scholarly journals Influence of Hydrothermal Recharge on the Evolution of Eruption Styles and Hazards During the 2018–2019 Activity at Kuchinoerabujima Volcano, Japan

2021 ◽  
Author(s):  
Yusuke Minami ◽  
Keiko Matsumoto ◽  
Nobuo Geshi ◽  
Hiroshi Shinohara
Keyword(s):  
Hydrothermal Fluid ◽  
Volcanic Ash ◽  
Volcanic Rocks ◽  
Magmatic Activity ◽  
Density Currents ◽  
Eruption Style ◽  
Sulfate Minerals ◽  
Acid Fluid ◽  
Leachate Analysis ◽  
Explosive Phase

Abstract The activity of the 2018-2019 eruption of Kuchinoerabujima Volcano in Japan changed from continuous ejection of ash-laden plumes between October 21 and the middle of December, to intermittent explosive activity accompanied by several pyroclastic density currents until January 2019. To understand the behaviors of magma and hydrothermal fluid that controlled the eruptive sequence, we carried out component analysis, X-ray diffractometry, and leachate analysis for ash samples. The proportion of non-altered volcanic ash particles is ~15 % in the earlier phase, then it decreased to less than 10 % in the later explosive phase. Accordingly, the mineral assemblage of the volcanic ash samples changed from plagioclase-dominant to sulfate minerals-dominant. Concentration of SO42- and Cl/SO4 values of the ash-leachates decreased toward the later activity. These results indicate that the proportion of fresh volcanic rocks decreased and sulfuric acid fluid-derived sulfate minerals increased toward the later activities. Consequently, the 2018-2019 eruption at Kuchinoerabujima Volcano changed from magmatic activity to phreatomagmatic activity. Weak glowing of the crater was observed during the magmatic activity, indicating the volcanic conduit was hot enough to dry up the subvolcanic hydrothermal system. The following phreatomagmatic activity indicates that the hydrothermal fluid recharged after the magmatic eruption phase. Recharge of the hydrothermal fluid likely caused the variation of the eruption style, and is a process that may control the evolution of hazards during future eruption scenarios at similar active volcanoes in Japan and worldwide.

Automatic onsite imaging of volcanic ash particles with VOLCAT: Towards quasi-real-time eruption style monitoring

2021 ◽  
pp. 107267
Author(s):  
Takahiro Miwa ◽  
Nobuo Geshi ◽  
Jun'ichi Itoh ◽  
Toshikazu Tanada ◽  
Masato Iguchi
Keyword(s):  
Real Time ◽  
Volcanic Ash ◽  
Eruption Style

scholarly journals Experimental constraints on volcanic ash generation and clast morphometrics in pyroclastic density currents and granular flows

Volcanica ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 263-283
Author(s):  
Adrian Hornby ◽  
Ulrich Kueppers ◽  
Benedikt Mauer ◽  
Carina Poetsch ◽  
Donald Dingwell
Keyword(s):  
Volcanic Ash ◽  
Direct Evidence ◽  
General Description ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Generation Efficiency ◽  
Bed Height ◽  
Ash Removal ◽  
Shape Changes ◽  
Basal Flow

Pyroclastic density currents (PDCs) are a prominent hazard of volcanic activity; however, fully quantitative observations are lacking and little direct evidence exists to constrain the parameters controlling ash production and runout. Here, we use rotary tumbling experiments to investigate ash generation efficiency and clast morphometrics in the dense basal flow of PDCs. We observe greater ash generation with periodic ash removal and with higher starting mass. By scaling to the bed height and clast diameter we obtain a general description for ash production in all experiments as a function of flow distance that we parameterise in dimensionless space. We also show that ash production correlates with clast shape changes and with the Inertial number for our experiments. This work introduces some of the first systematic and generalizable experimental parameterizations of ash production and clast evolution in PDCs and should advance the ability to understand flow mobility and associated hazards.

scholarly journals Detailed mapping and lithogeochemistry of Neoarchean volcanic rocks: Beaulieu volcanic belt, Slave Craton, NWT

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Shelby Brandon Austin-Fafard ◽  
Michelle DeWolfe ◽  
Camille Partin ◽  
Bernadette Knox
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Massive Sulfide ◽  
Lake Area ◽  
Density Currents ◽  
Volcanogenic Massive Sulfide ◽  
The South ◽  
Slave Craton ◽  
Volcaniclastic Rocks ◽  
Tuff Breccia

