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Frank A. Trusdell

Publications and source records attributed to Frank A. Trusdell.

At least 19 recordsLinked to original sources
USGS2026

Timescales of cumulate mobilization and mixing for the 1868 A.D. eruption of Mauna Loa, Island of Hawai‘i

The deadly 1868 A.D. eruption of Mauna Loa’s lower Southwest Rift Zone (Island of Hawai‘i) included a M7.9 earthquake and associated tsunami and landslides, demonstrating the severe hazards posed by Earth’s largest active subaerial volcano. To better understand the relationship between intense seismic activity, dike emplacement, magma storage, transport histories, and mobilization of olivine cumulates at Mauna Loa, we examine compositional zoning of olivine in the 1868 lava flows. Samples range from basalt (< 10% olivine) to picrite (30–40% olivine). The olivine cargo is heterogeneous (Fo 78.2–89.2 ; forsterite = [Mg/(Mg + Fe) × 100]) but dominated by ~ Fo 89 cores that lie above the Fe-Mg equilibrium field of host glasses. Crystal rims < Fo 80 are due to post-eruptive modification in slow cooling lava flows. Minor element compositions fall within the range of other Mauna Loa olivine erupted in the past 200 years. Olivine crystals exhibit both normal and complex Fo zoning patterns that yield timescales of diffusive re-equilibration that range from 3 to 258 days, with 72% of crystals recording 71 days or less. These timescales correspond to magmatic priming of the summit reservoir system ~ 2 months prior to the eruption and the M7.9 earthquake likely facilitated the transport of the crystal-rich summit-derived magmas downrift shortly prior to eruption. If the recently proposed faster Fe-Mg diffusion coefficient is used, timescales instead range from < 1 day to 25 days, with most recording 1 week or less. In this scenario, most of the olivine zoning would have to have been generated after the M7.9 earthquake perturbed the system.

Hawaii↗
USGS2026

Geochemistry of the 2022 Mauna Loa eruption: A comparison with earlier historical summit reservoir eruptions, with implications for magma supply and recharge

On November 28th, 2022, following a record historical repose period of 38 years, Mauna Loa erupted about 145 × 10 6 m 3 of lava and tephra over a 15-day period. The eruption was confined to the summit caldera region and the upper Northeast Rift Zone and is remarkably homogeneous in composition in both time and space. In these respects, it is typical of prior shallow summit reservoir magma bodies, recently estimated to be at a depth of around 1–2 km beneath the caldera. In contrast with these earlier magma bodies, which typically contain 6.7–7.1% MgO and are perched at the low-MgO end of olivine-control trends, the 2022 lava and tephra are more evolved with 6.24 + / − 0.03% MgO. This implies a temperature difference of around 11 °C with the prior 1984 magma. The simplest explanation is that over 38 years, cooling and crystallization of the remaining 1984 magma body has significantly exceeded magma recharge, giving rise to the evolved 2022 magma. The problem with this model is that we know from a variety of geophysical observations that in those 38 years, Mauna Loa has been erratically inflating, with heightened periods since around 2000 attributed to magma recharge. To reconcile these differences, we suggest instead that the 1984 magma cooled and crystallized much more extensively, from 1166 °C to around 1106 °C, co-crystallizing plagioclase, clinopyroxene, pigeonite and subsequently enstatite instead of pigeonite. At this point, the residual 1984 magma would have an MgO content around 4.2% and been about 50% solidified. Subsequent recharge and mixing by dominantly reservoir magmas, derived from a deeper 3–4-km intermediate magma reservoir, eventually produced the 2022 magma.

