Lava Research Articles

Methana Magmatic Observational Experiment (MeMaX) – seismological monitoring of magmatic and tectonic activity in the western Saronic Gulf region, Greece

Large-scale historical volcanic eruptions caused significant destruction in the Mediterranean region (e.g., Thera/Santorini explosion circa 1600 BCE). The South Aegean Volcanic Arc remains active, and in addition to primary volcanic hazards such as ashfall and lava flows, active submarine and coastal volcanoes have the potential to trigger tsunamis as secondary volcanic hazard. These tsunamis pose a threat even to far-distant coastlines. With increasing population density, infrastructure development, and seasonal tourism, both primary and secondary volcanic risks along the Aegean coasts are increasing, even with respect to smaller, more frequent eruptions. Our focus is on the western Saronic Gulf region within the Aegean Sea, as possible impacts may even extend into the greater Athens metropolitan area. There, the dormant volcanoes of the Methana volcanic system, which last erupted in 230 BCE, and the submarine Pausanias Volcanic Field pose an underappreciated hazard. We search for evidence of yet undetected magmatic activity through the identification of related microseismic events and describe the design of the related MeMaX experiment. Since 2019, the National Observatory of Athens and the University of Patras operate six seismic stations on Methana and the nearby Peloponnese mainland. In March 2024, an additional 15 seismic recording stations were deployed for a two-years period across Methana, Aegina, Agistri, Kyra, and Poros islands and the mainland Peloponnese. This network configuration provides a dense and good azimuthal coverage of seismic ray paths for earthquake location and structural analysis. The continuous recordings enhance the observational capacities for earthquake detection, e.g. the first results indicate that the noise at the recording sites is quite low and that low magnitude events to ML ca. 0 can be recorded with a very good signal-to-noise ratio. This geophysical experiment is partof the MULTI-MAREX initiative.

Paleomagnetic data from volcanic rocks in the southern Central Andes of Argentina and their implications for tectonics and geomagnetic field behavior

Abstract A paleomagnetic study of basaltic lava flows exposed in the northern Neuquén Cordillera, southernmost Central Andes, along the Antiñir-Copahue fault zone (ACFZ), involved 25 sites of the Cola de Zorro Formation (Pliocene–Early Pleistocene) along two different sections. The sites show exclusive normal polarity, corresponding to the Late Pliocene Gauss chron (3.6–2.6 Ma). The angular standard deviation of virtual geomagnetic poles (VGPs; ASD = 14.8°) is consistent with the expected values from recent geomagnetic models, in opposition to anomalously low dispersion found in previous studies in Pleistocene VGPs of reverse polarity from neighboring areas to our study zone. Mean paleomagnetic directions for Bella Vista (Dec = 0.0°, Inc = −50.0°, α₉₅ = 7.6°, K = 36.7, N = 11) and Río Huaraco sections (Dec = 354.9°, Inc = −57.0°, α₉₅ = 7.5°, K = 55.7, N = 8) do not show tectonic rotation around vertical axes. Combining and regrouping our and previous data by area confirmed the absence of tectonic rotations in the Huaraco-Trohunco block and a statistically significant clockwise rotation of 14.4° ± 10.3° of three adjacent tectonic blocks located south of our study locality in Pleistocene times. These results suggest that strike-slip deformation along some sections of the ACFZ was significant in the Pleistocene structural evolution of this region.

Studi Lokasi Evakuasi Masyarakat dalam Mitigasi Banjir Lahar Dingin di Sisi Selatan Gunung Marapi

