produced in significant quantities in the prehistoric economy. We infer, however, through large‐scale geochemical non‐destructive energy‐dispersive X‐ray fluorescence (EDXRF) analyses, combined with technological analyses, that the majority of adzes at the Hālawa Dune Site were manufactured from local resources, supporting a predominantly localised pattern of adze production and use. Approximately one third of the adze debitage clearly related to use and rejuvenation (DA) is made from non‐local sources, but does not represent a heavy reliance on the full range of quarries on West Molokaʻi, and may also include samples derived from other islands or archipelagos.
... The recent geological history of the Maui-complex suggests that the imposition of geographic barriers has been the responsible factor. The islands of Maui and Molokai are now effectively separated by a shallow ocean channel, but at one or more times during the Pleistocene they must have been joined via a land connection (Stearns and Macdonald, 1942). At such times, populations of planitibia on the two islands would probably have been in genetic contact, if not completely coextensive, by virtue of the broader distribution of forest which would have been associated with the cooler and wetter glacial climates (Stearns, 1966). ...
... Coll Carbonaceous ash from top of the lower bed of Pahala ash exposed on SE end of seaward-facing Kaone fault scarp (19° 20' N Lat,155° 20' W Long), S slope of Kilauea Volcano, Hawaii. Section (Stearns and Macdonald, 1946) consists of 26 ft of upper part of Pa'hala ash, overlying 5 ft of pahoehoe basalt, 7 ft of lower part of Pahala ash and basalt. Carbon came from contact of lower part of Pahala ash with overlying pahoehoe. ...
Article
Dates in this list have been determined at U. S. Geological Survey radiocarbon laboratory, Washington, since our 1960 date list (USGS V). Procedures for the preparation of acetylene gas used in the counting, and the method of counting, (two days in two separate counters) remain unchanged. However, the modern standard used is no longer wood grown in the 19th century, but 95% of the activity of NBS oxalic-acid radiocarbon standard, as recommended at the 1959 Groningen Radiocarbon Conference. Measurement of the oxalic-acid standard at our laboratory indicates 6.2 ± 1% more C 14 activity than our modern wood standard; so use of the new standard should make no appreciable difference when comparing samples computed by the old method. W. F. Libby's (1955) half-life average for C 14 , 5568 ± 30 years, was used for the decay equation.
... (Porter, 1979), so the present elevation of the site probably marks the lowest point in its history. The water table in the study area is located near sea level due to the high permeability of the island's volcanic rocks (Stearns and MacDonald, 1946;Takasaki, 1978). ...
Article
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We document stoichiometric dolomite occurring in a nonsaline Quaternary soil on the Kohala peninsula, northwestern Hawaii. Geologic constraints and geochemical and isotopic data confirm that this dolomite is not the result of marine influence or wind-blown dust. The strontium isotopic composition of the dolomite (87Sr/87Sr = 0.7045–0.7048) is indicative of its derivation primarily from the weathering of basaltic parent material rather than from meteoric water or seawater. Infiltration of soil waters with elevated Mg/Ca (>1) derived from alteration of ferromagnesian minerals such as olivine likely led to dolomitization of early-precipitated soil calcite and/or to direct dolomite precipitation in the profile. This demonstrates that well-ordered dolomite can form in a nonmarine environment at temperatures <100 °C without undergoing burial diagenesis.
... This altitudinal trend in prevalence is attributed partly to climatic constraints (i.e., ambient temperature, humidity, rainfall) imposed on vector reproduction and survival, and parasite development (LaPointe 2000; Ahumada et al. 2004;LaPointe et al. 2010). In addition to the altitudinal gradient across the Kahuku-Ka'u landscape, there is a dramatic rainfall gradient that peaks at mid-elevation due to the orographic effects of the Ninole Volcanic Series (Stearns and MacDonald 1946) located just to the south of Maka'alia. This makes the steep slopes of Ka'u an area of higher moisture where more larval mosquito habitat is available at temperatures favorable for vector development (Figure 2). ...