Hawaii↗
USGS2026

Osmium isotope constraints on Mauna Loa–Kilauea magmatic connectivity, Island of Hawai‘i

The Hawaiian volcanic chain exhibits a long-recognized double track of volcanism defined by the Loa and Kea trends, which erupt chemically and isotopically distinct lavas. Mauna Loa and Kīlauea, the two most frequently active volcanoes of the Loa and Kea trends, produce distinct endmember compositions. However, historical periods of compositional convergence have prompted debate regarding a potential magmatic connection between the two adjacent volcanoes. Proposed links include a shallow edifice-level plumbing system, a common magma source at ∼40 km depth, or a deeper asthenospheric source. In the latter scenario, based on correlated Sr–Nd–Pb isotopes and trace-element systematics, a “shared” mantle source supplies melt alternately to both volcanoes on multi-decadal timescales. Here, we use Os isotopes to evaluate the proposed connections. We measured Os isotopes in eight historical Mauna Loa tholeiites along with three Kīlauea tholeiites (1832 summit eruption; Uēkahuna Bluff; 2000 Pu‘u‘ō‘ō eruption) previously identified as isotopically intermediate between Mauna Loa and Kīlauea endmembers. We found that the acidic bromide leachates of all samples yield more radiogenic 187 Os/ 188 Os than corresponding bulk residues, with the labile Os-bearing phase comprising ∼0.4–27% of bulk Os. Mauna Loa tholeiites display nearly constant 187 Os/ 188 Os over the past ∼200 years (0.134–0.136; mean = 0.1357 ± 0.0013, n = 8, 2SD), despite large variations in total [Os] ranging from ∼30 pg/g (2022 tholeiite) to ∼966 pg/g (1868 picrite). The Kīlauea 1832 sample has 187 Os/ 188 Os = 0.1302 ± 0.0008, slightly higher than the Kīlauea endmember (0.1285 ± 0.0008), whereas the Uēkahuna Bluff and Pu‘u‘ō‘ō samples exhibit more elevated ratios (0.1314 ± 0.0008 and 0.1327 ± 0.0008, respectively). We conclude that the “shared” mantle source exerts negligible control on Mauna Loa Os isotope systematics. In contrast, the Kīlauea mantle source is more heterogeneous, with contributions from small-scale recycled domains with variable time-integrated Re/Os ratios.

Hawaii↗
USGS2026

Lava flow emplacement dynamics during the Mauna Loa 2022 eruption

On November 27, 2022, Mauna Loa erupted for the first time in 38 years, threatening a major highway on the Island of Hawaiʻi. The opening phases of the eruption were focused at the volcano’s summit, before magma propagated into the upper Northeast Rift Zone to erupt at four fissure segments that localized at fissure 3 by December 2. This fissure produced a braided ʻaʻā flow that traversed the steep north flank at >1 km/hr, before slowing as slopes shallowed. Effusion rates peaked in the early hours of the eruption and then steadied at around 100 m3/s at fissure 3. Lava effusion became variable and dropped abruptly on December 7. The eruption ended on December 10 with a final flow length of 18 km. We tracked lava effusion rates, flow advance, channel dynamics, and 3-D flow field development with field and remote sensing observations throughout this eruption to inform lava flow forecasts and investigate ʻaʻā flow dynamics. Flows were mapped using optical and infrared imagery, uncrewed aircraft systems, and airborne single-pass InSAR. Video- and time-lapse cameras were deployed to record lava fountaining and channelized flow at frequent intervals, supplemented by field measurements. Analyses of these data built a detailed record of effusion rates and associated flow dynamics. We combine these high frequency observations of the proximal flow field with broader thermal and 3-D mapping of the evolution in the medial and distal flow field to examine ʻaʻā flow dynamics from source to toe. Within the steep, medial section of the flow field, channel blockages caused back-ups and overflows as the eruption progressed. Disrupted lava supply to the distal flow field and low slopes resulted in stalling, widening, and thickening at the toe. Overall, 142 million m3 of lava covered 36 km2 over 13 days. Our results inform the controls on development and evolution of lava flow fields, with implications for forecasting primary flow advance and secondary flow field growth.