This study aims to: 1) Map the cold lava flow zone on the south side of Mount Marapi. 2) Mapping the cold lava flood hazard zone on the south flank of Mount Marapi. 3) Mapping the location of community evacuation in mitigating cold lava flood on the south side of Mount Marapi. This type of research uses descriptive quantitative approach. Data collection techniques were literacy study, internet searching and field survey. Data processing analysis techniques using scoring and weighting methods. The data visualized in this research are 8 rivers upstream from the south side of Mount Marapi. The results of this research are: There are 3 results of this research: 1) Nagari located in the cold lava flood flow zone on the south side of Mount Marapi are Nagari in Tanah Datar Regency: Sungai Jambu, Parambahan, Limo Kaum, Simabur, Pariangan, Batu Basa, Padang Magek, Paninjauan, Panyalaian, Batipuh Ateh and Sumpur. Nagari in Padang Panjang City: Kota Panjang, Ngalau, Pasar Usang and Ganting. 2) There are 3 classes of cold lava flood hazard zones: low hazard 23.12%, medium hazard 46.44% and high hazard 30.44%. 3) 8 evacuation locations are obtained, namely in Nagari Batu Basa, Nagari Limo Kaum, Nagari Batipuah Ateh, Nagari Padang Panjang and Nagari Simabur.

Surface Deformation Dynamics of Sierra Negra's 2018 Eruption: Insights from InSAR, Optical Flow, and Pixel Offset Tracking

Summary Monitoring volcanic deformation is crucial for understanding volcanic behavior, but challenges like limited GNSS coverage, infrequent SAR data acquisitions, and coherence loss during eruptions complicate this task. Our study on the 2018 eruption of Sierra Negra utilizes Sentinel-1A/B images to track surface deformation patterns that revert to their initial state across three phases: before, during, and after the eruption. We implemented an adaptive workflow using the shortest temporal baseline of consecutive SAR image pairs, including InSAR, optical flow, and pixel offset tracking methods, to accurately capture surface displacement linked to the dynamics of the magma reservoir in the caldera and a nearby (sub-) horizontal dike. Results show that while the caldera subsided gradually over two months during lava flow (initially at a rate of several meters) until it began to uplift again, the northern region alternated between uplift and subsidence twice in the line-of-sight (LOS) direction. This pattern suggests repeated magma injections into the sub-horizontal dike sustained the lava flows from the northeastern fissure. The one-day difference between SAR images from ascending and descending tracks enabled us to estimate the underground magma transfer rate at approximately 60 m/h, which aligns with the magma migration trajectory indicated by seismic data. By integrating InSAR and offset tracking methods, we provide a comprehensive view of surface displacement throughout the volcanic eruption cycle.

Petrogenesis and Geochemistry of Upper Paleozoic Komatiites (Mashhad, NE Iran)

Abstract Upper Paleozoic, probably Permian, komatiites have been found in the Paleo Tethys suture zone in NE Iran. These rocks are divided into three groups: (i) differentiated and undifferentiated komatiite lava flows, (ii) komatiitic basalts, and (iii) ultramafic-mafic pillow lavas. The rocks have a wide range of textures including random olivine spinifex, layered olivine spinifex, random and string-beef pyroxene spinifex, micrographic intergrowths of plagioclase and clinopyroxene, and cumulate textures. MgO contents range from 7.1 wt% in basalts and gabbros in differentiated flows to 38.0 wt% in cumulates, flow margins and samples with olivine spinifex textures. The MgO content of the parental melt is estimated using the Fo content of olivine (89-91) to be between 20 and 25 wt%, and the higher MgO content in spinifex samples (30 to 36 wt%) is attributed to accumulation of olivine. The rocks have low Al2O3/TiO2 and are relatively depleted in heavy rare earth elements. They therefore are classified as Al-depleted komatiite, the first report of this magma type in a Phanerozoic locality. These characteristics are attributed to the presence of garnet in the source during mantle melting and melt extraction. The rocks also have relatively low contents of the more incompatible trace elements indicating derivation from a depleted source. Our study indicates that the parental magma formed by 10- (about) 20% partial melting in a mantle plume at pressures of about 4-5 GPa (depths of 120-150 km). Ascent of the plume into the Late Paleozoic subduction zone at the margin of the Paleo-Tethys ocean is a possible petrogenetic model for the generation of these komatiites.