Technical Report
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While avian disease has been well-studied in windward forests of Hawai‘i Island, there have been few studies in leeward Ka‘u. We surveyed four altitudinal sites ranging from 1,200 to 2,200 m asl in the Kahuku Unit of Hawai‘i Volcanoes National Park (Kahuku) and three altitudinal sites ranging from 1,200 to 1,500 m asl in the Ka‘u Forest Reserve (Ka‘u) for the prevalence of avian disease and presence of mosquitoes. We collected blood samples from native and non-native forest birds and screened for avian malaria (Plasmodium relictum) using PCR diagnostics. We examined birds for signs of avian pox (Avipoxvirus sp.), knemidokoptic mange (Knemidokoptes jamaicensis) and feather ectoparasites. We also trapped adult mosquitoes (Culex quinquefasciatus and Aedes japonicus japonicus) and surveyed for available larval habitat. Between September, 2012 and October, 2014, we completed 3,219 hours of mist-netting in Kahuku capturing 515 forest birds and 3,103 hours of mist-netting in Ka‘u capturing 270 forest birds. We screened 750 blood samples for avian malaria. Prevalence of avian malaria in all species was higher in Ka‘u than Kahuku when all sites were combined for each tract. Prevalence of avian malaria in resident Hawai‘i ‘amakihi (Chlorodrepanis virens) was greatest at the lowest elevation sites in Kahuku (26%; 1,201 m asl) and Ka‘u (42%; 1,178 m asl) and in general, prevalence decreased with increasing elevation and geographically from east to west. Significantly higher prevalence was seen in Ka‘u at comparable low and mid elevation sites but not at comparable high elevation sites. The overall presumptive pox prevalence was 1.7% (13/785) for both tracts, and it was higher in native birds than non-native birds, but it was not significant. Presumptive knemidokoptic mange was detected at two sites in lower elevation Kahuku, with prevalence ranging from 2‒4%. The overall prevalence of ectoparasites (Analges and Proctophyllodes spp.) was 6.7% (53/785). The site with the highest prevalence was Lower Glover in Kahuku (7.2%; 10/138) and Maka‘alia in Ka‘u. In general, mosquito larval habitat was more prevalent at lower elevation sites than higher elevation sites within the Kahuku—Ka‘u landscape, and more prevalent in Ka‘u than Kahuku. We observed significantly more available larval mosquito habitat in total belt transect plots in Ka‘u than Kahuku for both hapu‘u cavities (Χ2 = 47.06, df = 1, p < 0.01) and other habitat types combined (i.e., ground pools, rock holes, tree holes) (Χ2 = 104.35, df = 1, p < 0.01). Mosquitoes were most abundant at low elevation Kahuku, but were captured at all sites up to 1,532 m asl in Kahuku. The malarial infection rate of live mosquitoes was 21% (39/186) at Kahuku and 25% (2/8) at Ka‘u. There were 19 times more larval habitats available in Ka‘u than Kahuku on survey transects, yet we captured 53 times more C. quinquefasciatus mosquitoes in Kahuku. We captured very few adult A. j. japonicus across the landscape (Ntotal = 6) and no Aedes albopictus were detected in this study. Larval surveys along ranch roads and infrastructure revealed that ground pools along rutted, overgrown ranch roads were the likely source of Kahuku mosquitoes. We did not find mosquito larvae associated with ranching infrastructure. Unlike the low elevation forests on windward Hawai‘i Island, avian malaria prevalence, mosquito abundance, and the density of available larval habitat in Kahuku and Ka‘u were relatively low. Although altitudinal variations in climate appear to be the primary factors limiting the distribution of avian disease, habitat type, avian movements, human activity, and feral pig (Sus scrofa) management all may play important roles in determining the prevalence of avian malaria across the Kahuku—Ka‘u landscape.
... There is also evidence for fresh water in a second, shallower zone in the Mauna Loa section (Fig. 8). The picture that emerges at the HSDP site of alternating intervals of fresh and salt water saturation in the nearshore environment and of freshwater transport beneath saline water contrasts with widely applied models of Hawaii's hydrology, which have changed little since they were introduced by Stearns and Macdonald (1946). ...
