nasa-gesdisc/es-publications-researchareas huggingface dataset:
Multispectral discrimination of spectrally similar hydrothermal minerals in mafic crust: A 5000 km2 ASTER alteration map of the Oman–UAE ophiolite (2022)

Multispectral remote sensing of hydrothermal alteration in volcanogenic massive sulfide (VMS) ore systems in mafic crust is relatively uncommon, in part due to the short-wave infrared spectral similarity of several key alteration minerals: epidote, chlorite, actinolite, and serpentine. In this study, we developed regional mosaic generation and classification workflows for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery to discriminate these minerals over the entire crust of the Semail ophiolite (OmanUAE). Spectral discrimination was achieved through adaptation of the ASTER (pre-)processing workflow to the specific mapping targets, available datasets, and location of this study. Necessary steps included the pre-selection of ASTER scenes without residual atmospheric water features, mosaic normalization based solely on overlapping target outcrops, correcting cross-mosaic ramp errors, and alteration map classification based on image-derived reference data. The resulting alteration map, validated through comparison with field mapping and sampling, is the most areally extensive continuous survey of hydrothermal alteration yet presented for oceanic crust, providing a renewed framework for research and mineral exploration of Earth's largest ophiolite. Our map confirms that the vast majority of the upper oceanic crust is regionally altered to a spilite type secondary mineral assemblage. Localized areas of epidosite alteration, marking focused hydrothermal flow paths, are confined to the upper oceanic crust, whereas areas of previously unrecognized but intense actinolite alteration are common in both the lower and upper oceanic crust. Our methodological developments expand the standard considerations necessary for regional geological mapping using infrared image mosaics. They further demonstrate the underappreciated capability of multispectral data for mapping spectrally similar rock types. Although the specifics of the method are necessarily optimized for the OmanUAE ophiolite, re-optimization based on local reference data should allow similar results to be achieved in other well-exposed mafic-hosted VMS districts.

Research areas: Volcanic Eruptions
Volcanic effects on climate: recent advances and future avenues (2022)

Volcanic eruptions have long been studied for their wide range of climatic effects. Although global-scale climatic impacts following the formation of stratospheric sulfate aerosol are well understood, many aspects of the evolution of the early volcanic aerosol cloud and regional impacts are uncertain. In the last twenty years, several advances have been made, mainly due to improved satellite measurements and observations enabling the effects of small-magnitude eruptions to be quantified, new proxy reconstructions used to investigate the impact of past eruptions, and state-of-the-art aerosol-climate modelling that has led to new insights on how volcanic eruptions affect the climate. Looking to the future, knowledge gaps include the role of co-emissions in volcanic plumes, the impact of eruptions on tropical hydroclimate and Northern Hemisphere winter climate, and the role of eruptions in long-term climate change. Future model development, dedicated model intercomparison projects, interdisciplinary collaborations, and the application of advanced statistical techniques will facilitate more complex and detailed studies. Ensuring that the next large-magnitude explosive eruption is well observed will be critical in providing invaluable observations that will bridge remaining gaps in our understanding.

Research areas: Volcanic Eruptions
Monitoring endogenous growth of open-vent volcanoes by balancing thermal and SO2 emissions data derived from space (2019)

Measuring the amount of magma intruding in a volcano represents one of the main challenges of modern volcanology. While in closed-vent volcanoes this parameter is generally assessed by the inversion of deformation data, in open-vent volcanoes its measurement is more complicated and results from the balance between the magma entering and leaving the storage system. In this work we used thermal and SO2 flux data, derived from satellite measurements, to calculate the magma input and output rates of Mt. Etna between 2004 and 2010. We found that during the analysed period more magma was supplied than erupted, resulting into an endogenous growth rate equal to 22.9  13.7  106 m3 y1. Notably, this unbalance was not constant in time, but showed phases of major magma accumulation and drainage acting within a compressible magma chamber. The excellent correlation with the inflation/deflation cycles measured by ground-based GPS network suggests the thermal, SO2 flux and deformation data, can be combined to provide a quantitative analysis of magma transport inside the shallow plumbing system of Mt Etna. Given the global coverage of satellite data and the continuous improvement of sensors in orbit, we anticipate that this approach will have sufficient detail to monitor, in real time, the endogenous growth associated to other world-wide open-vent volcanoes.