Hawaii↗
USGS2026

Between quiescence and crisis: Hawaiian Volcano Observatory communication and response strategies on the Island of Hawaiʻi

Over the past two centuries, eruptions of Mauna Loa volcano have damaged infrastructure and destroyed several communities on the Island of Hawaiʻi. Future eruptions will impact existing population centers and critical infrastructure, which continue to grow each year. The U.S. Geological Survey Hawaiian Volcano Observatory has developed and practiced methods to promote eruption preparedness in communities on the Island of Hawaiʻi, particularly over the past three decades during which Mauna Loa was quiescent while Kīlauea volcano erupted frequently. Here, we summarize the observatory’s efforts to increase awareness of hazards associated with Hawaiian volcanoes and describe how lessons learned during responses to past volcanic crises on Kīlauea were applied prior to and during the 2022 Mauna Loa eruption, highlighting new response communication challenges encountered during the event. Additionally, we identify potential avenues for future communication/outreach on the Island of Hawaiʻi, such as expanding efforts in communities located in high-hazard areas and striving to be more culturally and linguistically inclusive in our communication techniques.

Hawaii↗
USGS2026

Geologic map of the Emmons Lake volcanic center, Alaska

Introduction The Emmons Lake volcanic center is a spatially clustered group of stratovolcanoes and calderas in the southwestern part of the Alaska Peninsula, Alaska. The volcanic center is characterized by several ice- and snow-clad stratovolcanoes located within and along the margins of a nested-caldera complex that includes Emmons Lake. A shieldlike ancestral edifice (ancestral Mount Emmons) is truncated by the caldera complex and forms a broad volcanic platform around the center. The main stratovolcanoes of the Emmons Lake volcanic center are Pavlof Sister, Pavlof Volcano, Little Pavlof, Double Crater, Mount Hague, and Mount Emmons. Several small unnamed cinder cones and vents also are located within Emmons Lake volcanic center and on the east flank of Pavlof Volcano. Many of these cones and vents have been the source of the young lava flows that mantle the floor of the caldera. Pavlof Volcano, in the northeastern part of the Emmons Lake volcanic center, is one of the most historically (that is, the past about 300 years) active volcanoes in Alaska, and eruptions from Pavlof Volcano pose the greatest hazards to the region. Volcanic rocks of the Emmons Lake volcanic center overlie continental and marine sedimentary rocks of chiefly Late Jurassic to early Tertiary age. The oldest rocks in the area are those of the Naknek Formation, consisting of volcaniclastic sandstone, siltstone, and conglomerate of Late Jurassic age. The southern part of the area includes rocks of the Belkofski Formation, a thick sequence of volcaniclastic sandstone, siltstone, and conglomerate of middle Tertiary age. Lava flows, volcanic breccia, and fluvial volcaniclastic rocks of late Miocene age, which unconformably overlie the Belkofski Formation south of the Emmons Lake volcanic center, are primarily exposed on the islands just south of the Alaska Peninsula. The Emmons Lake volcanic center was affected multiple times by glaciation associated with the glacier expansion that characterized the Quaternary. Glaciation has played a key role in shaping the present-day landscape, and much of the eruptive history of the Emmons Lake volcanic center has involved interactions with glacier ice. Thus, a brief review of the Quaternary glacial history of the area is provided to establish the physical context for Emmons Lake volcanic center eruptive activity.

Alaska↗
USGS2025

Utilizing crystal records to determine the underlying architecture and timescales of magmatic processes during the 2022 Mauna Loa eruption

Details of Mauna Loa’s plumbing system and magma storage dynamics are relatively poorly constrained, relative to nearby Kīlauea volcano. Recent studies have begun to address this gap in knowledge using geophysical imaging or olivine-focused petrology. Here, we use the crystal cargo from the 2022 summit and Northeast Rift Zone eruption to advance our understanding of Mauna Loa’s storage regions and pre˗eruptive processes. We identify textural and geochemical populations of olivine, orthopyroxene, clinopyroxene, and plagioclase macrocrysts as well as evolved glomerocrysts consisting of orthopyroxene, clinopyroxene, and plagioclase. Summit versus rift zone trends can be distinguished between specific crystal populations and are used to infer magma transfer pathways. Melt inclusion barometry from three orthopyroxene populations indicate crystallization depths of ~2–3 km which coincide with previous olivine˗hosted fluid inclusion barometry across Mauna Loa’s recent 200˗yr eruptive history. We combine orthopyroxene˗hosted melt inclusion barometry with diffusion chronometry on the same crystals using Fe˗Mg interdiffusion to estimate timescales of mixing and recharge prior to the eruption. Summit orthopyroxene yield timescales of weeks to months, aligning with geophysically recognized pre˗eruptive intrusion events and previously determined olivine timescales. Northeast Rift Zone orthopyroxene crystals have resorbed cores and yield short pre˗eruptive mixing timescales on the order of hours to days. Chemistry and timescales from the orthopyroxene populations suggest some of the 2022 magmas may have bypassed the shallowest portions of the summit reservoir system and were transferred directly into the rift zone syn˗eruptively.

