Santa Maria Volcano Research Articles

UAS-based tracking of the Santiaguito Lava Dome, Guatemala

Imaging growing lava domes has remained a great challenge in volcanology due to their inaccessibility and the severe hazard of collapse or explosion. Changes in surface movement, temperature, or lava viscosity are considered crucial data for hazard assessments at active lava domes and thus valuable study targets. Here, we present results from a series of repeated survey flights with both optical and thermal cameras at the Caliente lava dome, part of the Santiaguito complex at Santa Maria volcano, Guatemala, using an Unoccupied Aircraft System (UAS) to create topography data and orthophotos of the lava dome. This enabled us to track pixel-offsets and delineate the 2D displacement field, strain components, extrusion rate, and apparent lava viscosity. We find that the lava dome displays motions on two separate timescales, (i) slow radial expansion and growth of the dome and (ii) a narrow and fast-moving lava extrusion. Both processes also produced distinctive fracture sets detectable with surface motion, and high strain zones associated with thermal anomalies. Our results highlight that motion patterns at lava domes control the structural and thermal architecture, and different timescales should be considered to better characterize surface motions during dome growth to improve the assessment of volcanic hazards.

Localised magmatic constraints on continental back-arc volcanism in southern Mendoza, Argentina: the Santa Maria Volcano

The Payun Matru Volcanic Field constitutes part of the continental back-arc in Argentina. This volcanic field has been the focus of several regional investigations; however, geochemical analysis of recent volcanoes (<8 ka) at the scale of an individual volcano has not been conducted. We present a morphological description for the Santa Maria Volcano in addition to results from major and trace element analysis and 238U-230Th-226Ra disequilibria. The trace element evidence suggests that the Santa Maria magmatic source has a composition similar to that of the local intraplate end member (resembling an ocean island basalt-like source), with a slight contribution from subduction-related material. The U-series analyses suggest a high 226Ra excess over 230Th for this volcano, which is not derived from a shallow process such as hydrothermal alteration or upper crustal contamination. Furthermore, intermediate-depth processes such as fractional crystallisation have been inferred for the Santa Maria Volcano, but they are not capable of producing the 226Ra excess measured. The 226Ra excess is explained by deep processes like partial melting of mantle lithologies with some influence from subducted Chilean trench sediments. Due to the short half-life of 226Ra (1600 years), we infer that fast magma ascent rates are required to preserve the high 226Ra excess.

Volcanic plume vent conditions retrieved from infrared images: A forward and inverse modeling approach

We present a coupled fluid-dynamic and electromagnetic model for volcanic ash plumes. In a forward approach, the model is able to simulate the plume dynamics from prescribed input flow conditions and generate the corresponding synthetic thermal infrared (TIR) image, allowing a comparison with field-based observations. An inversion procedure is then developed to retrieve vent conditions from TIR images, and to independently estimate the mass eruption rate.The adopted fluid-dynamic model is based on a one-dimensional, stationary description of a self-similar turbulent plume, for which an asymptotic analytical solution is obtained. The electromagnetic emission/absorption model is based on Schwarzschild's equation and on Mie's theory for disperse particles, and we assume that particles are coarser than the radiation wavelength (about 10μm) and that scattering is negligible. In the inversion procedure, model parameter space is sampled to find the optimal set of input conditions which minimizes the difference between the experimental and the synthetic image.Application of the inversion procedure to an ash plume at Santiaguito (Santa Maria volcano, Guatemala) has allowed us to retrieve the main plume input parameters, namely mass flow rate, initial radius, velocity, temperature, gas mass ratio, entrainment coefficient and their related uncertainty. Moreover, by coupling with the electromagnetic model we have been able to obtain a reliable estimate of the equivalent Sauter diameter of the total particle size distribution.The presented method is general and, in principle, can be applied to the spatial distribution of particle concentration and temperature obtained by any fluid-dynamic model, either integral or multidimensional, stationary or time-dependent, single or multiphase. The method discussed here is fast and robust, thus indicating potential for applications to real-time estimation of ash mass flux and particle size distribution, which is crucial for model-based forecasts of the volcanic ash dispersal process.

