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USGS1986

Structural deformation and sedimentation in an active Caldera, Rabaul, Papua New Guinea

Recent seismic and tectonic activity in Rabaul Caldera, Papua New Guinea, suggests that magma is accumulating at a shallow depth beneath this partially submerged structure and that a new volcano may be developing. Changes in onshore elevation since 1971 (as much as 2 m on south Matupit Island) indicate that rapid and large-scale uplifts have occurred on the seafloor near the center of the caldera. The frequency of seismic events within the caldera has also increased during this period. Earthquake locations define an elliptical ring surrounding the center of this uplift within the caldera. A marine geophysical survey in 1982 by the U.S. Geological Survey's R/V "S.P. Lee" in Rabaul Caldera shows the development of a bulge in the seafloor near the center of the caldera. High-resolution seismic reflection profiles show that this bulge consists of two domal uplifts bounded and separated by two major north-south-trending fault zones. Deformed sediments overlie these zones; a prominent slump flanks the area of the bulge. Five major acoustic units were identified in the seismic reflection profiles: an acoustic basement and four sedimentary units consisting of irregularly layered, cross-layered, contorted, and well-layered sequences. The acoustic basement is probably composed of crystalline volcanic rocks, and the layered acoustic units are probably sediments, primarily ash deposited in different environments. The cross-layered, irregularly layered, and contorted units appear to have been deposited in a dynamic environment subjected to strong currents, seismicity, and/or mass wasting, while the well-layered units were deposited in a low-energy environment. Locally, well-layered sequences interfinger with the other sedimentary units, indicating a transitional environment that alternated between high-energy and low-energy depositional processes. A submarine channel cuts most of the acoustic units and appears to be the conduit for sediment transport out of the caldera; it occupies an older buried channel north of the caldera that is presently being exhumed. In the south, active erosion of well-layered sediments is taking place. What are believed to be several young volcanic cones also disrupt the depositional layers. We conclude that the bulge in the seafloor and the associated fault zones are a result of emplacement of magma at a shallow depth. Contorted sediment and slumps adjacent to the bulge are probably the result of uplift and seismic activity. The pattern of seismicity appears to reflect increased magma pressure at depth beneath the caldera floor. This activity may eventually lead to an eruption. ?? 1986.

Journal of Volcanology and Geothermal Research↗

USGS1989

Swift snowmelt and floods (lahars) caused by great pyroclastic surge at Mount St Helens volcano, Washington, 18 May 1980

The initial explosions at Mount St. Helens, Washington, on the moring of 18 May 1980 developed into a huge pyroclastic surge that generated catastrophic floods off the east and west flanks of the volcano. Near-source surge deposits on the east and west were lithic, sorted, lacking in accretionary lapilli and vesiculated ash, not plastered against upright obstacles, and hot enough to char wood - all attributes of dry pyroclastic surge. Material deposited at the surge base on steep slopes near the volcano transformed into high-concentration lithic pyroclastic flows whose deposits contain charred wood and other features indicating that these flows were hot and dry. Stratigraphy shows that even the tail of the surge had passed the east and west volcano flanks before the geomorphically distinct floods (lahars) arrived. This field evidence undermines hypotheses that the turbulent surge was itself wet and that its heavy components segregated out to transform directly into lahars. Nor is there evidence that meters-thick snow-slab avalanches intimately mixed with the surge to form the floods. The floods must have instead originated by swift snowmelt at the base of a hot and relatively dry turbulent surge. Impacting hot pyroclasts probably transferred downslope momentum to the snow surface and churned snow grains into the surge base. Melting snow and accumulating hot surge debris may have moved initially as thousands of small thin slushflows. As these flows removed the surface snow and pyroclasts, newly uncovered snow was partly melted by the turbulent surge base; this and accumulating hot surge debris in turn began flowing, a self-sustaining process feeding the initial flows. The flows thus grew swiftly over tens of seconds and united downslope into great slushy ejecta-laden sheetfloods. Gravity accelerated the floods to more than 100 km/h as they swept down and off the volcano flanks while the snow component melted to form great debris-rich floods (lahars) channeled into valleys. ?? 1989 Springer-Verlag.

Bulletin of Volcanology↗

USGS2008

Objective rapid delineation of areas at risk from block-and-ash pyroclastic flows and surges

Assessments of pyroclastic flow (PF) hazards are commonly based on mapping of PF and surge deposits and estimations of inundation limits, and/or computer models of varying degrees of sophistication. In volcanic crises a PF hazard map may be sorely needed, but limited time, exposures, or safety aspects may preclude fieldwork, and insufficient time or baseline data may be available for reliable dynamic simulations. We have developed a statistically constrained simulation model for block-and-ash type PFs to estimate potential areas of inundation by adapting methodology from Iverson et al. (Geol Soc America Bull 110:972-984, (1998) for lahars. The predictive equations for block-and-ash PFs are calibrated with data from several volcanoes and given by A = (0.05 to 0.1) V 2/3 , B = (35 to 40) V 2/3 , where A is cross-sectional area of inundation, B is planimetric area and V is deposit volume. The proportionality coefficients were obtained from regression analyses and comparison of simulations to mapped deposits. The method embeds the predictive equations in a GIS program coupled with DEM topography, using the LAHARZ program of Schilling (1998). Although the method is objective and reproducible, any PF hazard zone so computed should be considered as an approximate guide only, due to uncertainties on the coefficients applicable to individual PFs, the authenticity of DEM details, and the volume of future collapses. The statistical uncertainty of the predictive equations, which imply a factor of two or more in predicting A or B for a specified V, is superposed on the uncertainty of forecasting V for the next PF to descend a particular valley. Multiple inundation zones, produced by simulations using a selected range of volumes, partly accommodate these uncertainties. The resulting maps show graphically that PF inundation potentials are highest nearest volcano sources and along valley thalwegs, and diminish with distance from source and lateral distance from thalweg. The model does not explicitly consider dynamic behavior, which can be important. Ash-cloud surge impact limits must be extended beyond PF hazard zones and we provide several approaches to do this. The method has been used to supply PF and surge hazard maps in two crises: Merapi 2006; and Montserrat 2006-2007. Springer-Verlag 2008.