Hawaii↗
USGS2025

Rhenium-osmium and oxygen isotope homogeneity during the 2022 Mauna Loa eruption and implications for basaltic magma storage

Mauna Loa is one of the largest and most active volcanoes on Earth. The most recent eruption of Mauna Loa started on 27 November 2022, lasted for 13 days, and was preceded by the longest repose time of 38 years in its modern history. In this contribution, new trace- and highly siderophile-element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances, 187 Re- 187 Os, and 18 O/ 16 O data are reported for the 2022 lavas. These lavas have a limited range of MgO (6.2 ± 0.1 wt.%) and Ni (83 ± 2 µg/g), with a broader range of Re (0.3 to 1.3 ng/g) and consistent Os (0.031 to 0.080 ng/g) contents. They have 187 Os/ 188 Os ratios (0.1345 to 0.1385) which are, on average, more radiogenic than Mauna Loa picrites (0.1331 to 0.1349) and are similar in composition to more differentiated Mauna Loa tholeiite lavas (0.1340 to 0.1381). The oxygen isotope compositions of glassy samples are 5.35 ± 0.15‰ ( n = 13) and span a range in δ 18 O of + 5.0 to + 5.5‰, with an average composition 0.2 to 0.3‰ lower than MORB. The δD value is − 81 ± 11‰ ( n = 5) at very low (0.03 ± 0.015 wt.%) H 2 O concentrations. The 2022 Mauna Loa eruption is similar in terms of δ 18 O but contrasts in terms of 187 Os/ 188 Os variability, with the recent longer-lived eruptions on La Palma (Canary Islands; 85 days) in 2021 and on the Reykjanes Peninsula (Iceland) that began in 2021 and are still ongoing. Initial lavas were more fractionated for both the Canary Islands and Iceland eruptions, producing more radiogenic Os isotope compositions than later erupted products. The 2022 Mauna Loa eruption showed no such trends. The limited range in isotope compositions of the 2022 Mauna Loa lavas and their strongly fractioned HSE patterns reflect long-term storage, crystal fractionation, and assimilation of related basaltic volcanic edifice materials by the parent magma beneath the volcano prior to eruption triggering. Eruption of differentiated and homogeneous tholeiite lavas at the summit caldera and high on the volcano’s flank, with emplacement of accumulative picrites lower on the volcano, are consistent with neutral buoyancy arguments.

Hawaii↗
USGS2024

Triggering the 2022 eruption of Mauna Loa

Distinguishing periods of intermittent unrest from the run-up to eruption is a major challenge at volcanoes around the globe. Comparing multidisciplinary monitoring data with mineral chemistry that records the physical and spatio-temporal evolution of magmas fundamentally advances our ability to forecast eruptions. The recent eruption of Mauna Loa, Earth’s largest active volcano, provides a unique opportunity to differentiate unrest from run-up and improve forecasting of future eruptions. After decades of intermittent seismic and geodetic activity over 38 years of repose, Mauna Loa began erupting on 27 November 2022. Here we present a multidisciplinary synthesis that tracks the spatio-temporal evolution of precursory activity by integrating mineral and melt chemistry, fluid inclusion barometry, numerical modeling of mineral zoning, syn-eruptive gas plume measurements, the distribution and frequency of earthquake hypocenters, seismic velocity changes, and ground deformation. These diverse data indicate that the eruption occurred following a 2-month period of sustained magma intrusion from depths of 3–5 km up to 1–2 km beneath the summit caldera, providing a new model of the plumbing system at this very high threat volcano. Careful correlation of both the geochemistry and instrumental monitoring data improves our ability to distinguish unrest from the run-up to eruption by providing deeper understanding of the both the monitoring data and the magmatic system—an approach that could be applied at other volcanic systems worldwide.