Magmatic storage conditions, decompression rate, and incipient caldera collapse of the 1902 eruption of Santa Maria Volcano, Guatemala

Phase equilibria experiments and analysis of natural pumice and phenocryst compositions indicate the 1902 Santa Maria dacite was stored at ~140–170MPa and 840–850°C prior to eruption. H2O-saturated, cold-seal experiments conducted in vessels with an intrinsic log fO2 of NNO+1±0.5 show that the natural phase assemblage (melt+plagioclase+amphibole+orthopyroxene+Fe–Ti oxides+apatite) is stable from approximately 115–140MPa at temperatures below ~825°C, to ~840–860°C at 150MPa, to >850 and <875°C at 200MPa. Natural plagioclase phenocrysts have rim compositions that range from An40–An45; this range of compositions defines a ~20°C band that intersects the stable phase assemblage at ~150MPa and 850°C. Plagioclase hosted melt inclusions were analyzed using FTIR and commonly contain <5wt.% H2O, which corresponds to a pressure of ~170MPa at 850°C, under pure H2O saturated conditions. Amphibole geothermobarometry (Ridolfi et al., 2010) applied to experimental samples suggest two populations of amphiboles, phenocrysts grown during the experiments and inherited xenocrysts, but the pressure–temperature conditions returned by the geothermobarometer are routinely >50MPa and >50°C greater than experimental run conditions; precise estimates of magmatic conditions based solely upon amphibole composition are likely inaccurate. The experimental results and analysis of natural crystals suggest that although the natural amphiboles likely record a broad range of magmatic conditions, only the lower bounds of that range reflect pre-eruptive storage conditions. Comparison of Santa Maria microlite abundances with decompression experiments examining other silicic systems from the literature suggests that the 1902 dacite decompressed at the rate of ~0.005 to 0.01MPa/s during the eruption. Applying the decompression rate with the previously described eruption rate of approximately 2–3×108kg/s (Williams and Self, 1983; Carey and Sparks, 1986) to the conduit model CONFLOW reveals that the eruption conduit was dike-like with an along-strike length >1km. Despite depositing ~20km3 of dacite tephra (equivalent to ~8.5km3 magma), the 1902 eruption did not form an obvious caldera. This work suggests that collapse of the dike-like conduit terminated the eruption, preventing full caldera collapse.

A detailed view into the eruption clouds of Santiaguito volcano, Guatemala, using Doppler radar

Using Doppler radar technology we are able to show that eruptions at Santiaguito volcano, Guatemala, are comprised of multiple explosive degassing pulses occurring at a frequency of 0.2 to 0.3 Hz. The Doppler radar system was installed about 2.7 km away from the active dome on the top of Santa Maria volcano. During four days of continuous measurement 157 eruptive events were recorded. The Doppler radar data reveals a vertical uplift of the dome surface of about 50 cm immediately prior to a first degassing pulse. Particle velocities range from 10 to 15 m/s (in the line of sight of the radar). In 80% of the observed eruptions a second degassing pulse emanates from the dome with significantly higher particle velocities (20–25 m/s again line of sight) and increased echo power, which implies an increase in mass flux. We carry out numerical experiments of ballistic particle transport and calculate corresponding synthetic radar signals. These calculations show that the observations are consistent with a pulsed release of material from the dome of Santiaguito volcano.

Mafic pyroclastic flows at Santa Maria (Gaua) Volcano, Vanuatu: the caldera formation problem in mainly mafic island arc volcanoes

ABSTRACTAt Santa Maria Volcano (New Hebrides island arc), extensive ash and scoria flow deposits overlie the mainly effusive, pre‐caldera cone. Hydromagmatic features characterize these deposits, the composition of juvenile clasts ranges from basalt to acid andesite/dacite (SiO2= 51–63.6%) with a dominant basaltic composition. The stratigraphic position of this pyroclastic series and its spatial distribution around a 8.5 km × 6 km wide caldera provide evidence of a relationship between this series and the caldera formation. In addition, these pyroclastic deposits are co‐genetic to parasitic cones and lava flows developed along faults concentric to the caldera. Both series result from a compositionally layered magma reservoir, the subordinate differentiated magmas being the result of fractional crystallization from the basalts. A model of caldera formation which implies a large hydromagmatic eruption at the central vent and minor magma withdrawal by flank eruptions is proposed. This model emphasizes the importance of mafic hydroclastic eruptions in the caldera forming event and contradicts a model implying only quiet subsidence, a process often proposed for the formation of calderas in island are volcanoes of mainly mafic composition.