Bulletin of Volcanology↗

USGS2020

Local magnitude, coda magnitude, and radiated energy of volcanic tectonic earthquakes from October 2010 to December 2011 at Sinabung volcano, Indonesia

In August 2010, Sinabung volcano began erupting after more than a thousand years of dormancy. Following several weeks of phreatic eruptions, the eruptions ceased and Sinabung entered what became an inter-eruptive period of dominantly seismic unrest. While standard equations for understanding the size of an earthquake (local magnitude (M L ), coda magnitude (M C ), and seismic energy release (E R )) have long been developed, it is best practice to fine tune these relations for a given region and period of study to more accurately describe seismicity and to directly compare it with other volcanic systems. More accurate descriptions of magnitudes and energy release are vital to accurate volcanic eruption forecasting and evaluation of seismic and volcanic risk. In this study, we use high-frequency volcano-tectonic (VT) earthquakes recorded on a temporary three-component network installed between October 2010 and December 2011 in the region around Sinabung volcano to better constrain the seismic parameters of and better understand this previously unstudied volcano. We determine region-specific formulas for M L , M C , and E R as follows: M L = log 10 A + 1.1252 log 10 r + 0.0280 r − 2.5427 , M C = 0.7764 log 10 t c o d a + 0.0676 r − 0.7185 , a n d log 10 ( E R ) = 1.5720 M L + 11.5258 , where A , r , and t coda are maximum amplitude on a Wood-Anderson seismogram, hypocentral distance (km), and the coda duration (s), respectively. Constants in the M L equation have physically interpretable meanings. The constant for the geometrical spreading term (log 10 r term) equals one for perfect spherical spreading of the waveform. Our value is greater than one and thus suggests that wavefronts spread at a slightly different rate than for simple spherical spreading. The constant for the attenuation term ( r term) is consistent with locally mapped attenuative deposits (limestones and tuffs) and previous 3D tomographic results. Our M C equation differs from a previous study, likely because different data in a different time period were used. Earthquake hypocenters are consistent with those located in previous tomographic studies, and we interpret the earthquakes in this study as distal VT earthquakes induced by continued magmatic intrusion at Sinabung over the period of October 2010–December 2011.

Sinabung volcano↗

USGS2006

Multiple edifice-collapse events in the Eastern Mexican Volcanic Belt: The role of sloping substrate and implications for hazard assessment

The Citlalte??petl-Cofre de Perote volcanic chain forms an important physiographic barrier that separates the Central Altiplano (2500??masl) from the Gulf Coastal Plain (GCP) (1300??masl). The abrupt eastward drop in relief between these provinces gives rise to unstable conditions and consequent gravitational collapse of large volcanic edifices built at the edge of the Altiplano. Eastward sloping substrate, caused by the irregular configuration of the basement rocks, is the dominant factor that controls the direction of collapsing sectors in all major volcanoes in the region to be preferentially towards the GCP. These collapses produced voluminous debris avalanches and lahars that inundated the well-developed drainages and clastic aprons that characterize the Coastal Plain. Large catastrophic collapses from Citlalte??petl, Las Cumbres, and Cofre de Perote volcanoes are well documented in the geologic record. Some of the avalanches and transformed flows have exceptionally long runouts and reach the Gulf of Mexico traveling more than 120??km from their source. So far, no direct evidence has been found for magmatic activity associated with the initiation of these catastrophic flank-collapses. Apparently, instability of the volcanic edifices has been strongly favored by very intense hydrothermal alteration, abrupt topographic change, and intense fracturing. In addition to the eastward slope of the substrate, the reactivation of pre-volcanic basement structures during the Late Tertiary, and the E-W to ENE-SSW oriented regional stress regimes may have played an important role in the preferential movement direction of the avalanches and flows. In addition to magmatic-hydrothermal processes, high amounts of rainfall in the area is another factor that enhances alteration and eventually weakens the rocks. It is very likely that seismic activity may be the principal triggering mechanism that caused the flank collapse of large volcanic edifices in the Eastern Mexican Volcanic Belt. However, critical pore water pressure from extraordinary amounts of rainfall associated with hurricanes or other meteorological perturbation cannot be ruled out, particularly for smaller volume collapses. There are examples in the area of small seismogenic debris flows that have occurred in historical times, showing that these processes are not uncommon. Assessing the stability conditions of major volcanic edifices that have experienced catastrophic sector collapses is crucial for forecasting future events. This is particularly true for the Eastern Mexican Volcanic Belt, where in many cases no magmatic activity was associated with the collapse. Therefore, edifice failure could occur again without any precursory warning. ?? 2006 Elsevier B.V. All rights reserved.

Journal of Volcanology and Geothermal Research↗

USGS2018

Towards coordinated regional multi-satellite InSAR volcano observations: Results from the Latin America pilot project

Within Latin America, about 319 volcanoes have been active in the Holocene, but 202 of these volcanoes have no seismic, deformation or gas monitoring. Following the 2012 Santorini Report on satellite Earth Observation and Geohazards, the Committee on Earth Observation Satellites (CEOS) developed a 4-year pilot project (2013-2017) to demonstrate how satellite observations can be used to monitor large numbers of volcanoes cost-effectively, particularly in areas with scarce instrumentation and/or difficult access. The pilot aims to improve disaster risk management (DRM) by working directly with the volcano observatories that are governmentally responsible for volcano monitoring as well as with the international space agencies (ESA, CSA, ASI, DLR, JAXA, NASA, CNES). The goal is to make sure that the most useful data are collected at each volcano following the guidelines of the Santorini report that observation frequency is related to volcano activity, and to communicate the results to the local institutions in a timely fashion. Here we highlight how coordinated multi-satellite observations have been used by volcano observatories to monitor volcanoes and respond to crises. Our primary tool is measurements of ground deformation made by Interferometric Synthetic Aperture Radar (InSAR), which have been used in conjunction with other observations to determine the alert level at these volcanoes, served as an independent check on ground sensors, guided the deployment of ground instruments, and aided situational awareness. During this time period, we find 26 volcanoes deforming, including 18 of the 28 volcanoes that erupted - those eruptions without deformation were less than 2 on the VEI scale. Another 7 volcanoes were restless and the volcano observatories requested satellite observations, but no deformation was detected. We describe the lessons learned about the data products and information that are most needed by the volcano observatories in the different countries using information collected by questionnaires. We propose a practical strategy for regional to global satellite volcano monitoring for use by volcano observatories in Latin America and elsewhere to realize the vision of the Santorini report.

