New open access articles on Mauna Loa 2022 eruption
Recent publications in a special Bulletin of Volcanology volume, titled, "Mauna Loa 2022 – Unrest, Eruption, and Outreach at the World’s Largest Volcano," present multidisciplinary studies of Mauna Loa investigating magma storage and ascent, summit and rift zone dynamics, and fissure and lava flow processes and hazard assessments. Several of these papers are open access and available online.
The largest active volcano in the world, Mauna Loa (Island of Hawai‘i), erupted in November–December 2022, following 38 years of relative quiescence with punctuated periods of unrest. Heightened unrest began in mid-September 2022 with increased frequency of earthquakes beneath the summit, as well as increases in inflation rates recorded by GPS stations and on the summit tiltmeter. At this time, the U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) increased long-standing community outreach and interagency communications efforts (Mulliken et al. this volume).
The eruption began at 11:21 p.m. Hawaii Standard Time (HST) on 27 November 2022 through a series of fissures in the summit caldera Mokuʻāweoweo. Activity quickly migrated into the south caldera region and upper Southwest Rift Zone (Fig. 1). At 11:45 p.m. HST, HVO issued a Volcano Activity Notice (VAN) and Volcano Observatory for Aviation Notice (VONA) that Mauna Loa was erupting. By the early morning of 28 November 2022, activity at the summit ceased, and four fissures opened at high elevations (3365–3755 m) within the upper Northeast Rift Zone (Fig. 2). Lava effusion localized at fissure 3A by 2 December 2022, establishing a channel network that flowed down the north flank of Mauna Loa, feeding flows that ultimately reached within 2.7 km of Daniel K. Inouye State Highway 200 (commonly referred to as the “Saddle Road”) before stalling. The eruption produced multiple lava flows (the longest extending ~ 19 km), covering an area of 43 km2 with approximately 150 × 106 m3. On 13 December 2022, HVO put out a VAN/VONA stating that Mauna Loa had stopped erupting on 10 December 2022.
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.
Real-time lava flow forecasting during the 2022 Mauna Loa eruption response
On November 27, 2022, Mauna Loa (Hawai‘i) erupted for the first time in 38 years, initially producing lava flows that covered the floor of its summit caldera, Moku‘āweoweo. Over the first 12 h following the summit eruption, four main fissures opened on Mauna Loa’s Northeast Rift Zone, with “fissure 3” quickly becoming the dominant source of lava flows. For the next 12 days, fissure 3 produced a 19-km-long lava flow to the north, crossing the Mauna Loa Weather Observatory access road and coming within 2.8 km of inundating the Daniel K. Inouye Highway (Saddle Road). Within 40 min of fissure 3 opening, inundation modeling efforts had begun. For the duration of the eruption, the computational fluid dynamics model Lava2d was run in real time, using flow front locations and other field observations to make sequential forecast improvements, eventually producing a set of models which accurately predicted the routing and arrival times of lava from fissure 3. These models were used to inform timing estimates of possible future inundation of the Saddle Road. As the eruption progressed, almost 4000 Lava2d models were made using high-performance computing resources, providing critical information on uncertainty in multi-week forecasts. To our knowledge, this was the first ever real-time physics-based ensemble lava flow modeling and forecasting effort. Here, we present a chronology of these real-time efforts, focusing on the successes and limitations of this approach.
Mauna Loa’s short-lived eruption from late November to early December 2022 marked the culmination of nearly a decade of elevated seismic activity and geodetic inflation. The volcano has been monitored by a network of permanent, short period and broadband seismometers. I used the continuous waveform data from that network starting in 2012 to generate a catalog of seismicity that enhances the US Geological Survey Hawaiian Volcano Observatory’s public seismic catalog with four times the number of earthquakes, which were then grouped by waveform similarity. Analysis of subtle delays in the timing of arrivals of scattered waves between pairs of earthquakes in this catalog yields a history of small changes in the shallow seismic velocity structure of the volcano. Seismic velocities have been shown at other volcanoes to change during unrest and eruption. My results show a decrease in seismic velocity centered on the summit beginning in September 2022, corresponding to the onset of a vigorous precursory swarm of seismic activity and shallow inflation. During the eruption itself, I observe large changes due likely to dike opening along the northeast rift zone and deflation of the summit reservoir. However, seismic velocity changes associated with non-volcanic sources such as ground shaking from large earthquakes and meteorological influences at seasonal and diurnal time scales are also observed, and these dominate the velocity changes prior to the eruption. Proper accounting of these effects will be a requirement for use in real-time monitoring, and this work serves as a starting point in that endeavor for Mauna Loa.