The viscous-brittle transition in flowing crystal-bearing volcanic dome lavas

The ascent and advance of volcanic dome lava is non-linear and viscoelastic. There exists a mismatch between current theoretical approaches to dome lava rheology, which are based on rheological laws for viscous suspensions, and empirical experimental approaches to convolved viscous-brittle deformation, which show mixed evidence for simultaneous lava flow and fracturing. The missing requirement is a unified framework for understanding the transition between micro-mechanical flow mechanisms that are dominantly viscous, and those that include micro-cracking in multiphase suspensions such as magmas. Here, we use high-temperature compression rheology with sample-scale acoustic emission analysis to constrain the conditions under which crystal-rich volcanic dome lava can flow by mixed viscous and brittle fracturing processes at small scales, leading to ‘crackling’ acoustic signals, even at moderate shear stresses extant in nature. Using multi-directional permeability measurements on large 60 mm diameter quenched samples of natural magmas, we show that this micro-cracking flow mechanism leads to permeability anisotropy, localizing outgassing into pathways that are off-axis relative to the direction of flow. Finally, we use a scaling approach and a database of published observations from real eruptions to upscale our findings, and show that bulk, apparently ductile flow of low-porosity dome magma is likely to involve a local mixed-mode of micro-cracking and viscous flow during the shallowest portions of ascent and during emplacement on the Earth's surface. The micro-cracking involved in lava advance divorces real crystal-bearing lava emplacement from most current rheology models based on a purely viscous micro-mechanism and shows that a revised solution for the rheology of mixed brittle-viscous flow is required. By re-examining published numerical models for dome emplacement, we demonstrate that the viscous-brittle transition can be intercepted in spatially heterogeneous zones within the dome core.

A Model Framework for Scaling Pre‐Quaternary Cosmogenic Nuclide Production Rates

AbstractCosmogenic nuclide dating is an essential component of studying Earth surface processes, but it requires knowledge of how nuclide production rates vary in time and space. Typically, production rates are calibrated at sites with independently well‐constrained exposure histories and then scaled to other sites of interest using scaling frameworks that account for spatial and temporal variations in the secondary cosmic‐ray flux at Earth's surface. To date, scaling schemes for terrestrial cosmogenic nuclide production rates have been developed for the Quaternary, yet cosmogenic nuclide applications that extend beyond the Quaternary are becoming more prevalent. For these deeper time applications, production rate calculations using scaling models optimized for the latest Quaternary neglect longer term spatiotemporal variations in geomagnetic field intensity, paleogeography, and paleoatmospheric depth. We present a production rate scaling scheme for the past 70 million years, SPRITE (Scaling Production Rates In deep TimE). This framework extends existing scaling schemes into deeper time by (a) accounting for site‐specific changes in paleolatitude, (b) integrating a geomagnetic field intensity model rooted in data from a global paleomagnetic database, and (c) incorporating climate‐driven, time‐varying atmospheric depths. We evaluate the efficacy of our model by applying it to existing data sets from paleoexposure sites, and from sites with apparent continuous million‐year exposure histories. This scaling model can be applied with measurements of stable cosmogenic nuclides to research questions such as constraining hiatus durations between ancient lava flows and calculating the formation timescales of stable landforms in arid environments over millions of years.

Редкоземельная минерализация Печальнинского вулканического комплекса (Северо-Восток России)

The article presents the first data on rare-earth element-concentrating minerals in the Campanian Pechalny volcanic complex (Magadan Oblast). The volcanic complex is composed of a series of small subvolcanic rhyolite and trachyrhyolite intrusions, their explosive breccias, and basalts lava flow, which, judging by geochemical data, belong to typical intraplate bimodal magmatism. Rhyolites are extremely enriched in rare-earth elements of the lanthanide group (average REE total = 1152 ppm, max. up to 5662 ppm), as well as in Rb, Zr, Y, and Nb. The main rare-elementconcentrating minerals are monazite, allanite (orthite), gel-zircon, as well as Nb-bearing rutile and hematite. All minerals, except allanite, are characterized by a small grain size, from 15 μm to 2 μm and less. Unusual spheroid gel-zircon have been discovered; their genesis is associated with the hydrothermal stage of volcanism, at high oxidation state in a highly concentrated supercritical fluid.