Age and Magma Flux of Santa María Volcano, Guatemala: Correlation of Paleomagnetic Waveforms with the 28,000 to 25,000 yr B.P. Mono Lake Excursion

The United Nations has targeted Santa Maria volcano, Guatemala, as part of its multidisciplinary "Decade Volcano" program to mitigate volcanic hazards. As part of this program to spotlight one of the world's most dangerous volcanoes, and on the basis of paleomagnetic data, we represent a wholly new interpretation of the temporal evolution of the Santa María volcano. Santa María is a typical, moderate-sized (), basaltic-andesite stratovolcano. In 1902, a catastrophic Plinian eruption produced a crater in the south flank of the volcano exposing 250 m of interbedded lava flows, laharic material, and pyroclastic deposits comprising approximately 40% of the cone's infrastructure. A reanalysis of 25 block samples collected by Rose and co-workers and analysis of 48 cores from eight newly sampled lava flows reconfirms and refines the geomagnetic excursion. The resulting geomagnetic waveform is strongly correlatable with that of the 25 to 28 ka Mono Lake excursion. By inference, the latter 40% of the cone's volume () was emplaced in a 1000-3000 yr period with cone construction ending about 25 ka. The corresponding volcanic flux rate ranges from ; a range similar to young, active stratovolcanoes along the Central American arc. Extrapolating a flux of throughout the entire construction of Santa Maria suggests that cone growth began between 27.5-32.5 ka. However, up to of dacite tephra was ejected in the 1902 Plinian eruption, suggesting that the magma system feeding Santa Maria remained active during the past 25,000 yr. Assuming a geologically reasonable, constant flux rate of , a cumulative volume of nearly of magma could have been stored in the magma chamber)s) beneath Santa Maria. Because only of magma was erupted in 1902, as much as of magma, or its solidified complement, remains in situ in the crust. Thus the growth of even a moderate-sized volcano in Central America is complemented by voluminous intrusion of magma into the crust.

The October 1902 plinian eruption of Santa Maria volcano, Guatemala

The October, 1902, eruption of Santa Maria Volcano, Guatemala, was one of the largest this century. It was preceded by a great earthquake on April 19 centered at the volcano, as well as numerous other major earthquakes. The 18–20 hour-long plinian eruption on October 25 produced a column at least 28 km high, reaching well into the stratosphere. The airfall pumice deposit covered more than 1.2 million km 2 with a trace of ash and was only two meters thick at the vent. White dacitic pumice, dark gray scoriaceous basalt (with physically and chemically mixed intermediate pumice) and loose crystals of plagioclase, hornblende, hypersthene, biotite and magnetite make up the juvenile components of the deposit. Lithic fragments are of volcanic, plutonic, and metamorphic origin. The plinian deposit is a fine-grained, crystal-rich, single pumice fall unit and shows inverse grading. Mapping of the deposit gives a volume of 8.3 km 3 within the one mm isopach. Crystal concentration studies show that the true volume erupted was at least 20 km 3 (equivalent to 8.5 km 3 of dense dacite) and that 90% of the ejecta was less than 2 mm in diameter. The plinian volume eruption rate averaged 1.2 × 10 5 m 3s −1 and the average gas muzzle velocity of the column exceeded 270 ms −1. A total of 8.3 × 10 18 J of energy were released by the eruption. A knowledge of both theoretically derived eruption parameters and contemporary information allows a detailed analysis of eruption mechanisms. This eruption was the major stratospheric aerosol injection in the 1902–1903 period. However, mid- to low- latitude northern hemisphere temperature deviation data for the years following the eruption show no significant temperature decrease. This may be explained by the sulfur-poor nature of dacite magmas, suggesting that volatile composition, rather than mass of volatiles, is the controlling parameter in climatic response to explosive eruptions.