Article
Petrological, geochemical, geomagnetic, and volcanological characterization of the recovered core from a 1056-m-deep well into the flank of the Mauna Kea volcano in Hilo, Hawaii, and downhole logging and fluid sampling have provided a unique view of the evolution and internal structure of a major oceanic volcano unavailable from surface exposures. Core recovery was ∼90%, yielding a time series of fresh, subaerial lavas extending back to ∼400 ka. Results of this 1993 project provide a basis for a more ambitious project to core drill a well 4.5 km deep in a nearby location with the goal of recovering an extended, high-density stratigraphic sequence of lavas.
... The island belongs to the former "Maui Nui" group of subaerially continuous volcanoes including Lanai, Kahoolawe and Molokai, and is composed of two overlapping volcanoes: Mauna Kahalawai, the older West Maui volcano, and Haleakala, the younger East Maui volcano. Three lava units compose Haleakala volcano: (1) tholeitiic and alkali basalts from the late shield building stage (Honomanu > 0.96 Ma), (2) alkalic basalts, hawaiites, mugearites and ankaramites from an early postshield stage (Kula, and (3) ankaramites, alkalic basalts and hawaiites from a stratigraphically distinct later postshield stage (Hana ≤ 0.12 Ma; Clague and Sherrod 2014; Macdonald et al. 1983;Macdonald and Katsura 1964;Naughton et al. 1980;Sherrod et al. 2006;Stearns and Macdonald 1942). Recent K-Ar age dating indicates that the Haleakala produced ca. 15 eruptive sequences in the past 1500 years (Sherrod et al. 2003). ...
Article
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Magma storage depth is a fundamental aspect of a volcano’s magmatic plumbing system that may be resolved using mineral-melt thermobarometry, assuming crystal growth occurs at near-equilibrium conditions. We acquire major and minor element compositional analyses of whole rock, groundmass separates, and clinopyroxene in ankaramite erupted ca. 214 ka at Haleakala volcano to evaluate the efficacy of thermobarometry. Using various thermometer and barometer combinations, we obtain values of crystallization pressure (60–1500 MPa) that are generally consistent with those of previous studies, but find that the models most successful at recovering the conditions of relevant equilibrium experiments yield values at the low end of this range (≤950 MPa). We use quantitative EPMA spot analyses to transform X-ray element intensity maps into metal oxide concentrations maps and to produce qualitative pressure maps of whole crystals. The spatial context provided by this procedure reveals two compositionally distinct domain types not evident in the spot analysis data set, with median Na2O contents differing by up to 26 % between domains. Na-rich domains represent putative crystallization pressures that are up to 365 MPa higher than Na-poor domains, within individual crystals. The presence of Na-rich domains associated with euhedral facets in contact with matrix is not consistent with concentric growth at near-equilibrium conditions of decreasing pressure, but rather co-crystallization of both domains under conditions of partial disequilibrium. Conservatively assuming that low-Na regions are less prone to kinetic partitioning, crystallization pressures for the Haleakala ankaramite correspond to crustal levels. We conclude that the reservoir supplying postshield eruptions at Haleakala has not deepened into the mantle, as was reported in a previous application of clinopyroxene thermobarometry to Haleakala’s postshield magma (Chatterjee et al. 2005).
... Euhedral crystals of clinopyroxene in ankaramite lavas and pyroclastic materials erupted during the postshield stage of Haleakala volcano, Hawaii, figure prominently in formative studies of the volcano (Cross 1915;Daly 1911;Washington and Mervin 1922) as hallmarks of alkalic basalt magmatism and as exemplars of the monoclinic 2/m crystal point group. Their morphologic near-perfection ( Fig. 1) coupled with relatively restricted major element compositional variation (Fodor et al. 1975) supports the interpretation that these are slowly grown crystals, incubated in the subvolcanic magma reservoir over long timescales at conditions at low supersaturation (Stearns and Macdonald 1942). The assumption of chemical equilibrium underpins applications of clinopyroxene-melt thermobarometry to constrain the temperature and pressure in the reservoir prior to magma ascent (Chatterjee et al. 2005). ...