Hawaii↗
USGS2024

Geologic map of the northwest flank of Mauna Loa volcano, Island of Hawai‘i, Hawaii

Mauna Loa, the largest active volcano on Earth, has erupted 34 times since written descriptions became available in A.D. 1832. The most recent eruption of Mauna Loa occurred on November 27, 2022, after a 38 year hiatus; it lasted for 12 days. Some eruptions began with only brief seismic unrest, whereas others followed several months to a year of increased seismicity. Once underway, Mauna Loa’s eruptions can produce lava flows that may reach the sea in less than 24 hours, severing roads and utilities. For example, lava flows that erupted from the Southwest Rift Zone in 1950 advanced at an average rate of 9.3 kilometers per hour (5.8 miles per hour); all three lobes reached the ocean within ~24 hours. Near the eruptive vents, the flows likely traveled even faster. In terms of eruption frequency, pre-eruption warning, and rapid flow emplacement, Mauna Loa has great volcanic-hazard potential for the Island of Hawai‘i. Volcanic hazards on Mauna Loa can be anticipated, and risk substantially mitigated, by documenting its past activity to refine our knowledge of the hazards, and by alerting the public and local government officials of our findings and their implications for hazards assessments and risk. The map of the north and west flanks of Mauna Loa shows the distribution and relation of volcanic and surficial sedimentary deposits. It incorporates previously reported work published as generalized small-scale maps and a more detailed map. Within the mapped area, lava has flowed from three different source regions: the Northeast Rift Zone (22 percent), the summit (64 percent), and radial vents (14 percent). All three have different points of origin which, in turn, affect the flow characteristics and periodicity of activity. The map area includes the uppermost part of the NERZ and extends from the highest elevation––13,040 feet at the south end of the Kokoolau quadrangle, just below the summit caldera––to the sea northwest and west of the summit. Lava that erupts from the north and west flanks typically flows to the west, northwest, or north, depending on the vent location. Both morphologic lava flow types—‘a‘ā and pāhoehoe—are present. Pāhoehoe units tend to spread out or widen in low-slope regions, such as in the saddle regions between Mauna Loa and Mauna Kea or between Mauna Loa and Hualālai. In comparison, ʻaʻā flows generally produce narrower flow lobes that have higher relief. This map is the fifth in a series of five maps that will cover Mauna Loa volcano. NOTE: Map sheet 1 contains lines and type with overprint. This feature may be turned on or off in the Adobe Acrobat page display preferences.

Hawaii↗
USGS2023

Dynamics of magma mixing and magma mobilization beneath Mauna Loa – Insights from the 1950 AD Southwest Rift Zone eruption.

Eruptions from Mauna Loa’s Southwest Rift Zone (SWRZ) pose a significant threat to nearby communities due to high eruption rates and steep slopes resulting in little time for evacuation. Despite the large body of research done on Mauna Loa, knowledge of the timing and duration of magma residence and transfer through its internal plumbing system is still poorly constrained. This study presents a first quantitative look at thermochemical conditions and timescales of potentially deep storage and disaggregation of magmatic mush during the run-up to the voluminous 1950 AD SWRZ eruption. Details of heterogeneous compositions and textures of the macrocryst and glomerocryst cargo in 1950 AD lavas suggest magma mixing and crystal recycling along the entire plumbing system. Furthermore, the crystal cargo contains evidence for the direct interaction between primitive, deeply stored magma and pockets of more evolved magma stored at shallow to intermediate depths. An enigmatic attribute of 1950 near-vent lava is the near-ubiquitous presence of subhedral, unreacted Mg-rich orthopyroxene phenocrysts (Mg#>80). Phase relations of Mauna Loa olivine-tholeiite indicate that orthopyroxene joins olivine as a primary phase at pressures higher than 0.6 GPa. Coexisting Mg-rich olivine and orthopyroxene and the occurrence of harzburgitic (olivine-orthopyroxene) glomerocrysts provide evidence for cognate crystallisation at near-Moho (~ 18 km) depths (Thornber and Trusdell 2008 ). Petrogenetically diverse populations of glomerocrysts and macrocrysts alongside evidence of multilevel magma storage indicate a network of ephemeral and possibly interconnected magma pockets from near-Moho depths to the upper/mid-crust. Fe-Mg diffusion chronometry applied to 1950 AD olivine populations implies rapid mobilisation and transport of large volumes of magma (376×10 6 m 3 ) from near-Moho storage to the surface within less than 8 months, with little residence time (~ 2 weeks) in the shallow (3–5 km) plumbing system.

