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USGS2010

Eruptions of Hawaiian volcanoes—Past, present, and future

Viewing an erupting volcano is a memorable experience, one that has inspired fear, superstition, worship, curiosity, and fascination since before the dawn of civilization. In modern times, volcanic phenomena have attracted intense scientific interest because they provide the key to understanding processes that have created and shaped more than 80 percent of the Earth’s surface. The active Hawaiian volcanoes have received special attention worldwide because of their frequent spectacular eruptions, which often can be viewed and studied with relative ease and safety. In January 1987, the U.S. Geological Survey Hawaiian Volcano Observatory (HVO), then located on the caldera rim of Kīlauea, celebrated its 75th anniversary. To honor this anniversary, the U.S. Geological Survey (USGS) published Professional Paper 1350 , a comprehensive summary of the many studies on Hawaiian volcanism by USGS and other scientists through the mid-1980s. Drawing from the wealth of data contained in that volume, the USGS also published in 1987 the original edition of this general-interest booklet, focusing on selected aspects of the eruptive history, style, and products of two of the State of Hawaii’s active volcanoes—Kīlauea and Mauna Loa. A second edition of the booklet was published in 2010 to commemorate the Centennial of HVO (which occurred in January 2012), summarizing abundant new information gained since the January 1983 onset of Kīlauea’s middle East Rift Zone eruption at Pu‘u‘ō‘ō and the March 2008 beginning of Kīlauea’s summit lava-lake activity within Halema‘uma‘u. In this third edition, we include highlights from Kīlauea’s subsequent activity, including the 2018 eruption in the lower East Rift Zone—the largest and most destructive in at least 200 years—and associated summit-collapse events, the eruptions at Kīlauea’s summit since 2018, and the 2022 eruption of Mauna Loa, which occurred after 38 years of quiescence. It also considers new data leading to an improved history of Kīlauea’s explosive activity in the recent geologic past. This general-interest booklet is a companion to the one on Mount St. Helens volcano (southwestern Washington) first published in 1984, revised in 1990. Together, these publications illustrate the contrast between the two main types of volcanoes: shield volcanoes, such as those in the State of Hawaii, which generally are nonexplosive to weakly explosive; and composite volcanoes, such as Mount St. Helens in the Cascade Range, which generally erupt explosively.