Article
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We investigated the external morphologies and internal compositional zoning patterns of clinopyroxene phenocrysts in an ankaramite of Haleakala volcano (Hawaii) to constrain magma crystallization conditions in the volcano’s postshield stage. The phenocrysts are characterized by euhedral faceted morphologies and crystallographically coherent subcrystals. Quantitative EPMA and X-ray element mapping reveal two domains within the crystals: porous, Si–Mg–Ca–Cr-rich zones associated with the forms {100}, {010} and {110}, and nonporous, Al–Ti–Na-rich zones associated with the forms {−111}. The chemical variations, internal porosity and parallel subcrystals are consistent with nonconcentric crystal growth at varying degrees of supersaturation. We infer that initial growth occurred in a diffusion-limited regime to produce dendritic crystals; subsequent growth was markedly slower, with lesser supersaturation allowing dendrites to infill and produce polyhedral external morphologies. This sequence promoted the evolution of crystals from an hourglass shape with dominant {−111} forms, to sector-zoned euhedral crystals in which elements were partitioned according to: (Al + Ti + Na){−111} = (Si + Mg + Cr + Ca){110},{100},{010}. Infilling of dendritic crystals occurred to a greater extent on faster-growing sectors and was interrupted by the eruption, resulting in porosity of the slower growing {hk0} sectors. Outermost Na-poor rims formed on all sectors due to slower growth rate under interface-limited conditions. Paradoxically, high levels of supersaturation producing large crystals of clinopyroxene (and olivine) are indicated in the volcano’s deep-seated reservoir and lower degrees of supersaturation characterize syneruptive crystal growth. The presence of vapor bubbles within the melt-filled crystal embayments and inclusions suggests rapid clinopyroxene growth caused volatile saturation and reservoir pressurization, leading to eruption of the ankaramite.
... The Kaupō fan lavas date to the post-shield building phase of Haleakalā Volcano (Stearns and MacDonald, 1942;Sherrod et al., 2007). These Hana Volcanic Series lavas overlie older, shield-building phase Kula Volcanic Series land surfaces, which persist only on the eastern and western margins of Kaupō. ...
Article
Rain-fed, intensive field systems based on sweet potato and to a lesser extent dryland taro were essential to the political economies of emergent archaic states in late pre-contact Hawai'i. The productivity of these dryland field systems was dependent upon soil nutrient pools that are constrained primarily by geological substrate age and rainfall. We investigated soil nutrient properties across the Kaupō fan, locus of the largest intensive field system on eastern Maui Island. Thirty-six soil samples were obtained along three rough transects, and analyzed for exchangeable bases (calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), base saturation, pH, androck content). Although some variation in soil properties is evident across the Kaupō fan, in aggregate the samples exhibit high levels of base saturation and exchangeable Ca, indicating good potential for sustained, intensive cultivation. When compared with the Leeward Kohala Field Systemon Hawai'i Island, the Kaupō field system waslikely to have been even more productive based on the relative soil nutrient pools. The high productive capacityof the Kaupō field system is likely to have played a key role in the decision of the early 18th century Maui King Kekaulike to move the island's royal center to Kaupō.
... Coll Carbonaceous ash from top of the lower bed of Pahala ash exposed on SE end of seaward-facing Kaone fault scarp (19° 20' N Lat,155° 20' W Long), S slope of Kilauea Volcano, Hawaii. Section (Stearns and Macdonald, 1946) consists of 26 ft of upper part of Pa'hala ash, overlying 5 ft of pahoehoe basalt, 7 ft of lower part of Pahala ash and basalt. Carbon came from contact of lower part of Pahala ash with overlying pahoehoe. ...
Article
Laterite weathering profile (LWP) thicknesses are functions of precipitation rate and time, but their exact dependence on them is uncertain. We investigate LWP development on ground surfaces in Hawai'i that are neither aggrading nor eroding across substrates from 0.01 to 4 Ma and rainfall rates of <250 to >3000 mm/a. The Hawaiian Islands provide an excellent opportunity for LWP studies across climates and over millions of years on a single rock type, basalt. LWP weathering rates are usually determined by geochemical approaches. We present a geophysical method once bedrock ages and precipitation rates are known. We employed multichannel analysis of surface waves and horizontal‐to‐vertical spectral ratio methods. Results indicate that >70% of the variability in LWP thickness is due to precipitation and bedrock age. The remainder is attributed to measurement uncertainty and heterogeneity in the permeability of basalt. LWPs develop by two paths. Dry (<1000 mm/a) areas have a negative water balance with evapotranspiration exceeding rainfall. LWPs thicken until they reach a steady state where the storage capacity of the saprolite precludes the percolation of water into subjacent lava. In wetter areas, downslope interflow produces thick laterite wedges near coastlines that migrate upslope over ~1 Ma. Subsequently, they thicken and reach a steady state where precipitation cannot deliver water through the vadose zone. LWPs' thickness ( T ) increases as a function of time ( t ) and precipitation ( P ) according to the expression (95% confidence): . The first partial derivative, or weathering rate, is . Weathering rates decrease with time and are strong functions of t and P . These expressions add considerable insight into the rates and processes driving weathering at large scales and can also be solved for t , giving a rough estimate of the time of landscape formation of eroded surfaces.