Hawaii↗
USGS2022

Explosive activity on Kilauea’s Lower East Rift Zone fueled by a volatile-rich, dacitic melt

Magmas with matrix glass compositions ranging from basalt to dacite erupted from a series of 24 fissures in the first two weeks of the 2018 Lower East Rift Zone (LERZ) eruption of Kīlauea Volcano. Eruption styles ranged from low spattering and fountaining to strombolian activity. Major element trajectories in matrix glasses and melt inclusions hosted by olivine, pyroxene and plagioclase are consistent with variable amounts of fractional crystallization, with incompatible elements (e.g., Cl, F, H 2 O) becoming enriched by 4-5 times as melt MgO contents evolve from 6 to 0.5 wt%. The high viscosity and high H 2 O contents (∼2 wt%) of the dacitic melts erupting at Fissure 17 account for the explosive Strombolian behavior exhibited by this fissure, in contrast to the low fountaining and spattering observed at fissures erupting basaltic to basaltic-andesite melts. Saturation pressures calculated from melt inclusions CO 2 -H 2 O contents indicate that the magma reservoir(s) supplying these fissures was located at ∼2-3 km depth, which is in agreement with the depth of a dacitic magma body intercepted during drilling in 2005 (∼2.5 km) and a seismically-imaged low Vp/Vs anomaly (∼2 km depth). Nb/Y ratios in erupted products are similar to lavas erupted between 1955-1960, indicating that melts were stored and underwent variable amounts of crystallization in the LERZ for >60 years before being remobilized by a dike intrusion in 2018. We demonstrate that extensive fractional crystallization generates viscous and volatile-rich magma with potential for hazardous explosive eruptions, which may be lurking undetected at many ocean island volcanoes.

Hawaii↗
USGS2020

Geologic map of the southern flank of Mauna Loa Volcano, Island of Hawai‘i, Hawaii

On the Island of Hawaiʻi, Mauna Loa, the largest volcano on Earth, has erupted 33 times since written descriptions became available in 1832. Some eruptions began with only brief seismic unrest, whereas others followed several months to a year of increased seismicity. Once underway, its eruptions can produce lava flows that may reach the sea in less than 24 hours, severing roads and utilities. In terms of eruption frequency, pre-eruption warning, and rapid flow emplacement, Mauna Loa has great volcanic-hazard potential for the Island of Hawai‘i. Volcanic hazards on Mauna Loa may be anticipated, and risk substantially mitigated, by documenting the past activity to refine our knowledge of the hazards and by alerting the public and local government officials of our findings and their implications for hazards assessments and risk. Although most Mauna Loa eruptions begin in the summit area at 12,000 feet (ft) elevation, the Southwest Rift Zone (SWRZ) was the source of at least 10 flank eruptions since 1843. The SWRZ extends from the summit towards Kalae (South Point) at sea level. The lowermost part of this rift zone, marked by Pu‘uʻoke‘oke‘o to the north at 6,874 ft elevation and extending to the sea, makes up the lower SWRZ. The community of Hawaiian Ocean View Estates, with a population of about 2,500, is the largest in the region. The subdivision is built entirely on flows erupted from southern Mauna Loa, and some source vents are located within the subdivision. Approximately 25 percent of the subdivision is within Hazard Zone 1. From east to west, the map covers the area from Punalu‘u to Miloli‘i and, from north to south, extends from north of Pu‘uʻoke‘oke‘o to Kalae (South Point). The map encompasses 1,163 square kilometers of the southwest flank of Mauna Loa, from 7,325 ft elevation to sea level. It shows the distribution of eruptive units (flows), which are separated into 16 age groups, ranging from more than 100,000 years before present to A.D. 1950. Lava erupted from the SWRZ typically flows to the west, east, or south (depending upon vent location relative to the rift crest) and generally produces narrow flow lobes. Both morphologic lava flow types—‘a‘ā and pāhoehoe—are present. In general, the northern part of the mapped area is dominated by flows from the middle SWRZ, whereas the southern part contains flows from the lower SWRZ and includes areas adjacent to, and downslope of, the rift zone. The exceptions are flows that originated from the upper SWRZ in the northeastern part of the Punaluu quadrangle.