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USGS2016

Feasibility study of earthquake early warning (EEW) in Hawaii

The effects of earthquake shaking on the population and infrastructure across the State of Hawaii could be catastrophic, and the high seismic hazard in the region emphasizes the likelihood of such an event. Earthquake early warning (EEW) has the potential to give several seconds of warning before strong shaking starts, and thus reduce loss of life and damage to property. The two approaches to EEW are (1) a network approach (such as ShakeAlert or ElarmS) where the regional seismic network is used to detect the earthquake and distribute the alarm and (2) a local approach where a critical facility has a single seismometer (or small array) and a warning system on the premises. The network approach, also referred to here as ShakeAlert or ElarmS, uses the closest stations within a regional seismic network to detect and characterize an earthquake. Most parameters used for a network approach require observations on multiple stations (typically 3 or 4), which slows down the alarm time slightly, but the alarms are generally more reliable than with single-station EEW approaches. The network approach also benefits from having stations closer to the source of any potentially damaging earthquake, so that alarms can be sent ahead to anyone who subscribes to receive the notification. Thus, a fully implemented ShakeAlert system can provide seconds of warning for both critical facilities and general populations ahead of damaging earthquake shaking. The cost to implement and maintain a fully operational ShakeAlert system is high compared to a local approach or single-station solution, but the benefits of a ShakeAlert system would be felt statewide—the warning times for strong shaking are potentially longer for most sources at most locations. The local approach, referred to herein as “single station,” uses measurements from a single seismometer to assess whether strong earthquake shaking can be expected. Because of the reliance on a single station, false alarms are more common than when using a regional network of seismometers. Given the current network, a single-station approach provides more warning for damaging earthquakes that occur close to the station, but it would have limited benefit compared to a fully implemented ShakeAlert system. For Honolulu, for example, the single-station approach provides an advantage over ShakeAlert only for earthquakes that occur in a narrow zone extending northeast and southwest of O‘ahu. Instrumentation and alarms associated with the single-station approach are typically maintained and assessed within the target facility, and thus no outside connectivity is required. A single-station approach, then, is unlikely to help broader populations beyond the individuals at the target facility, but they have the benefit of being commercially available for relatively little cost. The USGS Hawaiian Volcano Observatory (HVO) is the Advanced National Seismic System (ANSS) regional seismic network responsible for locating and characterizing earthquakes across the State of Hawaii. During 2014 and 2015, HVO tested a network-based EEW algorithm within the current seismic network in order to assess the suitability for building a full EEW system. Using the current seismic instrumentation and processing setup at HVO, it is possible for a network approach to release an alarm a little more than 3 seconds after the earthquake is recorded on the fourth seismometer. Presently, earthquakes having M≥3 detected with the ElarmS algorithm have an average location error of approximately 4.5 km and an average magnitude error of -0.3 compared to the reviewed catalog locations from the HVO. Additional stations and upgrades to existing seismic stations would serve to improve solution precision and warning times and additional staffing would be required to provide support for a robust, network-based EEW system. For a critical facility on the Island of Hawaiʻi, such as the telescopes atop Mauna Kea, one phased approach to mitigate losses could be to immediately install a single station system to establish some level of warning. Subsequently, supporting the implementation of a full network-based EEW system on the Island of Hawaiʻi would provide additional benefit in the form of improved warning times once the system is fully installed and operational, which may take several years. Distributed populations across the Hawaiian Islands, including those outside the major cities and far from the likely earthquake source areas, would likely only benefit from a network approach such as ShakeAlert to provide warnings of strong shaking.

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USGS2014

Magma supply, storage, and transport at shield-stage Hawaiian volcanoes

The characteristics of magma supply, storage, and transport are among the most critical parameters governing volcanic activity, yet they remain largely unconstrained because all three processes are hidden beneath the surface. Hawaiian volcanoes, particularly Kīlauea and Mauna Loa, offer excellent prospects for studying subsurface magmatic processes, owing to their accessibility and frequent eruptive and intrusive activity. In addition, the Hawaiian Volcano Observatory, founded in 1912, maintains long records of geological, geophysical, and geochemical data. As a result, Hawaiian volcanoes have served as both a model for basaltic volcanism in general and a starting point for many studies of volcanic processes. Magma supply to Hawaiian volcanoes has varied over millions of years but is presently at a high level. Supply to Kīlauea’s shallow magmatic system averages about 0.1 km 3 /yr and fluctuates on timescales of months to years due to changes in pressure within the summit reservoir system, as well as in the volume of melt supplied by the source hot spot. Magma plumbing systems beneath Kīlauea and Mauna Loa are complex and are best constrained at Kīlauea. Multiple regions of magma storage characterize Kīlauea’s summit, and two pairs of rift zones, one providing a shallow magma pathway and the other forming a structural boundary within the volcano, radiate from the summit to carry magma to intrusion/eruption sites located nearby or tens of kilometers from the caldera. Whether or not magma is present within the deep rift zone, which extends beneath the structural rift zones at ~3-km depth to the base of the volcano at ~9-km depth, remains an open question, but we suggest that most magma entering Kīlauea must pass through the summit reservoir system before entering the rift zones. Mauna Loa’s summit magma storage system includes at least two interconnected reservoirs, with one centered beneath the south margin of the caldera and the other elongated along the axis of the caldera. Transport of magma within shield-stage Hawaiian volcanoes occurs through dikes that can evolve into long-lived pipe-like pathways. The ratio of eruptive to noneruptive dikes is large in Hawai‘i, compared to other basaltic volcanoes (in Iceland, for example), because Hawaiian dikes tend to be intruded with high driving pressures. Passive dike intrusions also occur, motivated at Kīlauea by rift opening in response to seaward slip of the volcano’s south flank.