Article
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In order to understand further the emplacement (i.e., volcanic growth) of 22 Icelandite and 3 Rhyodacite cooling units in one of the long volcanic sequences known as Mauna Kuwale of the Wai’anae volcano (ca. 3.3 Ma), Oahu Hawaii we have conducted appropriate rock magnetic experiments described below as well as anisotropy of magnetic susceptibility (AMS) studies of such 25 units. We have undertaken rock magnetic investigations such as continuous and partial thermo-magnetic cycles of low field magnetic susceptibility versus temperature dependence, (k-T) curves experiments. We classified the k-T heating-cooling dependence of susceptibility in three groups A, B and C. Type A: yielded two components of titano-magnetite with a predominat Ti rich phase and occasionally a relevant magnetite component phase. Type B: samples are characterized by Ti poor magnetites. Magnetite dominates as the main magnetic carrier. Type C: k-T curves show one single phase of titanomagnetite, and Ti poor magnetite. The coercivity or remanence, determined by back field magnetization is always
Article
The geologically complex western aquifers of Hawai‘i Island serve as the primary reservoir of fresh potable water for residents, yet the area’s hydrogeologic characteristics are still not well understood. Groundwater age is a fundamental parameter used to better understand groundwater flow and storage, yet few studies have attempted to estimate apparent groundwater ages in Hawai‘i. This study implements a multi-tracer approach using chlorofluorocarbons, sulfur hexafluoride, and tritium to determine the apparent ages of young water masses from the West Hawai‘i aquifers. Chlorofluorocarbon and tritium tracer measurements suggest that the aquifers contain young groundwater with a median age of 53 years, but that a significant volume of older groundwater exists, which was recharged prior to the release of these anthropogenic tracers. Mixing models suggest that the groundwater consists of mixtures with an average 28% modern water (<70 years), with the remainder being recharged prior to 1953. Further, helium measurements demonstrate that the area’s groundwater is influenced by hydrothermal and magmatic processes from Hualālai volcano, which bias estimated groundwater ages if not properly considered. It is therefore beneficial to utilize a multi-tracer approach in an oceanic volcanic island setting, where groundwater ages are impacted by various external processes. The analysis of young apparent ages and proportions can aid in coastal aquifer characterization and subsequent groundwater quality assessment and is crucial for sustainable groundwater management.
Article
Seismic methods, electrical resistivity, and outcrop observations provide an integrated subsurface view of young basaltic lavas and their overlying weathered products. The study site is a sea cliff in the Kohala province in the northwestern part of the Big Island of Hawai'i, which provides an ideal laboratory for combined seismic reflectivity, shear-wave velocity, electrical resistivity, and outcrop observations. Our primary observation is the division of the shallow subsurface into weathered (saprolite) and underlying unweathered (hard basalt) zones. Significant heterogeneity is evinced by strong reflectivity changes within and between the two zones and the structural variability of the basal surface separating the weathered zone from the unweathered zone (reflector undulations, fault offsets, and prominent diffractions). Seismic reflectivity contrasts arise from variations in rigidity and porosity (density) corresponding to seaward-dipping lava flow units. The degree of clay alteration is interpreted to govern subsurface resistivity variations along with the influence of fresh groundwater and the incursion of seawater saturating the porosity. Our study provides a generalized model for visualizing weathered versus unweathered basaltic lavas in the shallow subsurface.