Journal of Applied Volcanology↗

USGS2021

Volcanic seismicity beneath Chuginadak Island, Alaska (Cleveland and Tana volcanoes): Implications for magma dynamics and eruption forecasting

Cleveland and Tana are remote volcanoes located in the central Aleutian volcanic arc on the eastern end of the Islands of Four Mountains (IFM). The persistently active Mount Cleveland volcano, on the western side of Chuginadak Island, is surrounded by several closely spaced Quaternary volcanic centers including Carlisle, Herbert, Kagamil, Tana, and Uliaga, and numerous small satellite vents on Chiginadak between Cleveland and Tana. The Alaska Volcano Observatory (AVO) installed two permanent broadband seismometers on Chuginadak Island in 2014, and we operated a temporary broadband network focused on the western side of the island in 2015–2016. Collectively, these stations provided the first seismic observations of this frequently active volcano and the surrounding Holocene-aged volcanic vents. During the study period (July 2014–January 2019), eruptive activity at Cleveland was characterized by small explosions separated by periods of lava effusion that formed small domes in the volcano's summit crater. We characterize seismicity beneath Chuginadak Island through automated analysis of event waveform frequency content, development of a one-dimensional P-wave velocity model, calculation of earthquake hypocenters, magnitudes, focal mechanisms, and identification of earthquake families. This analysis reveals the full range of seismic event types expected in a highly active volcanic environment and includes Volcano-Tectonic (VT) earthquakes, Long-Period (LP) events, and explosion signals. LP events appear to cluster at shallow depth beneath the active crater of Mount Cleveland and almost all of the explosions occur without identifiable short-term (hours to days) seismic precursors. VT earthquakes beneath Mount Cleveland occur at depths of 2 to 8 km below sea level (BSL) and range in magnitude from −0.2 to 1.8. VT focal mechanisms have horizontal P-axes that align with the regional axis of maximum stress. These observations, and a relatively slow one-dimensional seismic velocity model, are consistent with a shallow body of magma that is fed through a deeper conduit system. The time-history of VT earthquakes and shallow LP events suggest their occurrence may track the transfer of magma and fluids from the mid-crust to the shallow portions of the conduit system and may provide a means to anticipate future explosions and periods of dome growth. VT hypocenters also extend ~7 km northeast of Cleveland's summit at depths of 5 to 10 km BSL, under a group of Holocene-aged vents between Mount Cleveland and Tana. These earthquakes have vertically-oriented P-axes and a greater percentage occur in families. These observations, combined with observations of vent orientation and morphology and gas flux, suggest the area between Cleveland and Tana represents a zone of complicated volcano-tectonic interaction, similar to calderas elsewhere in the Aleutian arc. The presence of a larger volcanic system in the eastern IFM could influence magmatism and account for the multiple closely spaced volcanic centers in this region.

Alaska↗

USGS2006

Isotope geochemistry of early Kilauea magmas from the submarine Hilina bench: The nature of the Hilina mantle component

Submarine lavas recovered from the Hilina bench region, offshore Kilauea, Hawaii Island provide information on ancient Kilauea volcano and the geochemical components of the Hawaiian hotspot. Alkalic lavas, including nephelinite, basanite, hawaiite, and alkali basalt, dominate the earliest stage of Kilauea magmatism. Transitional basalt pillow lavas are an intermediate phase, preceding development of the voluminous tholeiitic subaerial shield and submarine Puna Ridge. Most alkalic through transitional lavas are quite uniform in Sr–Nd–Pb isotopes, supporting the interpretation that variable extent partial melting of a relatively homogeneous source was responsible for much of the geochemical diversity of early Kilauea magmas ( Sisson et al., 2002 ). These samples are among the highest 206 Pb/ 204 Pb known from Hawaii and may represent melts from a distinct geochemical and isotopic end-member involved in the generation of most Hawaiian tholeiites. This end-member is similar to the postulated literature Kea component, but we propose that it should be renamed Hilina, to avoid confusion with the geographically defined Kea-trend volcanoes. Isotopic compositions of some shield-stage Kilauea tholeiites overlap the Hilina end-member but most deviate far into the interior of the isotopic field defined by magmas from other Hawaiian volcanoes, reflecting the introduction of melt contributions from both “Koolau” (high 87 Sr/ 86 Sr, low 206 Pb/ 204 Pb) and depleted (low 87 Sr/ 86 Sr, intermediate 206 Pb/ 204 Pb) source materials. This shift in isotopic character from nearly uniform, end-member, and alkalic, to diverse and tholeiitic corresponds with the major increase in Kilauea's magmatic productivity. Two popular geodynamic models can account for these relations: (1) The upwelling mantle source could be concentrically zoned in both chemical/isotopic composition, and in speed/extent of upwelling, with Hilina (and Loihi) components situated in the weakly ascending margins and the Koolau component in the interior. The depleted component could be refractory and spread throughout or scavenged from the overlying lithosphere. (2) The Hilina (and Loihi) components could be a more fertile material (lower melting temperature) spread irregularly throughout the Hawaiian source in a matrix of more refractory depleted and Koolau compositions. Modest upwelling along the leading hotspot margin melts the fertile domains predominantly, while the refractory matrix also partially melts in the more vigorously upwelling hotspot interior, diluting the Hilina and Loihi components and yielding voluminous isotopically diverse tholeiitic magmas.