Bioweathering in monogenetic volcanoes: the case of Xitle in Mexico City

This contribution describes biological weathering features produced by microbial communities growing on rock surfaces denominated biological rock crusts. We provide arguments related to the importance of recognizing rocks as an ecological niche and a review of main recognized bio-weathering processes in basaltic bedrock. We particularly address the features found in the lava flow of the monogenetic volcano Xitle, which is located in the volcanic field of the Sierra del Chichinautzin in the south of Mexico City. We found that the diversity and distribution of organisms within the rock crusts varies depending on the superficial texture and porosity of the lavas. Mosses have a preference for vesicles and crevices, while lichens can establish in smoother and more exposed areas. The predominant biological weathering features we have found associated with these crusts are incrustation, penetration, vesicle infilling, endolithic colonization, fractures, and particle entrapment. It is worth noting that bioweathering features are related to specific biological groups: lichens exert all of the features found, while mosses are mostly associated with particle entrapment and vesicle infilling, and biofilms are related to penetration and endolithic colonization. Therefore, this article discusses the importance of geoheritage conservation in relation to the biodiversity these lavas harbor.

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.

Increased metamorphic conditions in the lower crust during oceanic transform fault evolution

Abstract. Oceanic transform faults connect the segments of active spreading ridges that slide past each other. In a classical view, transform faults are considered conservative, where no material is added or destroyed. Recent studies, however, suggest that the crust in the transform fault region is deformed during different episodes and is therefore non-conservative. We combine high-resolution 3D broadband seismic data with shipborne potential field data to study ancient oceanic fracture zones in Albian–Aptian aged oceanic crust in the eastern Gulf of Guinea offshore São Tomé and Príncipe. The crust in this region is characterized by a thin, high-reflective upper crust, underlain by a thick, almost seismically transparent lower crust. At the paleo-transform faults, the lower crust, however, comprises reflectors, which dip towards the transform fault and were previously interpreted as extrusive lava flows at an extensionally thinned inside corner. The lower crust therefore defines the target area for inversion and forward modeling of the potential field data. The chosen seismic horizons are used as geometrical boundaries of the crustal model. First, we perform a lateral parameter inversion for the lower crust, which provides vertical columns of density and magnetic susceptibility. Second, we sort the estimated values using a clustering approach and identify five groups with common parameter relationships. Third, we use the clustered lower-crustal domains to define a consistent 3D model of the study area that aligns with the seismic structure and geological concepts, which is preferred over the simple inversion of the first step. The final model generally shows anomalous low susceptibility and medium to high densities close to the buried fracture zones, which reflects increasing pressure and temperature as the transform faults evolved. This is accompanied by a change in metamorphic facies from prehnite-pumpellyite to greenschist. Our model indicates evolving extension and a second magmatic phase during juxtaposition against the trailing ridge segment. These results are in line with recent studies and strengthen the impressions of a widespread non-conservative character of transform faults.

The Development of Disaster Risk Map for Semeru Volcano Eruption 2021-2022, East Java, Indonesia

The Semeru Volcano eruption on December 4, 2021 caused damage to social, economic and environmental aspects. The Rejali Watershed (DAS) is one of the areas severely affected due to the eruption. The eruption resulted in 51 deaths, 10,565 displaced people, 1,027 houses damaged, two connecting routes and 43 public facilities damaged. This study mapped the disaster risk areas due to the eruption of Semeru Volcano. This research used Laharz to analyze the lava flow hazard map and weighting for social, economic, physical, environmental, and capacity vulnerability parameters. The results showed that the risk level of Semeru Volcano eruption is divided into three classes: high, medium, and low risk. The high-risk area is 8915.09 Ha (14 %), the medium-risk area is 2174.74 Ha (17 %), and the low-risk area is 1885.60 Ha (69%). The high and medium risks were located on the upper and middle slopes of the Rejali watershed because the upstream area experiences a narrowing of the river flow (bottleneck) due to direct borders with structural land. The Semeru Volcano disaster risk map results can be used as a reference in sustainable risk management efforts in the Rejali watershed to reduce the impact and damage caused by the eruption.