Article
Over an approximately 1,000-year settlement history, the distribution of Native Hawaiian cultural sites across the landscape has been driven, in large part, by environmental factors. Through an exploration of the precontact ritual, residential, and agricultural sites of Kaupō, Maui, the ways soil nutrients and arable land resulted in discrete zones of production and power can be seen. With the arrival of American and British missionaries in the mid-1800s, however, these environmental influences carried forward in the differential selection of Hawaiian temple sites to be destroyed and rebuilt as Christian churches. As a result, Kaupō’s two churches (which remain functional today) can be best understood as a result of long-term ecological processes often overlooked in historical archaeology today.
Conference Paper
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On October 15, 2006, two earthquakes with magnitudes of 6.7 and 6.0 struck in close succession just off the northwest coast of the Island of Hawai’i. Damage caused by the earthquakes has exceeded $100 million; however no deaths and only minor injuries were reported. Numerous rockfalls and landslides occurred in road cuts, embankments and natural slopes. Because of the lack of redundancy in the highway systems of the islands, road closures due to rockfalls or landslides can have debilitating effects on the transportation systems. Most rockfall and landslide events occurred on the Big Island, and on the southwest coast of Maui. The Hawai’i Department of Transportation (HIDOT) is implementing a program of rock slope stabilization throughout the islands, including placement of rockfall drapes on the steep rock slopes along Route 30 on the south side of the western end of Maui (which did not suffer damage from the earthquakes). HIDOT implemented these programs long before the October 15, 2006 earthquakes. As part of on-going slope stabilization, the department elected to stabilize the rock slopes above the portals to the Pali Tunnel, located at Milepost 10.4 on Route 30. This two-lane paved roadway can have ADT counts up to 60,000 vehicles per day, as the roadway provides the most direct route for tourists from the Kahului Airport to the resorts in Lahaina, located on the western side of Maui. The roadway also serves as the primary route for emergency and commercial vehicles serving the resort areas. Therefore, HIDOT limited traffic stoppages for rock slope mitigation construction to 20 minutes, and these could only occur during the night. Differential weathering typical of young volcanic rocks, coupled with precipitation events and ground motions induced by earthquakes, are the principal causes of rockfalls in Hawai’i. The bedrock at the tunnel consists of thin to medium bedded Wailuku basalt flows, separated by thin to medium bedded, discontinuous beds of clinker and scoria, and thin beds of lateritic soils. Initial construction of the Pali Tunnel in 1951 did not include stabilization of the slopes above the portals, as these were fresh cuts at the time of construction. Weathering has diminished the stability of the slopes above both portals, which required light scaling prior to placement of rockfall drapes. However, the slopes above the west portal rise thousands of feet to the north, and contain large, loose boulders on the verge of toppling and rolling onto the high-way. To reduce maintenance associated with preventing rockfalls from reaching the roadway, HIDOT selected an innovative, commercially-developed hybrid rockfall barrier/drape to contain rolling rocks from high on the slope. The hybrid contains elements of a 2,000 kJ rockfall barrier, with ring nets extended as a drape below the barrier. To protect traffic while construction of the hybrid was underway, a lower 1,000 kJ rockfall barrier was constructed on a lower portion of the slope. Hybrid systems have recently been implemented in Washington, California, New Jersey and Colorado, and are undergoing field testing in Italy.
Thesis
The amphitheater headwalls of some bedrock canyons have been used to infer the environmental conditions and erosion processes responsible for shaping the surfaces of Earth and Mars. Morphologic identification of process is hampered, however, because we lack basic field observations and quantitative models of erosion and sediment-transport in bedrock canyons. Herein I describe five related efforts to identify erosion and transport processes through field observations and measurements of canyons on Earth, and to develop quantitative models for some of these processes. First, I present a compilation of new observations and those of others, and conclude that, despite assertions that amphitheater form is due to groundwater-seepage erosion, the evidence to support this hypothesis is ambiguous or nonexistent for most bedrock canyons. A detailed examination of two prominent examples, the Kohala valleys in Hawai‘i and Box Canyon in Idaho, has revealed no evidence for seepage erosion. Instead, field observations and topographic analyses of the Kohala valleys suggest that they likely formed by waterfall plunge-pool erosion following large-scale slumping of Kohala Volcano. In addition, sediment transport measurements and dating indicate that Box Canyon owes its origin to large-scale flooding that occurred about 45 thousand years ago. To better quantify erosion and transport processes, a mechanistic model is presented to predict the conditions under which coarse sediment is mobilized in rivers and streams over a wide range of channel-bed slopes. Lastly, I present a model for abrasion of bedrock riverbeds by impacting particles carried in bedload and suspended load.