Hawaii↗
USGS2020

Have humans influenced volcanic activity on the lower East Rift Zone of Kīlauea Volcano? A publication review

Since the 2018 eruption of Kīlauea Volcano, the topic of whether commercial developments not only caused the eruption to occur in the lower East Rift Zone (LERZ), but also caused its high eruption rate has been a subject of public discussion. We review Kīlauea Volcano publications from the past several decades and show that the eruptive behavior of the volcano has varied and that the 2018 eruption was similar to past eruptions in many ways. We find no evidence to support any human influence on Kīlauea Volcano.

Hawaii↗
USGS2019

Geologic map of the central-southeast flank of Mauna Loa Volcano, Island of Hawaii, Hawaii

Mauna Loa, the largest volcano on Earth, has erupted 33 times since written descriptions became available in 1832. Some eruptions began with only brief seismic unrest, while others followed several months to a year of increased seismicity. Once underway, its eruptions can produce lava flows that may reach the sea in less than 24 hours, severing roads and utilities. For example, lava flows erupted from the Southwest Rift Zone (SWRZ) in 1950 advanced at an average rate of 9.3 km per hour, and all three lobes reached the ocean within approximately 24 hours (Finch and Macdonald, 1953). Near the eruptive vents, the flows must have traveled even faster. In terms of eruption frequency, pre-eruption warning, and rapid flow emplacement, Mauna Loa poses an enormous volcanic-hazard threat to the Island of Hawai‘i. Volcanic hazards on Mauna Loa may be anticipated, and risk substantially mitigated, by documenting the past activity to refine our knowledge of the hazards and by alerting the public and local government officials of our findings and their implications for hazards assessments and risk. From the geologic record, we may deduce several generalized facts about the geologic history of the Northeast Rift Zone (NERZ). The middle to uppermost segments of the rift zone were more active in the past 4,000 years than the lower portion of the rift zone. This may be due to buttressing of the lower east rift zone by Mauna Kea and Kīlauea volcanoes. The historical flows that erupted on the north side of the rift zone advanced toward Hilo. This flank of the volcano may be more vulnerable to inundation. Lockwood (1990) noted that the vents of historical activity are migrating to the south. The volcano appears to have a self-regulating mechanism that evenly distributes long-term activity across its flanks. The geologic record also supports this notion; the time prior to the historical period (Age Group 1, pre-A.D. 1832 to 1,000 yrs B.P.; orange units) is dominated by activity on the south side of the NERZ. Although most Mauna Loa eruptions begin in the summit area at the 12,000-ft elevation (Lockwood and Lipman, 1987), the central-southeast flank has not been the source of any activity. All flows originated from the summit or the upper reaches of the Northeast Rift Zone (NERZ) or the Southwest Rift Zone (SWRZ). The NERZ was the source of eight flank eruptions since 1843. The NERZ extends from the 13,680-ft-high summit towards Hilo (population ~60,000; second-largest city in State of Hawaii). The northern portion of the map area is built entirely on flows erupted from the NERZ. The SWRZ extends from the summit towards Kalae (South Point) at sea level. The southern portion of the map area is built entirely on flows erupted from the SWRZ. The map area extends from the 10,350 -ft elevation on Mauna Loa’s east flank toward the Hawaii Volcanoes National Park and the town of Volcano (population approx. 2,000) in the northeast. At the south boundary of the map area is the town of Pāhala (population approx. 900). This map includes areas adjacent to and downslope of the NERZ and regions east of and directly downslope of Moku‘āweoweo, Mauna Loa’s summit caldera. The map encompasses 506 km 2 of the southeast flank (fig. 1) of Mauna Loa from 10,350 -ft elevation to sea level. The map of the central-southeast flank of Mauna Loa shows the distribution and relations of volcanic and surficial sedimentary deposits separated into 15 age groups ranging from a period greater than 50,000 yr B.P. to A.D. 1984. It incorporates previously reported work published in generalized small-scale maps (Lockwood and Lipman, 1987; Lockwood, 1995; Wolfe and Morris, 1996). This map is the second in a series of five maps that will cover Mauna Loa volcano. See SIM 2932-A at https://doi.org/10.3133/sim2932A . NOTE: Map sheet 1 contains lines and type with overprint. This feature may be turned on or off in the Adobe Acrobat page display preferences.