Reappraising the eruptive history of the Alchichica Maar Volcano (Mexico) based on Sr–Nd isotopes: Understanding the role of the magma source region on the growth of small-volume volcanoes

Alchichica Maar is in the eastern sector of the Trans-Mexican Volcanic Belt, where volcanics range from basalts to rhyolites, with 87Sr/86Sr and 143Nd/144Nd values between 0.70293 to 0.70447 (εSr = −21.1 to −4.5) and 0.512733 to 0.512949 (εNd = +3.4 to +6.2), respectively. In this study, Nd and Sr isotopic data and new major and trace elements compositions are provided for the lava flow, the scoria cone, and the phreatomagmatic deposits composing Alchichica Maar Volcano. These results are used in combination with published data to reexamine its eruptive history, though to be formed by more than one eruptive event. The cogeneticy of the magmas that fed the eruptions of these deposits is examined to infer the role of the deep magma source region and post-magmatic alterations on the construction of the Alchichica Maar magmatic system. Alchichica samples present 87Sr/86Sr values between 0.70387 and 0.70447 (εSr = −9.0 to −0.4) and 143Nd/144Nd values from 0.512749 to 0.512773 (εNd = +2.0 to +2.8). While the 87Sr/86Sr values suggest a slight increment in radiogenic 87Sr from the pre-maar lower lava flow to the upper maar eruptions indicative of magma contamination within the upper crust and by hydrodynamic mingling during the phreatomagmatic phases, the slight variation in Nd isotopes suggest an overall homogeneous source where small batches of magmas formed episodically to feed monogenetic eruptions, which subsequently yielded the pre-maar lava flow, the pre-maar surge, the scoria cone, and the maar units. This study reinforces the idea that an already “tapped” source region of a monogenetic volcano may become fertile again, and new eruptions can occur from near or old vent sites. It also highlights the hazardous potential of small-volume volcanoes.

Comparison of Airborne Magnetic and Ground Magnetic for Identification of Sub-surface Condition Study Case Sand Caldera of Bromo-Tengger Volcanic Complex : Preliminary Study

Abstract The Bromo-Tengger Volcano Complex is a popular geotourism destination characterized by volcanic activity also unique geological and geomorphology settings. However, limited geophysical investigations have been conducted in this area, particularly using magnetic methods, to understand the subsurface conditions. Thus, this study aims to compare geophysical methods which are airborne and ground magnetic survey methods to identify the sub-surface conditions of Bromo-Tengger Volcano Complex. Airborne magnetic measurements were conducted using a Geotron Proton Precision Magnetometer G5 as the base and a Sensys Magdrone R3 with a DJI M600 drone as the rover with 5 ms of spacing, providing rapid coverage of large areas and minimizing interference. Ground magnetic measurements were taken using only a Geotron Proton Precision Magnetometer G5 for base and rover with 200 meters of spacing. Ground magnetic measurements serve as a comparison to assess resolution and potential data loss caused by factors such as flight altitude and data sampling rate. Combining both magnetic survey measurements enables a comprehensive understanding of the magnetic properties of the surveyed area. The airborne magnetic survey produced 2,097,134 data points in just two days, while the ground magnetic survey produced only 174 points in ten days. Although the airborne magnetic survey is less detailed, it can effectively interpret the subsurface conditions. On the other hand, the ground magnetic survey provides high-resolution results but is affected by local noise and temporal changes. Both surveys identified high anomalies in the southern and northeastern regions, which were interpreted as basalt lava flows. Medium anomalies are believed to be early pyroclastic fall deposits, while low anomalies indicate subsurface volcanic activity. Overall, the results of the airborne magnetic survey correlate well with the ground magnetic survey, making it a viable and time-saving alternative to large-scale magnetic measurements.