Research areas: Volcanic Eruptions
ICESat-2 Applications for Investigating Emerging Volcanoes (2022)

Submarine volcanism in shallow waters (<100 m), particularly in remote settings, is difficult to monitor quantitatively and, in the rare formation of islands, it is challenging to understand the rapid-paced erosion. However, these newly erupted volcanic islands become observable to airborne and/or satellite remote sensing instruments. NASAs ICESat-2 satellite laser altimeter, combined with visible imagery (optical and microwave), provide a novel method of evaluating the elevation characteristics of newly emerged volcanoes and their subaerial eruption products. Niijima Fukutoku-Okanoba (NFO) is a submarine volcano 1300 km south of Tokyo (Ogasawara Archipelago of Japan) that periodically breaches the ocean surface to create new islands that are subsequently eroded. The recent eruption in August 2021 is a rare opportunity to investigate this island evolution using high-resolution satellite datasets with geodetic-quality ICESat-2 altimetry. Lansdat-8 and Planet imagery provide a qualitative analysis of the exposed volcanic deposits, while ICESat-2 products provide elevation profiles necessary to quantify the physical surface structures. This investigation determines an innovative application for ICESat-2 data in evaluating newly emerged islands and how the combination of satellite remote sensing (visible and lidar) to investigate these short-lived volcanic features can improve our understanding of the volcanic island system in ways not previously possible.

Research areas: Volcanic Eruptions
Air quality impacts of the 2018 Mt. Kilauea volcano eruption in Hawaii: A regional chemical transport model study with satellite-constrained emissions (2020)

Volcanic eruptions emit a vast amount of sulfur dioxide (SO2) and ash into the air, often imposing substantial impacts on air quality and the ecosystem. Quantifying its impacts, however, is difficult due to the uncertainties in estimating the strength and variations of volcanic emissions. Here we developed and evaluated a new approach to combine satellite SO2 detection and chemical transport modeling to assess the impact of the 2018 Mt. Kilauea eruption on air quality over Hawaii. During the sustained eruption of the Kilauea Volcano in Hawaii's Big Island from May to July 2018, considerable SO2 and PM2.5 enhancements were observed both from the ground and from space. We studied this case using an experimental version of the NOAA National Air Quality Forecast Capability (NAQFC) modeling system. Daily emissions of SO2 and ash were estimated using a combination of SO2 column density retrieved by Ozone Mapping and Profiling Suite (OMPS) Nadir-Mapper (NM) aboard the Suomi-NPP satellite and the NAQFC model with an inverse emission modeling approach. We found that the volcanic SO2 emission rates peaked at 15,000 mol/s from the Kilauea's East Rift zone and Summit. The formation and transport of volcanic smog, or Vog, was highly dependent upon the vertical distribution of the volcanic emission, controlled by the heat flux of emission sources. We conducted four model simulations with various emission settings, and compared them to satellite data (CALIOP, OMPS and VIIRS) and in-situ measurements. All the runs tended to underpredict the peak values of surface SO2 and PM2.5 (particulate matter smaller than 2.5 m in diameter). The No Plume Rise run underestimated the Vog plume rise and downstream transport. Using fixed emission rate or removing the temporal variations (3-Day Mean) led to miss peak Vog effects or inconsistent transport pattern compared to the observations. Therefore, the Base simulation with daily-varying emission and plume rise was used to quantify the air quality effects of the Kilauea eruption. We found that the volcanic eruption elevated surface PM2.5 concentration by 3040 g/m3 in the southeast part of the Big Island, with peak values up to 300 g/m3. The Vog effect on trace gases, such as O3, NOx, and non-methane hydrocarbons, were much weaker (<1 ppbV), but extended to farther downstream.