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USGS2014

One hundred volatile years of volcanic gas studies at the Hawaiian Volcano Observatory

The first volcanic gas studies in Hawai‘i, beginning in 1912, established that volatile emissions from Kīlauea Volcano contained mostly water vapor, in addition to carbon dioxide and sulfur dioxide. This straightforward discovery overturned a popular volatile theory of the day and, in the same action, helped affirm Thomas A. Jaggar, Jr.’s, vision of the Hawaiian Volcano Observatory (HVO) as a preeminent place to study volcanic processes. Decades later, the environmental movement produced a watershed of quantitative analytical tools that, after being tested at Kīlauea, became part of the regular monitoring effort at HVO. The resulting volatile emission and fumarole chemistry datasets are some of the most extensive on the planet. These data indicate that magma from the mantle enters the shallow magmatic system of Kīlauea sufficiently oversaturated in CO 2 to produce turbulent flow. Passive degassing at Kīlauea’s summit that occurred from 1983 through 2007 yielded CO 2 -depleted, but SO 2 - and H 2 O-rich, rift eruptive gases. Beginning with the 2008 summit eruption, magma reaching the East Rift Zone eruption site became depleted of much of its volatile content at the summit eruptive vent before transport to Pu‘u ‘Ō‘ō. The volatile emissions of Hawaiian volcanoes are halogen-poor, relative to those of other basaltic systems. Information gained regarding intrinsic gas solubilities at Kīlauea and Mauna Loa, as well as the pressure-controlled nature of gas release, have provided useful tools for tracking eruptive activity. Regular CO 2 -emission-rate measurements at Kīlauea’s summit, together with surface-deformation and other data, detected an increase in deep magma supply more than a year before a corresponding surge in effusive activity. Correspondingly, HVO routinely uses SO 2 emissions to study shallow eruptive processes and effusion rates. HVO gas studies and Kīlauea’s long-running East Rift Zone eruption also demonstrate that volatile emissions can be a substantial volcanic hazard in Hawai‘i. From its humble beginning, trying to determine the chemical composition of volcanic gases over a century ago, HVO has evolved to routinely use real-time gas chemistry to track eruptive processes, as well as hazards.

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USGS2024

Infrasound for volcano monitoring

Introduction Volcanic eruptions produce acoustic waves when volcanic gases and hot material rapidly expand in the atmosphere. Volcanic activity can produce acoustic signals with a wide range of frequencies, from very long period (>10 seconds) to audible (>20 hertz [Hz]), but the most energetic band is typically in the infrasound from 0.5 to 20 Hz. Studies of volcanic infrasound and the deployment of infrasound for volcano monitoring have increased rapidly in the past two decades as sensors have improved and as analytical tools have become more widely available. Improved sensors and tools have led to a growing diversity of eruptive activity being recorded and characterized, from Hawaiian to Plinian eruption styles at scales from local to global (Johnson and Ripepe, 2011; Fee and Matoza, 2013). Infrasound sensors on volcanoes are most commonly deployed locally with seismic stations, and the combination of co-located seismic and infrasound is more useful for characterizing unrest and detecting changes in activity than either data stream alone (for example, Lyons and others, 2016; Fee and others, 2017a; Matoza and others, 2018). At local (<15 kilometers [km]) to regional (15–250 km) distances from volcanoes, arrays of infrasound sensors are commonly deployed to detect coherent signals, constrain the direction to the source, and provide information on eruption dynamics; thus, infrasound is well suited to regional monitoring of volcanoes when local sensor networks are not feasible. A common usage of infrasound data in an observatory is to provide rapid confirmation that an explosion has occurred (for example, Coombs and others, 2018), although near-real-time eruption intensity quantification is also possible (Fee and others, 2010a; Ripepe and others, 2018; fig. C1). Infrasound is well suited to this task because it is not affected by clouds or precipitation and can propagate long distances with little attenuation. However, wind and ocean noise also produce infrasound, and spatiotemporal variability in the atmosphere can affect the propagation of infrasound, so care must be taken when deploying, analyzing, and interpreting the data. In addition to detecting and monitoring explosive activity, investigations of infrasound records from eruptions help constrain source processes, which in turn enhance syneruptive forecasting capabilities (for example, Fee and others, 2017b; Lyons and others, 2019). The following is a description of the capabilities recommended for real-time monitoring of eruptive phenomena with infrasound. Infrasound is also beginning to be used for tracking hazardous surface flows that occur on volcanoes, including pyroclastic density currents (Ripepe and others, 2010), lahars (Johnson and Palma, 2015), debris flows (Marchetti and others, 2019), snow avalanches (Havens and others, 2014), and lava flows (Patrick and others, 2019). Please refer to the chapter on lahars (this volume; Thelen and others, 2024a) for more information on this application.