Seventeen Million Years of Episodic Volcanism Recorded Within the Geologist Seamounts: Implications for Tectonic Drivers of Intraplate Volcanism

AbstractUpwelling and decompression of mantle plumes is the primary mechanism for large volumes of intraplate volcanism; however, many seamounts do not correlate spatially, temporally, or geochemically with plumes. One region of enigmatic volcanism in the ocean basins that is not clearly attributable to plume‐derived magmatism is the Geologist Seamounts and the wider South Hawaiian Seamount Province (∼19°N, 157°W). Here we present new bathymetric maps as well as 40Ar/39Ar age determinations and major and trace element geochemistry for six remote‐operated vehicle recovered igneous rock samples (NOAA‐OER EX1504L3) and two dredged samples (KK840824‐02) from the Geologist Seamounts. The new ages indicate that volcanism was active from 90 to 87 Ma and 74 to 73 Ma, inferring that in conjunction with previous ages of ∼84 Ma, seamount emplacement initiated near the paleo Pacific‐Farallon spreading ridge and volcanism spanned at least ∼17 m.y. Geochemical analyses indicate that Geologist Seamount lava flows are highly alkalic and represent low‐degree partial mantle melts primarily formed from a mixture of melting within the garnet and spinel stability field. The ages and morphology inferred that the seamounts were likely not related to an extinct plume. Instead, we build upon previous models that local microblock formation corresponded to regional lithospheric extension. We propose that the microblock was bounded by the Molokai and short‐lived Kana Keoki fracture zones. Regional deformation and corresponding volcanism among the Geologist Seamounts associated with the microblock potentially occurred in pulses contemporaneous to independently constrained changes in Pacific Plate motion—indicating that major changes in plate vectors can generate intraplate volcanism.

Novel age constraints on offshore islets around Taiwan with implications for the Northern Taiwan Volcanic Zone

Determining the exact age of volcanic activity in the Northern Taiwan Volcanic Zone (NTVZ) is essential for comprehending Taiwan's tectonic evolution. The timing and duration of the volcanic processes that formed the NTVZ remain uncertain despite the availability of geochronological, geochemical, and geophysical data. While extensive efforts have been directed towards investigating the age of the Tatun Volcanic Group, the primary feature of the NTVZ, many other aspects require further examination. This study concentrates on two offshore islets in the northern region of the NTVZ. We present new 40Ar/39Ar ages of 0.252 ± 0.018 Ma for a lava flow, representing an early stage of volcanic activity, and 0.118 ± 0.012 Ma for a dike, representing the latest stage of volcanic activity around Pengjia Islet. A sample collected from Mianhua Islet did not yield a reasonable age due to high uncertainty, likely attributable to young and low radiogenic argon. Field observations support the interpretation that volcanic activity on both islets is considerably younger than previously estimated. This study corroborates the hypothesis from geophysical studies that submarine NTVZ features to record a potentially active magmatic reservoir offshore of northern Taiwan. By refining our understanding of spatio-temporal patterns in volcanic activity, this study contributes to volcanic hazard assessment in Taiwan and surrounding areas.

Volcanically induced glacier collapses in southern Jan Mayen (Sør‐Jan), Norway

Jan Mayen is a small volcanic island situated in the Norwegian–Greenland Sea. The entire island was covered by a contiguous ice cap during the Last Glacial Maximum. The deglaciation of the ice cap was interrupted by a glacier advance in the southern part of the island in the Early Holocene. Today, there are no glaciers in this area, and until now it has been unknown whether any glaciers survived there into the Middle–Late Holocene. We show here that glaciers existed at several sites in the mountain areas of southern Jan Mayen. The investigations were triggered by the discovery of a relict glacier completely covered by tephra and impacted by a lava flow. Samples of ice from the glacier have 18O values that are isotopically indistinguishable from modern precipitation values and fall along the local meteoric water line trend. The lava flow in the glacier catchment and sculpted forms along the base of dry meltwater channels in bedrock show that glacier melting was abrupt and marked by sudden meltwater outbursts (jökulhlaups). Three more sites in southern Jan Mayen have meltwater channels with sculpted beds, gorges and/or sediments associated with lava flows and can be attributed to jökulhlaups caused by rapidly melting glaciers. Radiocarbon dates associated with glacial outwash sediments, cosmogenic dates of meltwater channel incisions, and cosmogenic and K‐Ar dates of lava flows associated with former periods of rapid glacier melting show that the four glaciers collapsed at different times in the Holocene. None of the glaciers reformed after their collapses despite subsequent cooling event(s). Likely, the glaciers were on the brink of existence before their sudden demise.