Hawai'i↗

USGS2024

Special topic—Unoccupied aircraft systems

Introduction Unoccupied aircraft systems (UAS) increasingly support volcano monitoring and eruption response activities in the United States and abroad (James and others, 2020). Advances in UAS platforms and miniaturization of sensors over the past decade have expanded the use of this technology for a wide range of applications within volcanology (Jordan, 2019; James and others, 2020). UAS can greatly enhance existing ground-, aerial-, and satellite-based observation and in situ monitoring networks at volcanoes by providing new avenues for data collection in terms of access, resolution, and timing. UAS can collect data in difficult and hazardous environments, reducing risk to occupied aircraft and (or) ground crews; support the generation of dense time series of data through frequent, low-cost, high-resolution surveys; and provide real-time, on-demand measurements at volcanic systems for indicators such as gas, thermal output, and topographic change without the need to wait for contracted aerial flight services or satellite orbit intervals. During the 2018 response to the Kīlauea eruption on the Island of Hawaiʻi, UAS were used extensively and successfully to monitor, track, investigate, and (or) warn of ongoing volcanic activity (fig. L1; Neal and others, 2019). Throughout the eruption, the UAS team was able to provide data products rapidly to emergency managers for situational awareness and to scientists for quantitative hazard assessment (Diefenbach and others, 2018). Over the course of 4 months, more than 1,200 UAS missions were flown and yielded critical data that included (1) live video to emergency operations centers in Hilo and Honolulu for situational awareness; (2) gas emission rates, compositions, and concentrations; (3) repeat nadir videos over sections of the lava channel to support measurements of lava effusion rate; (4) oblique videos for hazards assessment and outreach; and (5) photogrammetry surveys to create very high-resolution topographic models and orthophoto mosaics (Diefenbach and others, 2018). In coming years, the U.S. Geological Survey (USGS) Volcano Hazards Program (VHP) plans to expand its fleet of UAS, associated sensors, and remote pilots to enhance volcano monitoring and response capabilities. Currently (2023), USGS operational capabilities are restricted to small class UAS (sUAS; less than [<] 55 pounds) that are limited in range, payload capacity, and flight duration. Additionally, USGS-piloted platforms are restricted to the U.S. Department of the Interior Office of Aviation Services approved fleet, which includes a limited number of small and medium multi-rotor aircraft and vertical take-off and landing fixed-wing aircraft ( https://www.doi.gov/aviation/uas/fleet ). Each type of platform has advantages and disadvantages. Small rotor-wing quadcopters are fast to deploy, can be carried in a backpack, and are highly maneuverable, but are typically only equipped with a small camera and have a minimal flight range. Medium rotor-wing hexacopters can carry larger payloads (< 20 kilograms [kg]) and varied sensors, but, with the drawback of minimal flight time (<30 minutes), they typically have similar range capabilities to their smaller counterparts and are not as easily deployable. Fixed-wing platforms provide relatively long endurance (<60 minutes) and range and, with the vertical take-off and landing capabilities, can launch and land in relatively small spaces; however, they have less maneuverability and hovering capability than the rotor-wing platforms. Although the 2018 Kīlauea response showed the benefit of the current UAS fleet, all platforms have limited range [<10 kilometers (km)], such that operators must be stationed relatively close to the region of interest. To expand UAS monitoring capabilities, VHP staff have been working closely with industry partners and the National Aeronautics and Space Administration to develop a next-generation UAS for volcano monitoring (Kern and others, 2020). This ruggedized, mid-range (>20 km), multiparametric (gas and photogrammetry) UAS has been developed to meet volcano monitoring needs, particularly at less accessible, more dangerous stratovolcanoes. It is expected in the coming years that additional UAS platforms with new and smaller sensors will expand our capabilities to meet the Nation’s volcano monitoring objectives.

Scientific Investigations Report↗

USGS2013

Evaluation of Redoubt Volcano's sulfur dioxide emissions by the Ozone Monitoring Instrument

The 2009 eruption of Redoubt Volcano, Alaska, provided a rare opportunity to compare satellite measurements of sulfur dioxide (SO 2 ) by the Ozone Monitoring Instrument (OMI) with airborne SO 2 measurements by the Alaska Volcano Observatory (AVO). Herein we: (1) compare OMI and airborne SO 2 column density values for Redoubt's tropospheric plume, (2) calculate daily SO 2 masses from Mount Redoubt for the first three months of the eruption, (3) develop simple methods to convert daily measured SO 2 masses into emission rates to allow satellite data to be directly integrated with the airborne SO 2 emissions dataset, (4) calculate cumulative SO 2 emissions from the eruption, and (5) evaluate OMI as a monitoring tool for high-latitude degassing volcanoes. A linear correlation (R 2 ~ 0.75) is observed between OMI and airborne SO 2 column densities. OMI daily SO 2 masses for the sample period ranged from ~ 60.1 kt on 24 March to below detection limit, with an average daily SO 2 mass of ~ 6.7 kt. The highest SO 2 emissions were observed during the initial part of the explosive phase and the emissions exhibited an overall decreasing trend with time. OMI SO 2 emission rates were derived using three methods and compared to airborne measurements. This comparison yields a linear correlation (R 2 ~ 0.82) with OMI-derived emission rates consistently lower than airborne measurements. The comparison results suggest that OMI's detection limit for high latitude, springtime conditions varies from ~ 2000 to 4000 t/d. Cumulative SO 2 masses calculated from daily OMI data for the sample period are estimated to range from 542 to 615 kt, with approximately half of this SO 2 produced during the explosive phase of the eruption. These cumulative masses are similar in magnitude to those estimated for the 1989–90 Redoubt eruption. Strong correlations between daily OMI SO 2 mass and both tephra mass and acoustic energy during the explosive phase of the eruption suggest that OMI data may be used to infer relative eruption size and explosivity. Further, when used in conjunction with complementary datasets, OMI daily SO 2 masses may be used to help distinguish explosive from effusive activity and identify changes in lava extrusion rates. The results of this study suggest that OMI is a useful volcano monitoring tool to complement airborne measurements, capture explosive SO 2 emissions, and provide high temporal resolution SO 2 emissions data that can be used with interdisciplinary datasets to illuminate volcanic processes.