Research areas: Volcanic Eruptions, Air Quality
Volatile Content Implications of Increasing Explosivity of the Strombolian Eruptive Style along the Fracture Opening on the NE Villarrica Flank: Minor Eruptive Centers … (2021)

Potential flank eruptions at the presently active Villarrica, Southern Andes Volcanic Zone (33.346 S) require the drawing of a comprehensive scenario of eruptive style dynamics, which partially depends on the degassing process. The case we consider in this study is from the Los Nevados Subgroup 2 (LNG2) and constitutes post-glacial minor eruptive centers (MECs) of basalticandesitic and basaltic composition, associated with the northeastern Villarrica flank. Petrological studies of the melt inclusions volatile content in olivine determined the pre-eruptive conditions of the shallow magma feeding system (<249 Mpa saturation pressure, 9271201 C). The volatile saturation model on pressure-dependent volatile species, measured by Fourier Transform Infrared Microspectrometry (FTIR) (H2O of 0.43.0 wt.% and CO2 of 1141586 ppm) and electron microprobe (EMP), revealed that fast cooling pyroclasts like vesicular scoria preserve a ~1.5 times larger amount of CO2, S, Cl, and volatile species contained in melt inclusions from primitive olivine (Fo7686). Evidence from geological mapping and drone surveys demonstrated the eruption chronology and spatial changes in eruption style from all the local vents along a N45 corridor. The mechanism by which LNG2 is degassed plays a critical role in increasing the explosivity uphill on the Villarrica flank from volcanic vents in the NE sector (<9 km minimum saturation depth) to the SW sector (<8.1 km), where many crystalline ballistic bombs were expulsed, rather than vesicular and spatter scoria.

Research areas: Volcanic Eruptions
Reservoir depressurization driven by passive gas emissions at Ambrym volcano (2022)

Despite being a widespread and common process, the impact of passive volcanic degassing on the pressurization state of a magma reservoir is not well understood. If mass loss due to gas emissions results in reservoir depressurization and surface subsidence, the pressure difference between a shallow reservoir and deep magma source may result in magma recharge and eventually trigger an eruption. It is therefore important to determine how a simplified reservoir-conduit system responds to such degassing processes. Here we use an extreme example of persistent volcanic degassingAmbrymas a case study to relate sulphur dioxide mass flux with reservoir depressurization and edifice-scale subsidence, both measured from satellite-based remote sensing observations. A geodetic inversion of surface displacements measured with Interferometric Synthetic Aperture Radar modeled using the Boundary Element Method provides bounds on the reservoir pressure change during an episode of subsidence at Ambrym from 2015 to 2017. These results are input into a lumped parameter theoretical model developed by Girona et al. (2014), and the free parameters (e.g., reservoir size and conduit radius) are systematically explored. We find that the 20152017 subsidence episode is consistent with pressure decreasing at a rate of 5.2 to 2.0 MPa year1 in a reservoir at 2 km b.s.l., as a result of passive degassing. The subsidence episode is observed to end abruptly in October 2017, and no significant deformation is detected in the 14 months leading up to a rift zone intrusion and submarine eruption in December 2018, despite substantial degassing. We explain this lack of pre-eruptive deformation by an influx of 0.16 km3 of magma into a shallow (<2 km b.s.l.) reservoir that counterbalances the depressurization caused by degassing. This recharge volume is comparable with the volume of magma subsequently extracted from Ambrym's reservoir in December 2018. We conclude that at some open-vent passively degassing volcanoes, deflation caused by degassing may reduce or even cancel any inflation signal caused by magma influx. Nonetheless, detection of pre-eruptive recharge can be achieved by monitoring changes in the long-term deformation rate.