There are few petrological constraints on magma storage depths at Mauna Loa, Hawai‘i. Yet understanding the geometry of the magmatic plumbing system is critical for interpreting geophysical signals of unrest at this very high-threat volcano. We address this gap by examining CO₂-rich fluid inclusions (FI) in lava and tephra from seven eruptions (8870 ± 56 14C yr BP, 1852, 1855, 1868, 1949, 1950, and 1984), supplemented with published data from 2022. Raman spectroscopy was used to determine FI densities, from which entrapment pressures were calculated using a CO₂-H₂O equation of state. Most FI record pressures of ~ 0.25–1.25 kbar (~ 2–5 km depth below the summit), consistent with geophysical estimates from the past 40 years. In summit eruptions, FI hosted in more evolved olivine and orthopyroxene clots (Fo and Mg# < 84) record slightly shallower pressures than those in more primitive olivines (Fo > 84) from rift zone eruptions, suggesting a crystal-poor evolved cap near the top of the reservoir (~ 2 km). The similarity in storage depths across all eight eruptions indicates that Mauna Loa’s magmas have tapped a quasi-stable reservoir over the past two centuries, and possibly over 10 kyr. Electron backscatter diffraction reveals deformations to the crystal lattice in Fo82-83 olivines, likely due to deformation during storage in mush piles. The intensity of deformation is comparable to that seen at Kīlauea, implying that mush pile stress may be decoupled from edifice size or longevity. Finally, SO₂ contents in FI increase from ~ 2 mol% at 2 kbar to ~ 15 mol% at 0.5 kbar, suggesting sulphur degassing begins far deeper than the 0.2–0.3 kbar commonly assumed for Hawaiian systems. This validates the newest generation of S degassing models (e.g., Sulfur_X), and explains precursory SO2 emissions in the ~3 hours prior to the onset of the 2022 eruption (Esse et al. 2025).
Mauna Loa volcano erupts crystal-poor material at its summit and more crystal-rich material on its rift zones. Some of the more olivine-rich lava flows contain xenoliths with diverse mineralogy, including cumulate harzburgites with high-Mg# orthopyroxenes and high-Fo olivines (both > 84). Previous experimental work and thermodynamic modelling has proposed that high-Mg# orthopyroxenes only crystallize from Mauna Loa melts at high pressures (> 6 kbar, > 20 km), leading to suggestions that there is a region of sub-Moho magma storage at Mauna Loa in addition to the geophysically imaged magma reservoir at 2–5 km depth below the summit. We use melt and fluid inclusion barometry combined with thermodynamic models to further investigate this suggestion. Fluid inclusion data from harzburgites and dunitic xenoliths yield storage depths remarkably similar to those found in non-xenolithic crystals from lavas and tephras, with a clear peak at ~ 2–3 km (below the summit). Depths from melt inclusions in these xenoliths overlap with fluid inclusion pressures, ruling out the possibility of fluid inclusion re-equilibration during a period of stalling in a shallower reservoir. We examine five different thermodynamic models and find that the minimum pressure of olivine-orthopyroxene co-saturation varies by ~ 4 kbar (~ 12 km). These models also fail to predict that orthopyroxene is stable in ~ 15–80% of compositionally relevant experimental charges which grew orthopyroxene. Overall, this shows that phase stability modelling is an unreliable method of determining magma storage depth at Mauna Loa. We suggest that model discrepancies reflect a lack of experimental constraints on orthopyroxene stability at > 1200 ℃ and 0.01–5 kbar. Based on the presence of large oikocrystic orthopyroxenes completely enclosing rounded olivine chadacrysts, we suggest that these harzburgitic xenoliths formed through the reaction of intruding melts with olivine mush piles within the Mauna Loa edifice at ~ 3 km depth below the summit, with no need for a deeper storage reservoir. The predominance of pre-eruptive shallow storage means that there is more chance of detecting reservoir destabilization with geophysical monitoring techniques compared to a scenario where melts are supplied from sub-Moho reservoirs.
Volcanic fissure eruptions can produce voluminous gas emissions, posing a risk to local and distal populations and potentially impacting global climate. Quantifying the emission rate and altitude of injection of these emissions allows forecasting of impacts and provides key insights into the magma dynamics driving eruptions. Daily global observations from satellite instruments such as TROPOMI combined with trajectory modelling with PlumeTraj deliver these emission rate and altitude data. Here, we report satellite-derived SO2 emissions from the 2022 eruption of Mauna Loa, which lasted only 13 days but produced an SO2 plume that circled the globe, displaying a highly variable emission rate and injection altitude. Three key discoveries were made: we detect precursory SO2 emissions up to 3 h before the eruption start; peaks in emission rate are correlated with onset and cessation of activity at different fissures; the SO2 injection altitude was modulated by the available moisture content of the ambient air. We suggest that alignment of the fissure geometry with the wind direction could potentially explain how the initial emissions reached 14 km asl, approaching the tropopause. The total SO2 measured from this eruption is 600 (± 300) kt. These results demonstrate how satellite measurements can provide new insights into eruptive and degassing mechanisms and highlight that better constraints on the SO2 emissions from fissure eruptions globally are needed to understand their impact on climate.
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, 187Re-187Os, and 18O/16O 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 187Os/188Os 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 δ18O 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.%) H2O concentrations. The 2022 Mauna Loa eruption is similar in terms of δ18O but contrasts in terms of 187Os/188Os 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.