Alaska↗

USGS1991

Fossil and active fumaroles in the 1912 eruptive deposits, Valley of ten thousand smokes, Alaska

Fumaroles in the ash-flow sheet emplaced during the 1912 eruption of Novarupta were intensely active throughout the Valley of Ten Thousand Smokes (VTTS) when first studied in 1917. Fumarole temperatures recorded in 1919 were as hot as 645??C. Influx of surface waters into the hot ash-flow sheet provided the fluid flow to sustain the fumaroles but also enhanced cooling so that by the mid-1930's vigorous activity survived only in the vent region. Configuration and distribution of high-temperature fissure fumaroles tens of meters long, that are prevalent in the middle and upper VTTS, were controlled largely by sintering and degree of welding, which in turn controlled fracturing and permeability of the ash-flow tuff. One fracture type developed parallel to the enclosing valley walls during compaction of the ash-flow sheet. Another type extends across the VTTS nearly perpendicular to the flow direction. A third type of randomly oriented fractures developed as cooling contraction cracks during vapor-phase devitrification. In distal parts of the ash-flow sheet where the tuff is nonwelded, prominent fumaroles have irregular funnel-shaped morphologies. Fumarole distribution in the nonwelded part of the ash-flow sheet is concentrated above pre-emplacement river channels. The hottest, longest-lived fumaroles occurred in the upper VTTS near the 1912 vent where the ash-flow sheet is thicker, more indurated, and on average more mafic (richer in dacite and andesite) in contrast to the thinner, nonwelded rhyolitic tuff in the distal part of the sheet. Fumarolic activity was less intense in the distal part of the tuff because of lower emplacement temperatures, more diffuse fumarole conduits in the nonwelded tuff, and the thinness of the ash-flow sheet. Chemical leaching of ash-flow tuff by hot rising fluids took place adjacent to fumarolic conduits in deep parts of the fumaroles. Deposition of incrustation minerals, the components of which were carried upward by fumarolic gases, took place in the upper part of the ejecta, mostly in the fallout layers. The permeability difference between the ash-flow tuff and the overlying coarse dacite fallout was a critical factor in promoting the abrupt gradients in temperature, pressure, and fO2 that resulted in deposition of minerals from the fumarolic gases. The permeability difference between nonwelded ash-flow tuff and overlying fine-grained fall layers in the lower VTTS is less pronounced. The total mass of fumarolically deposited minerals appears large at first glance owing to the conspicuous coloration by Fe minerals; the mass is appreciably less than is apparent, however, because most incrustations are composed largely of ejecta coated or cemented by fine-grained fumarolic minerals. A large mass of unstable incrustation minerals, mainly chlorides and sulfates, reported during the 1917-1919 studies have since been removed by dissolution and weathering. In the vent region, argillic alteration that followed high-temperature degassing is localized along arcuate subsidence fractures in fallback ejecta. At widely scattered residual orifices, fumarolic gases presently are near-neutral steam, and temperatures are as hot as 90??C. ?? 1991.

Journal of Volcanology and Geothermal Research↗

USGS2017

Magmatic degassing, lava dome extrusion, and explosions from Mount Cleveland volcano, Alaska, 2011–2015: Insight into the continuous nature of volcanic activity over multi-year timescales

Mount Cleveland volcano (1730 m) is one of the most active volcanoes in the Aleutian arc, Alaska, but heightened activity is rarely accompanied by geophysical signals, which makes interpretation of the activity difficult. In this study, we combine volcanic gas emissions measured for the first time in August 2015 with longer-term measurements of thermal output and lava extrusion rates between 2011 and 2015 calculated from MODIS satellite data with the aim to develop a better understanding of the nature of volcanic activity at Mount Cleveland. Degassing measurements were made in the month following two explosive events (21 July and 7 August 2015) and during a period of new dome growth in the summit crater. SO 2 emission rates ranged from 400 to 860 t d − 1 and CO 2 /SO 2 ratios were < 3, consistent with the presence of shallow magma in the conduit and the observed growth of a new lava dome. Thermal anomalies derived from MODIS data from 2011 to 2015 had an average repose time of only 4 days, pointing to the continuous nature of volcanic activity at this volcano. Rapid increases in the cumulative thermal output were often coincident with visual confirmation of dome growth or accumulations of tephra in the crater. The average rate of lava extrusion calculated for 9 periods of rapid increase in thermal output was 0.28 m 3 s − 1 , and the total volume extruded from 2011 to 2015 was 1.9–5.8 Mm 3 . The thermal output from the lava extrusion events only accounts for roughly half of the thermal budget, suggesting a continued presence of shallow magma in the upper conduit, likely driven by convection. Axisymmetric dome morphology and occasional drain back of lava into the conduit suggests low-viscosity magmas drive volcanism at Mount Cleveland. It follows also that only small overpressures can be maintained given the small domes and fluid magmas, which is consistent with the low explosivity of most of Mount Cleveland's eruptions. Changes between phases of dome growth and explosive activity are somewhat unpredictable and likely result from plugs that are related to the dome obtaining a critical dimension, or from small variations in the magma ascent rate that lead to crystallization-induced blockages in the upper conduit, thereby reducing the ability of magma to degas. We suggest the small magma volumes, slow ascent rates, and low magma viscosity lead to the overall lack of anomalous geophysical signals prior to eruptions, and that more continuous volcanic degassing measurements might lead to more successful eruption forecasting at this continuously-active open-vent volcano.