Quantifying Volumes of Volcanic Deposits Using Time-Averaged ASTER Digital Elevation Models

Quantifying the volume of erupted volcanic material, particularly lava flows and domes, provides critical insights into the dynamics of an eruption. This in turn aids in future hazard modeling, mitigation, and response. However, acquiring the necessary topographic datasets to calculate volumetric change is difficult, especially for active volcanoes in remote regions. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument has acquired global photogrammetric data since 2000, from which individual scene digital elevation models (DEMs) are created. We present a new straight forward method using ASTER DEMs to measure the volume of emplaced lava flows, domes, and tephra cones. We focus on five case studies that represent different eruption styles and products. For each of these we compare the results to those from previous studies that used alternative topographic datasets, such as synthetic aperture radar (SAR), airborne photogrammetry, or Light Detection and Ranging (LiDAR) measurements. These datasets, however, are expensive to acquire or lack the needed temporal resolution. We show that in nearly all cases, our volume results are either within the reported range for the eruption or ≤ 0.05 km3 of the previously reported value derived from SAR or LiDAR. The simplicity of the ASTER DEM approach combined with the global coverage of the data products enables more timely production of accurate volumetric data during and following an eruption, which can then be used to assess past and future eruption dynamics.

Hot spot volcano emissions as a source of natural iron fertilization in the ocean

Dust deposition, river runoff and glacial melt are the main sources of trace metals to the surface ocean. In the Canary Islands, deposition is dominated by dry dust deposition from the Saharan desert. However, during 85 days, from 19 September to 13 December 2021, the main source of trace metals on the island of La Palma changed drastically. The eruption of the Tajogaite volcano released tonnes of volcanic ash. Concurrently, several lava flows reached the coastal waters. Volcanic activity on land became the main source of iron (Fe) into the coastal waters. Fe concentrations in seawater reached over 1900 nmol L−1. ∼99 % of the iron was found in the particulate phase (particles >0.2 μm wide; 1920 ± 50 nmol L−1). Colloids, smaller size particles (0.02 μm < colloids < 0.2 μm) represented ∼0.7 % of the iron pool (14.5 ± 0.5 nmol L−1). While the truly soluble phase represented ∼0.03 %. However, the soluble phase presented concentrations reaching 0.66 ± 0.05 nmol L−1, which is ∼10 times higher than generally found in open Atlantic Ocean waters. The results show how the Fe size fractionation evolved during the eruption, from a dominance of large particle phases to smaller-sized compounds.

KARAKTERISTIK BASAL DAERAH TANJUNG AGUNG

Research on crystalline rocks in Lampung has been carried out by various researchers, but this research still does not cover other areas, such as Tanjung Agung village, Katibung District, South Lampung. Therefore, this research aims to analyze the characteristics of basalt rocks in the Tanjung Agung area, South Lampung, which is important for expanding understanding of the geological diversity in the region. These rocks are found in the form of entablature-type columns formed from basalt lava flows. The methods used include literature studies, field observations, and laboratory analysis, especially petrographic analysis, to identify mineral content and rock structure to understand the crystallization process and formation of columnar joints. The results of the petrographic analysis show a porphyritic texture with plagioclase, pyroxene, and hornblende phenocrysts, as well as a finer groundmass. These rocks show gradual crystallization and textural variations such as trachytic, sieve, glomeroporphyritic, and zoning, which reflect processes of decompression, pressure reduction, and magma mixing. Based on the mineral composition, this rock is classified as basalt which undergoes a gradual crystallization process, namely the formation of large crystals (phenocrysts) at depth and the formation of a finer groundmass at the surface. This research also opens up opportunities for geochemical analysis to understand the origin and evolution of magma in the region. Thus, this research provides further insight into the dynamics of magmatism and rock formation in the Tanjung Agung area.