Research areas: Volcanic Eruptions
Stratospheric temperature and ozone anomalies associated with the 2020 Australian New Year Fires (2021)

Stratospheric aerosol, temperature, and ozone anomalies after the 2020 Australian bushfires are documented from satellite observations. Aerosol extinction is enhanced in the Southern Hemisphere (SH) lower stratosphere (LS) in early 2020, comparable in magnitude to the Calbuco eruption in 2015. Warm temperature anomalies of 1-2 K occur in the SH LS during January-April 2020 and are coincident with enhanced aerosols. Radiative heating is indicated through anomalous temperature correlations between lower and higher latitudes. LS ozone shows midlatitude decreases several months after the aerosol maximum and before the polar vortex breakup, reaching extreme minima over the available OMPS record since 2011. Antarctic ozone depletion in the LS in 2020 reached a decadal low for both magnitude and persistence during November-December, along with record low polar temperatures and a strong polar vortex. Overall, the polar ozone depletion, temperature, and polar vortex evolution broadly resembled the effects of the Calbuco eruption in 2015.

Research areas: Wildfires, Volcanic Eruptions
Multidisciplinary Constraints on Magma Compressibility, the Pre‐Eruptive Exsolved Volatile Fraction, and the H2O/CO2 Molar Ratio for the 2006 Augustine Eruption … (2021)

Geodetically modeled reservoir volume changes during volcanic eruptions are commonly much smaller than the observed eruptive volumes. This discrepancy is thought to be partially due to the compressibility of magma, which is largely controlled by the presence of exsolved volatiles. The 2006 eruption of Augustine Volcano, Alaska, produced an eruptive volume that was ∼3 times larger than the geodetically estimated syn-eruptive subsurface volume change. In this study, we use a multistep methodology that combines constraints from geodetic, volcanic gas, geologic, and petrologic data together with equations relating physical processes to observable parameters. We apply a Monte Carlo approach to quantify uncertainties. Ultimately, we solve for the exsolved volatile volume fraction and the magma compressibility. We estimate Augustine's 2006 pre-eruptive exsolved volatile phase to be ∼5.5 vol% of the magma at storage depths, yielding a bulk magma compressibility of ∼3.8 × 10<SUP>-10</SUP> Pa<SUP>-1</SUP>. We develop a novel approach to estimate the H<SUB>2</SUB>O/CO<SUB>2</SUB> ratio of the syn-eruptive gas emissions in the absence of direct H<SUB>2</SUB>O emission measurements which are hard to obtain due to the high background levels in ambient air. We find a best-fit H<SUB>2</SUB>O/CO<SUB>2</SUB> molar ratio of 29. We also investigate the effects of applying different equations of state to our model. We find that the Ideal Gas Law might be used as a first approximation due to its simplicity; however, it overestimates volatile density and compressibility significantly at storage depths. This project capitalizes on the insights that can be gained by integrating multidisciplinary data with models of physical processes.

Research areas: Volcanic Eruptions
Detection of geothermal anomalies using Landsat 8 TIRS data in Tulu Moye geothermal prospect, Main Ethiopian Rift (2018)

Despite the high geothermal potential of the Main Ethiopian Rift (MER), risks associated with the industry and the difficulty of identifying possible targets using ground surveys alone continue to impede the development of geothermal power diligence in Ethiopia. In this paper, we investigate the geothermal potential of the Tulu Moye prospect area in the MER using Landsat 8, which is an important and cost-effective method of detecting geothermal anomalies. Data with a path/row of 168/054 were obtained from the Landsat 8 Operational Land Imager (OLI) and Thermal Infrared (TIR) sensors for October 17, 2014. Based on radiometric calibration, atmospheric correction (with the 6S model) and an NDVI-based threshold method for calculating land surface emissivity, a split-window algorithm was applied to retrieve the land surface temperature (LST) of the study area. Results show LST values ranging from 292.2 to 315.8 K, with the highest values found in barren lands. A comparison of LST between the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat 8 shows a maximum difference of 1.47 K. Anomalous areas were also discovered, where LST was about 3-9 K higher than the background area. We identified seven of these as areas of high geothermal activity in the Tulu Moye prospective geothermal area. Auxiliary data and overlay analysis tools eliminated any non-geothermal influences. The research reveals that the distribution of highy prospective geothermal areas is consistent with the development and distribution of faults in the study area. Magmatism is the thermal source and faults provide conduits for the heat to flow from earths interior to the surface, facilitating the presence of geothermal anomalies. Finally, TIR remote sensing methods prove to be a robust and cost-effective technique for detecting LST anomalies in the geologically active area of MER. Moreover, combining TIR remote sensing with knowledge of the structural geology of the area and geothermal mechanisms is an efficient approach to detecting geothermal areas.