Hawaii↗
USGS2019

Digital database of the geologic map of the middle east rift geothermal subzone, Kīlauea Volcano, Hawai‘i

This database release contains all the information used to produce Geologic Investigations Series I-2614 ( https://pubs.usgs.gov/imap/2614/ ). The main component of this digital release is a geodatabase prepared using ArcGIS, but Esri shapefiles are included as well. Kīlauea is an active shield volcano in the southeastern part of the Island of Hawai‘i. The middle East Rift Zone (MERZ) map includes about 27 square kilometers of the MERZ and shows the distribution of the products of 34 separate eruptions during late Holocene time. Lava flows erupted during 1983–86 have reached the mapped area. The subaerial part of the MERZ is 3–4 km wide and about 18 km long. It is a constructional ridge, 50–150 m above the adjoining terrain, marked by low spatter ramparts and cones as high as 60 m. Lava typically flowed either northeast or southeast, depending on vent location relative to the topographic crest of the rift zone. The MERZ receives more than 100 inches of rainfall annually and is covered by tropical rain forest. Vegetation begins to grow on lava a few months after its eruption. Relative heights of trees can be a guide to relative ages of underlying lava flows, but proximity to faults, presence of easily weathered cinders, and human activity also affect the rate of growth. The rocks have been grouped into five basic age groups. The framework for the ages assigned is provided by eight radiocarbon ages from nearby mapping by the authors and a single date from within this investigation area. The numerical ages are supplemented by observations of stratigraphic relations, degree of weathering, soil development, and vegetative cover.

Hawaii↗
USGS2019

A high carbon content of the Hawaiian mantle from olivine-hosted melt inclusions

The deep mantle carbon content and flux are fundamental quantities in understanding global volatile cycles and distributions. Here, we present CO2 concentrations measured in 407 olivine-hosted melt inclusions from Hualalai, Kilauea, Koolau, Loihi, and Mauna Loa to constrain the Hawaiian mantle CO2 content and flux. Quantification of melt inclusion CO2 is complicated by the ubiquitous presence of vapor or “shrinkage” bubbles. The contribution from exsolved shrinkage bubble CO2 was determined from the measured bubble size and a CO2 equation of state, and added to the dissolved CO2 to reconstruct total melt inclusion CO2 concentrations. Bubbles typically contain ~90% of melt inclusion C, much of which may be sequestered in precipitated phases on bubble walls, and thus not amenable to measurement by Raman spectroscopy. Based on our dataset of total (dissolved + bubble) CO2 concentrations, we estimate that parental melts from the five Hawaiian volcanoes have CO2 concentrations ranging from 3900 to 10,000 ppm CO2. Among the active volcanoes, CO2 concentrations decrease to the northwest, likely reflecting mantle source heterogeneity, although differences in the depths of the magma chambers may also play a role. Mantle sources of the Hawaiian volcanoes range from 380 to 480 ppm CO2 suggesting that the Hawaiian plume is at least a factor of ~4 more C-rich than the MORB mantle. This enrichment is likely due to the presence of recycled surficial C and/or C-rich primitive material in the Hawaiian mantle.

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