Article
This list contains the results of measurements made during 1963 and 1964. Samples are counted in the form of acetylene gas, as previously, and ages computed using the Libby half-life of 5568 ± 30 yr. The error listed is always larger than the one-sigma statistical counting error commonly used, takes into account known uncertainty laboratory factors, but does not include external (field or atmospheric) variations.
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A well-preserved, vertically stacked succession of two genetically distinct eolianites and associated caliche paleosol units, capped by modern and Holocene coastal dunes, occurs at Kaiehu Point, west Molokai, Hawaii. The Pleistocene eolianite facies comprise well-cemented, medium grained skeletal carbonate sand and their morphostratigraphic context implies formation at times of lower than present sea level. Amino acid racemization (AAR) evidence suggests eolianite formation late in marine Oxygen Isotope Stage (OIS) 5, but lacks the precision to uniquely define in which isotopic substage the deposits formed. Coupled with the AAR results, the morphostratigraphic evidence, would suggest that the Lower Eolianite formed in OIS 5c and the Middle Eolianite during 5a with their superposed caliche paleosols having formed in subsequent stadial stages. The unconsolidated coastal sand dunes of Holocene age contain reworked Late Pleistocene skeletal carbonate sand based on AAR evidence. The most likely source of the reworked carbonate is from the erosion of the eolianites at Kaiehu Point. The Pleistocene eolianite-caliche paleosol sediments reveal variable Mg-content, stable isotope ratios and petrological characteristics consistent with changing degrees of weathering intensity and meteoric diagenesis. These changes are attributed to orographic effects resulting from relative sea-level changes. Accordingly, a two-phase model is favored for the formation of the eolianite-paleosol successions at Kaiehu Point, west Molokai. Eolianite sedimentation is initiated at times of marginally lower sea levels promoting the landward migration of bioclastic sand to form extensive eolian sandsheets. This is followed by a more pronounced phase of pedogenesis associated with a further fall in sea level and concomitant increased rainfall due to enhanced orographic effects.
Article
. The allozymic (allelic isozymic) variation encoded by fifteen loci was examined in sixteen species comprising the D. planitibia subgroup of the picture winged Hawaiian Drosophila . The level of heterozygosity within populations is highly variable but in general appears to be slightly lower than that found in continental species of Drosophila . Determinations of genetic similarities among species reveals a range of values from 0.11 to 0.99. A phenetic cluster of the matrix of similarity values reveals several distinct clusters. Within these subclusters most dissimilar species are those most likely to have been founded by small numbers of individuals. We interpret this to mean that the kind of founding event will directly affect the rate of allozymic differentiation. Thus, values of genetic similarity between species have limited phylogenetic significance unless supplemental evidence can define the kinds of founding and speciation events that have occurred during the evolution of a group of species.
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The conventional 14C ages of 8 marine shells of known age and 11 marine shells stratigraphically associated with dated wood charcoal show considerable variation from expected ages. One source of this variation is seashore geology; comparison of 6 AMS dates on 3 species of shallow-water, herbivorous gastropod shells from Pleistocene limestone and Holocene volcanic coasts shows that shells from Pleistocene limestone coasts can have apparent, or reservoir, 14C ages up to 620yr greater than shells of the same species from volcanic coasts. The relatively great variation in apparent ages of Hawaiian marine shells poses problems for their use in dating archaeological sites. For best results, an archaeological marine shell should be sourced to a particular local environment, and the apparent age of shells in that environment determined by dating well-provenienced shells of known age. -Author
Chapter
Many volcanic eruptions result from the interaction of magma and external water (Table 9-1), but few volcanologists (e.g., Jaggar, 1949) have emphasized the importance of nonmagmatic water in volcanic eruptions. In our view, the importance of external water in explosive eruptions is still underestimated. Wood (personal communication) even holds that maars, which most commonly develop from hydroclastic eruptions, are the second most common volcanic landform on earth next to scoria cones.
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