Alaska↗

USGS2017

Plateaus and sinuous ridges as the fingerprints of lava flow inflation in the Eastern Tharsis Plains of Mars

The Tharsis Montes rift aprons are composed of outpourings of lava from chaotic terrains to the northeast and southwest flank of each volcano. Sinuous and branching channel networks that are present on the rift aprons suggest the possibility of fluvial processes in their development, or erosion by rapidly emplaced lavas, but the style of lava flow emplacement throughout rift apron development is not clearly understood. To better characterize the style of lava emplacement and role of fluvial processes in rift apron development, we conducted morphological mapping of the Pavonis Mons southwest rift apron and the eastern Tharsis plains using images from the High Resolution Imaging Science Experiment (HiRISE), Mars Orbiter Camera (MOC), Context Camera (CTX), Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) along with the Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Records (PEDRs) and gridded data. Our approach was to: (1) search for depositional fans at the slope break between the rift apron and adjacent low slope plains; (2) determine if there is evidence that previously formed deposits might have been buried by plains units; (3) characterize the Tharsis plains morphologies east of Pavonis Mons; and (4) assess their relationship to the rift apron units. We have not identified topographically significant depositional fans, nor did we observe evidence to suggest that plains units have buried older rift apron units. Flow features associated with the rift apron are observed to continue across the slope break onto the plains. In this area, the plains are composed of a variety of small fissures and low shield vents around which broad channel-fed and tube-fed flows have been identified. We also find broad, flat-topped plateaus and sinuous ridges mixed among the channels, tubes and vents. Flat-topped plateaus and sinuous ridges are morphologies that are analogous to those observed on the coastal plain of Hawai‘i, where lava flows have advanced from the volcano's several degree flank onto the nearly zero degree coastal plain. When local volumetric flow rates are low, flow fronts tend to spread laterally and often thicken via endogenous growth, or inflation, of the sheet-like flow units. If flow advance is restricted by existing topography into narrow pathways, inflation can be focused into sinuous, elongate ridges. The presence of plateaus and ridges—emplaced from the rift zones, across the plains to the east of Pavonis Mons—and a lack of fan-like features, or evidence for their burial, are consistent with rift apron lavas crossing a slope break with low local volumetric flow rates that led to inflation of sheet-like and tube-fed lava flows.

Journal of Volcanology and Geothermal Research↗

USGS2009

Is the track of the Yellowstone hotspot driven by a deep mantle plume? - Review of volcanism, faulting, and uplift in light of new data

Geophysical imaging of a tilted mantle plume extending at least 500 km beneath the Yellowstone caldera provides compelling support for a plume origin of the entire Yellowstone hotspot track back to its inception at 17 Ma with eruptions of flood basalts and rhyolite. The widespread volcanism, combined with a large volume of buoyant asthenosphere, supports a plume head as an initial phase. Estimates of the diameter of the plume head suggest it completely spanned the upper mantle and was fed from sources beneath the transition zone, We consider a mantle–plume depth to at least 1,000 km to best explain the large scale of features associated with the hotspot track. The Columbia River–Steens flood basalts form a northward-migrating succession consistent with the outward spreading of a plume head beneath the lithosphere. The northern part of the inferred plume head spread (pancaked) upward beneath Mesozoic oceanic crust to produce flood basalts, whereas basalt melt from the southern part intercepted and melted Paleozoic and older crust to produce rhyolite from 17 to 14 Ma. The plume head overlapped the craton margin as defined by strontium isotopes; westward motion of the North American plate has likely “scraped off” the head from the plume tail. Flood basalt chemistries are explained by delamination of the lithosphere where the plume head intersected this cratonic margin. Before reaching the lithosphere, the rising plume head apparently intercepted the east-dipping Juan de Fuca slab and was deflected ~ 250 km to the west; the plume head eventually broke through the slab, leaving an abruptly truncated slab. Westward deflection of the plume head can explain the anomalously rapid hotspot movement of 62 km/m.y. from 17 to 10 Ma, compared to the rate of ~ 25 km/m.y. from 10 to 2 Ma. A plume head-to-tail transition occurred in the 14-to-10-Ma interval in the central Snake River Plain and was characterized by frequent (every 200–300 ka for about 2 m.y. from 12.7 to 10.5 Ma) “large volume (> 7000 km 3 )”, and high temperature rhyolitic eruptions (> 1000 °C) along a ~ 200–km-wide east–west band. The broad transition area required a heat source of comparable area. Differing characteristics of the volcanic fields here may in part be due to variations in crustal composition but also may reflect development in differing parts of an evolving plume where the older fields may reflect the eruption from several volcanic centers located above very large and extensive rhyolitic magma chamber(s) over the detached plume head while the younger fields may signal the arrival of the plume tail intercepting and melting the lithosphere and generating a more focused rhyolitic magma chamber. The three youngest volcanic fields of the hotspot track started with large ignimbrite eruptions at 10.21, 6.62, and 2.05 Ma. They indicate hotspot migration N55° E at ~ 25 km/m.y. compatible in direction and velocity with the North American Plate motion. The Yellowstone Crescent of High Terrain (YCHT) flares outward ahead of the volcanic progression in a pattern similar to a bow-wave, and thus favors a sub-lithospheric driver. Estimates of YCHT-uplift rates are between 0.1 and 0.4 mm/yr. Drainage divides have migrated northeastward with the hotspot. The Continental Divide and a radial drainage pattern now centers on the hotspot. The largest geoid anomaly in the conterminous U.S. is also centered on Yellowstone and, consistent with uplift above a mantle plume. Bands of late Cenozoic faulting extend south and west from Yellowstone. These bands are subdivided into belts based both on recency of offset and range-front height. Fault history within these belts suggests the following pattern: Belt I — starting activity but little accumulated offset; Belt II — peak activity with high total offset and activity younger than 14 ka; Belt III — waning activity with large offset and activity younger than 140 ka; and Belt IV — apparently dead on substantial range fronts (south side of the eastern Snake River Plain only). These belts of fault activity have migrated northeast in tandem with the adjacent hotspot volcanism. On the southern arm of the YCHT, fault activity occurs on the inner, western slope consistent with driving by gravitational potential energy, whereas faulting has not started on the eastern, outer, more compressional slope. Range fronts increase in height and steepness northeastward along the southern-fault band. Both the belts of faulting and the YCHT are asymmetrical across the volcanic hotspot track, flaring out 1.6 times more on the south than the north side. This and the southeast tilt of the Yellowstone plume may reflect southeast flow of the upper mantle.