Scientific Investigations Report↗

USGS2014

Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes

Study of the petrology of Hawaiian volcanoes, in particular the historically active volcanoes on the Island of Hawai‘i, has long been of worldwide scientific interest. When Dr. Thomas A. Jaggar, Jr., established the Hawaiian Volcano Observatory (HVO) in 1912, detailed observations on basaltic activity at Kīlauea and Mauna Loa volcanoes increased dramatically. The period from 1912 to 1958 saw a gradual increase in the collection and analysis of samples from the historical eruptions of Kīlauea and Mauna Loa and development of the concepts needed to evaluate them. In a classic 1955 paper, Howard Powers introduced the concepts of magnesia variation diagrams, to display basaltic compositions, and olivine-control lines, to distinguish between possibly comagmatic and clearly distinct basaltic lineages. In particular, he and others recognized that Kīlauea and Mauna Loa basalts must have different sources. Subsequent years saw a great increase in petrologic data, as the development of the electron microprobe made it possible to routinely monitor glass and mineral compositions, in addition to bulk rock compositions. We now have 100 years’ worth of glass compositions for Kīlauea summit eruptions, which, together with expanding databases on prehistoric tephras, provide important constraints on the nature of Kīlauea’s summit reservoir. A series of chemically distinctive eruptions in the 1950s and 1960s facilitated evaluation of magma mixing and transport processes at Kīlauea. At Mauna Loa, lava compositions are distinctive only at the trace element level, suggesting that its summit reservoir is better mixed than Kīlauea’s. Most summit lavas at both volcanoes, however, lie on olivine control lines having the same olivine composition (Fo 86–87 ). Study of the ongoing East Rift Zone eruption at Kīlauea has further illuminated the complexity of magma storage, resupply, and mixing along this very active rift zone. Studies of active and closed-system lava lakes have been part of HVO’s efforts since Jaggar’s unique descriptions of the Halema‘uma‘u lava lake that existed before 1924. Detailed study of closed-system bodies, including the 1959 Kīlauea Iki, 1963 ‘Alae, and 1965 and prehistoric Makaopuhi lava lakes and the Uēkahuna laccolith, have allowed recognition and quantification of processes of basalt differentiation. Specific topics reviewed herein include the occurrence of segregation veins and related structures, overall cooling history, and patterns of crystallization and reequilibration of olivine in various lava lakes. In recent decades, study of the submarine slopes of the Island of Hawai‘i and of Lō‘ihi Seamount has revolutionized our understanding of the early history of Hawaiian volcanoes. Observations of Lō‘ihi lavas first established the existence of an early alkalic stage in the evolution of Hawaiian volcanoes. Stages of volcanic development from inception to tholeiitic shield building can be observed in Kīlauea’s submarine and subaerial sections. One distinctive feature of submarine volcanics at Kīlauea, Mauna Loa, and Hualālai is that picritic lavas are more abundant than in subaerial eruptions. Also, olivine compositions of submarine lavas are more magnesian, ranging from Fo 88 at Kīlauea to Fo 89 at Hualālai. The most magnesian glasses known from Kīlauea (MgO=14.7–15.0 weight percent) were found along the submarine part of Kīlauea’s East Rift Zone. Contributions to our knowledge of the nature of the mantle source(s) of Hawaiian basalts are reviewed briefly, although this is a topic where debate is ongoing. Finally, our accumulated petrologic observations impose constraints on the nature of the summit reservoirs at Kīlauea and Mauna Loa, specifically whether the summit chamber has been continuous or segmented during past decades.