Effect of volcanic activity on fluvial-deltaic sedimentation in a modern arc-trench gap, southwestern Guatemala

The Pacific coastal plain in Central America forms the subaerial part of an arc-trench gap that is terminated as much as 60 km inland from the Pacific shoreline by the steep slopes of a row of active Quaternary volcanoes. The Samala fluvial-deltaic system, which heads inland from the volcanic arc, displays a combination of all of the Holocene features (frequently shifting braided channel, flanking elongate dendritically branched lakes, and a high-destructive wave-dominated arcuate delta) that characterize the coastal plain in southwestern Guatemala. Historical records indicate that the catastrophic eruption of Santa Maria Volcano in 1902 dramatically increased the amount of sediment supplied to the Samala River. Within a few years, deposition of sand and gravel raised the river bed 10 to 15 m, blocking the drainage of the river's tributaries to produce flanking lakes and allowing the river to easily shift its channel. Frequently, the braided system was diverted laterally into a flanking lake, interrupting deposition of organic-rich muds and locally filling the lake with prograding deltaic deposits. Continued channel shifting and aggradation of sand and gravel on the lower 25 km of the coastal plain have contributed to the growth of an elongate alluvial fan that probably originated during the Pleistocene. Contemporaneous with aggradation of the fluvial system, an elongate deltaic platform prograded about 7 km seaward, between 1902 and 1922, in response to the deposition of approximately 4 km3 of deltaic sediments. However, with waning sediment supply, the delta entered a destructive phase, and sands were redistributed laterally to prograding shoreface and beach environments, developing the present arcuate shoreline. The position of the arcuate shoreline has remained essentially unchanged since sometime before 1947; the volume of sediment derived from the active Santiaguito–Santa Maria volcanic complex and contributed to the shore zone by the Samala River has been sufficient, since that time, to prevent further shoreline retreat. A new constructive phase of deltation would begin in the event of another great eruption. Fluvial-deltaic sedimentation in arc-trench geologic settings, under conditions of torrential rainfall, differs significantly from fluvial-deltaic sedimentation in other geologic settings. This difference may be attributed to periodic catastrophic volcanic eruptions, which locally produce high-relief unvegetated slopes and allow extremely high local rates of erosion and subsequent fluvial-deltaic sedimentation.

Notes on the 1902 eruption of Santa María volcano, Guatemala

The first historic activity of Santa Maria volcano, Guatemala constituted one of the ten largest historic eruptions in the world, producing 5.5 km3 of debris. In hindsight, the six-month period before the October 1902 eruption was one of extremely abnormal seismicity in all of western Guatemala. The pyroclastis from the eruption were scattered widely over Western Guatemala and Southern Mexico and also caused world-wide atmospheric effects. The volcanics produced were of andesitic-dacitic composition, but there was wide variation from place to place in the sampled material — a fact apparently chiefly attributable to atmospheric-fractionation. There was apparently a change in chemistry of ash during the two-day eruption as well, the first, most voluminous ash was pumicious and white; later ash was finer, denser, darker, and slightly less silicious. The kinetic energy/thermal energy partition is determined to be similar to the value derived for Krakatoa,E k/E th ≅ 5.0 %. The thermal energy of the eruption was estimated at 4.2×1025 ergs. The explosion crater left on Santa Maria’s southwest flank after the eruption had a volume equal to less than 0.5 km3, a small fraction of the volume of material erupted. The two-day 1902 blast has greatly overshadowed subsequent activity; extrusion of the Santiaguito dome, which has occurred since 1922 in the explosion crater, has produced about 0.7 km3 of dacite lava and 1.6×1025 ergs of thermal energy in 48 years of activity.

Activity at Santa Maria volcano in Guatemala

Attention was again directed to the volcanic area of Central America and emphasis was laid on the opportunity presented in this region for carrying out a coordinated research on the problems of volcanology. The various volcanic centers are reasonably accessible and are not far removed from the laboratories that are interested in the analytical and synthetical phases of the problems. The manifestations are confined to a relatively small area and are sufficiently varied so that comparative studies can be made in the field. A fine opportunity therefore exists for coordinating work in the laboratory and in the field. All students interested in volcanological phenomena must admit that the study of volcanism is as yet only in the descriptive stage; there is no generally accepted theory to account for volcanic activity nor does an empirical background exist on which to base such a theory.