Wyoming↗

USGS1983

Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.

New investigations of the geology of Crater Lake National Park necessitate a reinterpretation of the eruptive history of Mount Mazama and of the formation of Crater Lake caldera. Mount Mazama consisted of a glaciated complex of overlapping shields and stratovolcanoes, each of which was probably active for a comparatively short interval. All the Mazama magmas apparently evolved within thermally and compositionally zoned crustal magma reservoirs, which reached their maximum volume and degree of differentiation in the climactic magma chamber ∼ 7000 yr B.P. The history displayed in the caldera walls begins with construction of the andesitic Phantom Cone ∼ 400,000 yr B.P. Subsequently, at least 6 major centers erupted combinations of mafic andesite, andesite, or dacite before initiation of the Wisconsin Glaciation ∼ 75,000 yr B.P. Eruption of andesitic and dacitic lavas from 5 or more discrete centers, as well as an episode of dacitic pyroclastic activity, occurred until ∼ 50,000 yr B.P.; by that time, intermediate lava had been erupted at several short-lived vents. Concurrently, and probably during much of the Pleistocene, basaltic to mafic andesitic monogenetic vents built cinder cones and erupted local lava flows low on the flanks of Mount Mazama. Basaltic magma from one of these vents, Forgotten Crater, intercepted the margin of the zoned intermediate to silicic magmatic system and caused eruption of commingled andesitic and dacitic lava along a radial trend sometime between ∼ 22,000 and ∼ 30,000 yr B.P. Dacitic deposits between 22,000 and 50,000 yr old appear to record emplacement of domes high on the south slope. A line of silicic domes that may be between 22,000 and 30,000 yr old, northeast of and radial to the caldera, and a single dome on the north wall were probably fed by the same developing magma chamber as the dacitic lavas of the Forgotten Crater complex. The dacitic Palisade flow on the northeast wall is ∼ 25,000 yr old. These relatively silicic lavas commonly contain traces of hornblende and record early stages in the development of the climatic magma chamber. Some 15,000 to 40,000 yr were apparently needed for development of the climactic magma chamber, which had begun to leak rhyodacitic magma by 7015 ± 45 yr B.P. Four rhyodacitic lava flows and associated tephras were emplaced from an arcuate array of vents north of the summit of Mount Mazama, during a period of ∼ 200 yr before the climactic eruption. The climactic eruption began 6845 ± 50 yr B.P. with voluminous airfall deposition from a high column, perhaps because ejection of ∼ 4−12 km 3 of magma to form the lava flows and tephras depressurized the top of the system to the point where vesiculation at depth could sustain a Plinian column. Ejecta of this phase issued from a single vent north of the main Mazama edifice but within the area in which the caldera later formed. The Wineglass Welded Tuff of Williams (1942) is the proximal featheredge of thicker ash-flow deposits downslope to the north, northeast, and east of Mount Mazama and was deposited during the single-vent phase, after collapse of the high column, by ash flows that followed topographic depressions. Approximately 30 km 3 of rhyodacitic magma were expelled before collapse of the roof of the magma chamber and inception of caldera formation ended the single-vent phase. Ash flows of the ensuing ring-vent phase erupted from multiple vents as the caldera collapsed. These ash flows surmounted virtually all topographic barriers, caused significant erosion, and produced voluminous deposits zoned from rhyodacite to mafic andesite. The entire climactic eruption and caldera formation were over before the youngest rhyodacitic lava flow had cooled completely, because all the climactic deposits are cut by fumaroles that originated within the underlying lava, and part of the flow oozed down the caldera wall. A total of ∼ 51−59 km 3 of magma was ejected in the precursory and climactic eruptions, and ∼ 40−52 km 3 of Mount Mazama was lost by caldera formation. The spectacular compositional zonation shown by the climactic ejecta — rhyodacite followed by subordinate andesite and mafic andesite — reflects partial emptying of a zoned system, halted when the crystal-rich magma became too viscous for explosive fragmentation. This zonation was probably brought about by convective separation of low-density, evolved magma from underlying mafic magma. Confinement of postclimactic eruptive activity to the caldera attests to continuing existence of the Mazama magmatic system.

Mount Mazama, Crater Lake, Cascade Range↗

USGS2019

Character of community response to volcanic crises at Sinabung and Kelud volcanoes

Volcano disaster mitigation is a priority in Indonesia's national development plan due to the large number of active volcanoes, high frequency of eruptions and dense population within volcanic hazards zones. As a consequence of these factors and the many decades of experience in mitigation of volcanic risk, Indonesia demonstrates that effective community response is critical to avoid disasters. Understanding of hazards, risks and early-warning systems are the main factors in building an effective community response. The level of understanding of these factors is proportional to a community's independence in taking appropriate actions and is reflected in the community's preparedness. Further, the experience gained from responses to the eruptions of Sinabung and Kelud as well as from other Indonesian volcanoes shows that a local leader plays an important role in mobilizing a community. Such a leader utilizes knowledge of local culture (local wisdom) and an understanding of the community's character to encourage community members to participate and empower themselves. Sharing of information and the formulation of a disaster mitigation plan by government and community also results in a shared commitment to increase participation and community empowerment. Indonesia uses four volcano alert levels to activate community mitigation plans. In order of increasing criticality, these are: Normal, Advisory (Waspada), Watch (Siaga) and Warning (Awas). Implementation of policies, strategies and actions are tied to each level. In addition, mandatory actions by certain stakeholders are required at certain alert levels. These mandatory actions increase the effectiveness of disaster mitigation by both government and community. A comparison of the crisis responses of the Sinabung and Kelud communities is carried out here in order to better understand problems, learn lessons and improve the process of Indonesia's community mitigation policies. Local culture, the start time of community involvement (in normal versus crisis time), degree and level of government involvement, roles of local leaders, local perception of hazards, and political intervention are all factors that influence a community's response at the time of eruption. We stress that an understanding of the “ community character ,” which includes a number of cultural, social and knowledge parameters is essential for effective crisis management. The responses of Sinabung and Kelud illustrate both the key role of community in disaster mitigation and the synergy that can result from close coordination and collaboration between government and community.