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USGS2014

Two hundred years of magma transport and storage at Kīlauea Volcano, Hawai'i, 1790-2008

This publication summarizes the evolution of the internal plumbing of Kīlauea Volcano on the Island of Hawaiʻi from the first documented eruption in 1790 to the explosive eruption of March 2008 in Halemaʻumaʻu Crater. For the period before the founding of the Hawaiian Volcano Observatory in 1912, we rely on written observations of eruptive activity, earthquake swarms, and periodic draining of magma from the lava lake present in Kīlauea Caldera. After 1912 the written observations are supplemented by continuous measurement of tilting of the ground at Kīlauea’s summit and by a continuous instrumental record of earthquakes, both measurements made during 1912–56 by a single pendulum seismometer housed on the northeast edge of Kīlauea’s summit. Interpretations become more robust following the installation of seismic and deformation networks in the 1960s. A major advance in the 1990s was the ability to continuously record and telemeter ground deformation to allow its precise correlation with seismic activity before and after eruptions, intrusions, and large earthquakes. We interpret specific events in Kīlauea’s 200- year written history as steps in a broad transition from summit lava-lake activity in Kīlauea Caldera to shield building on the east rift zone. The ability of the magmatic plumbing to deliver magma to eruption is critical to the history of eruption and intrusion. When the rate of magma supply equals the rate of eruption, there is little ground deformation or intrusion. When the magma supply rate is greater than the rate of eruption, then the edifice responds through any or all of summit inflation, intrusion, increased spreading rate, and large flank earthquakes. In Kīlauea’s 200-year history we identify three regions of the volcano in which magma is stored and supplied from below. Source 1 is at 1-km depth or less beneath Kīlauea’s summit and fed Kīlauea’s summit lava lakes throughout most of the 19th century and again from 1907 to 1924. Source 1 was used up in the series of small Halemaʻumaʻu eruptions following the end of lava-lake activity in the summit collapse of 1924. Source 2 is the magma reservoir at a depth of 2–6 km beneath Kīlauea’s summit that has been imaged by seismic and deformation measurements beginning in the 1960s. This source was first identified in the summit collapses of 1922 and 1924. Source 3 is a diffuse volume of magma-permeated rock between 5 and 11 km depth beneath the east rift zone and above the near-horizontal decollement at the base of the Kīlauea edifice. Magma distribution within source 2 has been derived by combining petrologic study of the three chemically uniform summit eruptions of 1952, 1961, and 1967–68 and the east rift eruptions within this interval with both observation of migrating centers of inflation determined from leveling surveys conducted before the 1967–68 eruption and with published models of expected deformation from different source geometries. We adopt a model of concatenated magmatic plugs with nodes beneath the inflation centers. Addition of erupted and intruded volumes of the three summit magma batches yields a liquid magma volume of about 0.2 km3, with dimensions of ~1 km by 1 km by 200 m centered at about 3-km depth within source 2. Following the Halemaʻumaʻu eruption of 1967–68, the chemistry of magma coming into Kīlauea’s summit reservoir has changed frequently, and during the eruption that began in 1983, chemical changes have been subtle and continuous. In this period we interpret changes in chemistry as related to an increase in magma supply resulting from increased partial melting in an expanding mantle source volume. We know from instrumental recording of eruptions since the long Halemaʻumaʻu eruption in 1952 that stress in the edifice accumulates as magma is added underground and is relieved by eruption and by dilation of the rift zones associated with seaward movement (spreading) of Kīlauea’s south flank. During and after the last half of