Research areas: Volcanic Eruptions
Diverse Eruptive Activity Revealed by Acoustic and Electromagnetic Observations of the 14 July 2013 Intense Vulcanian Eruption of Tungurahua Volcano, Ecuador (2018)

During the powerful July 2013 eruption of Tungurahua volcano, Ecuador, we recorded exceptionally high amplitude, long-period infrasound (1,600-Pa peak-to-peak amplitude, 5.5-s period) on sensors within 2 km of the vent alongside electromagnetic signals from volcanic lightning serendipitously captured as interference. This explosion was one of Tungurahua's most powerful vulcanian eruptions since recent activity began in 1999, and its acoustic wave is among the most powerful volcanic infrasound ever recorded anywhere. We use these data to quantify erupted volume from the main explosion and to classify postexplosive degassing into distinct emission styles. Additionally, we demonstrate a highly effective method of recording lightning-related electromagnetic signals alongside infrasound. Detailed chronologies of powerful vulcanian eruptions are rare; this study demonstrates that diverse eruptive processes can occur in such eruptions and that near-vent infrasound and electromagnetic data can elucidate them.

Research areas: Volcanic Eruptions
Integrated hazards maps of the Tacaná Volcanic complex, Mexico-Guatemala: Ashfall, block-and-ash flows, and lahars (2021)

The Tacana Volcanic Complex (TVC) is an active volcano, located on the border between Mexico and Guatemala, in the westernmost part of the Central American Volcanic Arc. The TVC has produced effusive and explosive activity during the past 300 ka through the emplacement of lava flows, pyroclastic deposits, debris avalanches and lahars. During the last 10 ka, at least 11 eruptions have occurred, with three small phreatic explosions documented in 18551856, 1949 and 1986. This work presents volcanic hazards maps of the TVC that integrate the results of analyzing two eruptive style scenarios: dome-collapses and Plinian-type eruptions and the lahars triggered by both these hazards. The extents and expected distributions for each of these phenomena were assessed using numerical models and the results were calibrated with recent field data. The simulation results were merged to prepare three new volcanic hazards maps, which depict on a color scale the hazard level forecasted for each phenomenon (high  red, moderate  orange, and low  yellow). The maps show that the total extension of block-and-ash flows will be restricted towards the volcano base, reaching a maximum distance towards Guatemala of ~5 km, and ~10 km in Mexico; while lahars could reach up to 50 km downstream along the main rivers that drains the complex (i.e. Coatan, Cahoacan and Suchiate rivers) that would flood important urban centers mostly over Mexican territory. Ashfall would cover an area of ca. 8000 km2, inhabited by ~2 million people in both countries. Hence, renewed eruptive activity of the TVC would be catastrophic not only because of the loss of human life but also for its adverse impact on economic activity based on corn, coffee, and banana plantations, together with the disruption of communication and transportation systems between Mexico and Central America.

Research areas: Volcanic Eruptions
Springtime Stratospheric Volcanic Aerosol Impact on Midlatitude Cirrus (2022)

Explosive volcanic eruptions can reach the stratosphere and cause elevated concentrations of sulphate particles for months to years. When these particles descend into the troposphere, they can impact cirrus clouds though to what degree is unknown. In this study, we combine three satellite data sets to investigate the impact of downwelling sulphate aerosol on midlatitude cirrus clouds during springtime. The results show that cirrus clouds in the northern hemisphere (NH) have lower ice water content (IWC), ice crystal number concentrations, and cloud fraction (CF) when the aerosol load in the lowermost stratosphere is elevated by volcanism. These changes are largest for the coldest clouds at the highest altitudes. The cirrus clouds in the southern hemisphere on the other hand show no significant changes with downwelling aerosol levels. The reduction in cirrus IWC and CF in the NH implies that volcanic aerosol can cool the climate through reduced warming from cirrus clouds.

Research areas: Volcanic Eruptions