Journal of Volcanology and Geothermal Research↗

USGS2009

Optical satellite data volcano monitoring: a multi-sensor rapid response system

In this chapter, the use of satellite remote sensing to monitor active geological processes is described. Specifically, threats posed by volcanic eruptions are briefly outlined, and essential monitoring requirements are discussed. As an application example, a collaborative, multi-agency operational volcano monitoring system in the north Pacific is highlighted with a focus on the 2007 eruption of Kliuchevskoi volcano, Russia. The data from this system have been used since 2004 to detect the onset of volcanic activity, support the emergency response to large eruptions, and assess the volcanic products produced following the eruption. The overall utility of such integrative assessments is also summarized. The work described in this chapter was originally funded through two National Aeronautics and Space Administration (NASA) Earth System Science research grants that focused on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. A skilled team of volcanologists, geologists, satellite tasking experts, satellite ground system experts, system engineers and software developers collaborated to accomplish the objectives. The first project, Automation of the ASTER Emergency Data Acquisition Protocol for Scientific Analysis, Disaster Monitoring, and Preparedness , established the original collaborative research and monitoring program between the University of Pittsburgh (UP), the Alaska Volcano Observatory (AVO), the NASA Land Processes Distributed Active Archive Center (LP DAAC) at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, and affiliates on the ASTER Science Team at the Jet Propulsion Laboratory (JPL) as well as associates at the Earth Remote Sensing Data Analysis Center (ERSDAC) in Japan. This grant, completed in 2008, also allowed for detailed volcanic analyses and data validation during three separate summer field campaigns to Kamchatka Russia. The second project, Expansion and synergistic use of the ASTER Urgent Request Protocol (URP) for natural disaster monitoring and scientific analysis , has expanded the project to other volcanoes around the world and is in progress through 2011. The focus on ASTER data is due to the suitability of the sensor for natural disaster monitoring and the availability of data. The instrument has several unique facets that make it especially attractive for volcanic observations (Ramsey and Dehn, 2004). Specifically, ASTER routinely collects data at night, it has the ability to generate digital elevation models using stereo imaging, it can collect data in various gain states to minimize data saturation, it has a cross-track pointing capability for faster targeting, and it collects data up to ±85° latitude for better global coverage. As with any optical imaging-based remote sensing, the viewing conditions can negatively impact the data quality. This impact varies across the optical and thermal infrared wavelengths as well as being a function of the specific atmospheric window within a given wavelength region. Water vapor and cloud formation can obscure surface data in the visible and near infrared (VNIR)/shortwave infrared (SWIR) region due mainly to non-selective scattering of the incident photons. In the longer wavelengths of the thermal infrared (TIR), scattering is less of an issue, but heavy cloud cover can still obscure the ground due to atmospheric absorption. Thin clouds can be optically-transparent in the VNIR and TIR regions, but can cause errors in the extracted surface reflectance or derived surface temperatures. In regions prone to heavy cloud cover, optical remote sensing can be improved through increased temporal resolution. As more images are acquired in a given time period the chances of a clear image improve dramatically. The Advanced Very High Resolution Radiometer (AVHRR) routine monitoring, which commonly collects 4-6 images per day of any north Pacific volcano, takes advantage of this fact. The rapid response program described in this chapter also improves the temporal resolution of the ASTER instrument. ASTER has been acquiring images of volcanic eruptions since soon after its launch in December 1999. An early example included the observations of the large pyroclastic flow deposit emplaced at Bezymianny volcano in Kamchatka, Russia. The first images in March 2000, just weeks after the eruption, revealed the extent, composition, and cooling history of this large deposit and of the active lava dome (Ramsey and Dehn, 2004). The initial results from these early datasets spurred interest in using ASTER data for expanded volcano monitoring in the north Pacific. It also gave rise to the multi-year NASA-funded programs of rapid response scheduling and imaging throughout the Aleutian, Kamchatka and Kurile arcs. Since the formal establishment of the programs, the data have provided detailed descriptions of the eruptions of Augustine, Bezymianny, Kliuchevskoi and Sheveluch volcanoes over the past nine years (Wessels et al., in press; Carter et al., 2007, 2008; Ramsey et al., 2008; Rose and Ramsey, 2009). The initial research focus of this rapid response program was specifically on automating the ASTER sensor’s ability for targeted observational scheduling using the expedited data system. This urgent request protocol is one of the unique characteristics of ASTER. It provides a limited number of emergency observations, typically at a much-improved temporal resolution and quicker turnaround with data processing in the United States rather than in Japan. This can speed the reception of the processed data by several days to a week. The ongoing multi-agency research and operational collaboration has been highly successful. AVO serves as the primary source for status information on volcanic activity, working closely with the National Weather Service (NWS), Federal Aviation Administration (FAA), military and other state and federal emergency services. Collaboration with the Russian Institute of Volcanology and Seismology (IVS)/Kamchatka Volcanic Eruption Response Team (KVERT) is also maintained. Once a volcano is identified as having increased thermal output, ASTER is automatically tasked and the volcano is targeted at the next available opportunity. After the data are acquired, scientists at all the agencies have access to the images, with the primary science analysis carried out at the University of Pittsburgh and AVO. Results are disseminated to the responsible monitoring agencies and the global community through e-mail mailing lists.

Book chapter↗