the 20th century, magma transfer to the rift zone has dominantly occurred from source 2. High rates of flank motion have been correlated with high rates of endogenous growth; alternatively, lower rates of motion have characterized periods when the underground magmatic plumbing was being refilled following lateral removal of magma, as well as periods when a more open magmatic plumbing favored continuous eruption. Since at least 1952, source 3 has not drained during deflations, which was apparently not the case before 1924. Triangulation and leveling conducted in 1912, 1921, and 1926, combined with post-1912 tilt measurements, identified a broad regional uplift in 1918–19 and an equally broad collapse in 1924, neither of which has been seen since. We associate these elevation changes with addition or subtraction of magma from all three magma sources, dominantly source 3. We interpret the intrusion beneath the east rift zone during the 1924 collapse to have stabilized the rift zone-south flank relationship, preventing loss of magma from source 3 in subsequent collapses. Rates of seaward spreading were low until 1952, when earthquakes in 1950 and 1951 associated with surges of magma from the hotspot triggered a large offshore south flank earthquake swarm that unlocked the south flank and enabled a greatly increased rate of seaward spreading. Magma supply rates have been derived for the entire period of study. Between 1823 and 1840, magma was supplied from source 1 at a very high rate of more than 0.2 km 3 /yr, which we interpret as recovery from a substantial draining of magma from beneath Kīlauea in 1790. Inferred magma supply rates diminished to one-tenth of that value after 1840, in part because of increase in the activity of Mauna Loa beginning in 1843. Magma supply rates between 1918 and 1924 were about 0.024 km 3 /yr, matching that of the period from 1840 to 1894. During 1950–52 the magma supply rate increased to about 0.06 km 3 /yr, in part because of the great reduction in Mauna Loa activity following its large eruption in June 1950. Following the summit eruption of 1967–68, magma supply increased further to ~0.1 km 3 /yr, and further increases to more than 0.2 km 3 /yr occurred during the east rift eruption that began in 1983. Eruption at Kīlauea’s summit took place in 1952, and eruptive activity steadily increased as increased magma supply also drove increased spreading rates. The inability of magma supply to be accommodated by a combination of eruption and spreading during the 1969–74 Mauna Ulu period stressed Kīlauea’s south flank. The stress was relieved in part by the M7.2 earthquake of 29 November 1975. That earthquake, in turn, dilated Kīlauea’s east rift zone as the south flank moved seaward, producing a favorable condition for continuous east rift eruption, which began in 1983. The 1975 earthquake also resulted in the ability of the south flank to move independently under the influence of gravity, effectively decoupling the spreading rate from changes in the magma supply rate. The continuing increase in magma supply after 1983 was instead manifested in rift dilation, increased intrusion, and ultimately in the launching of a second eruption in Halemaʻumaʻu in March 2008, the first instance in Kīlauea’s recorded history of simultaneous eruption at the summit and on the east rift zone. Kīlauea’s history can be considered in cycles of equilibrium, crisis, and recovery. The approach of a crisis is driven by a magma supply rate that greatly exceeds the capacity of the plumbing to deliver magma to the surface. Crises can be anticipated by inflation measured at Kīlauea’s summit coupled with an increase in overall seismicity, particularly manifest by intrusion and eruption in the southwest sector of the volcano. Unfortunately the nature of the crisis—for example, large earthquake, new eruption, or edifice-changing intrusion—cannot be specified ahead of time. We conclude that Kīlauea’s cycles are controlled by nonlinear dynamics, which underscores the difficulty in predicting eruptions and earthquakes.

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