Neoarchean volcanic rocks of the Beaulieu River volcanic belt structurally overlie basement rocks of the Sleepy Dragon Complex (ca. 2.85 Ga), approximately 100 km east northeast of Yellowknife. The volcanic belt is comprised of complex lithofacies, including basalt, andesite, rhyolite, and associated volcaniclastic rocks, and hosts the Sunrise volcanogenic massive sulfide deposit. The absolute age of the volcanic strata is not known, nor is the stratigraphy well-defined; therefore, the Beaulieu River volcanic belt cannot be easily correlated to other greenstone belts within the Slave craton. The main objective of this study is to document the litho- and chemo-stratigraphy of the volcanic rocks, and particularly the rhyolite dome, located at the south end  of Sunset Lake to reconstruct their volcanic and petrogenetic evolution, and determine their relationship to the volcanic strata that hosts the Sunrise VMS deposit, located ~6km to the north of the study area. Detailed mapping (1:2000) was completed over two field seasons (2018 and 2019) and shows that the volcanic rocks in the south Sunset Lake area comprise a complex stratigraphy consisting of basaltic, andesitic and rhyolitic lithofacies. This includes massive to pillow basalt and andesite, with lesser amounts of massive to in-situ brecciated, weakly quartz-plagioclase porphyritic rhyolite, heterolithic tuff to lapilli- tuff and felsic tuff to tuff breccia. The felsic clasts within the felsic volcaniclastic rocks are similar in composition to the coherent rhyolite. Units have a trace element geochemical signatures that vary from tholeiitic to calc-alkaline, arc-like rocks. Volumetrically, the volcanic strata in the south Sunset Lake area has a significant amount of volcaniclastic rocks, ranging from tuff to tuff breccia units. The volcaniclastic rocks are interpreted to have been deposited by a series of debris flows and eruption-fed density currents. The stratigraphy of the volcanic rocks in south Sunset Lake is very similar to that of the stratigraphy that hosts the Sunrise VMS deposit. Evidence of a vent proximal environment (e.g. rhyolite dome, peperite, syn-volcanic intrusions) and porous, volcanic debris accumulating on the seafloor highlight conditions favourable for volcanogenic massive sulfide-type mineralization in the south Sunset Lake area.

scholarly journals Late Ordovician volcanism of the northern part of Altai-Sayan area and its geodynamic nature

2019 ◽  
Vol 485 (4) ◽  
pp. 457-463
Author(s):  
A. A. Vorontsov ◽  
O. Yu. Perfilova ◽  
N. N. Kruk ◽  
A. S. Tarasyuk
Keyword(s):  
Mantle Plume ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Late Ordovician ◽  
Magmatic Activity ◽  
Geological Data ◽  
Tio2 Content ◽  
Evolution Stage ◽  
Geochemical Studies ◽  
Ree Pattern

The results of geological-geochemical studies of some Late Ordovician associations in the frame of the Minusinsk Trough with available geological and U-Pb, Rb-Sr, and K-Ar age dates are presented. The Late Ordovician volcanic rocks form a continuous igneous series, the basalts of which are different from Devonian basalts of the Minusinsk Trough in the lower TiO2 content (≥1.7 wt %) and more fractionated REE pattern. These features should be considered the index characteristics of Late Ordovician rocks. Their compositions reflect processes of fractionation crystallization and mixing of trachibasaltic magmas with crustal melts. When taking into account the regional geological data, it is shown that magmatic activity at the Late Ordovician endogenic evolution stage in the northern part of the Altai-Sayan fold area was caused by the interaction of a mantle plume and the lithospheric mantle, which was metasomatically reworked and enriched in water during former subduction processes.

Volcano-stratigraphy of the extension-related silicic volcanism of the Çubukludağ Graben, western Turkey: an example of generation of pyroclastic density currents

2013 ◽  
Vol 151 (3) ◽  
pp. 492-516 ◽  
Author(s):  
ZEKIYE KARACIK ◽  
SENGUL C. GENÇ
Keyword(s):  
Volcanic Rocks ◽  
Central Anatolia ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Western Turkey ◽  
Silicic Volcanism ◽  
Fine Grained ◽  
Sediment Deformation ◽  
Volcanic Succession ◽  
Lake Waters

AbstractWestern Turkey's extension-related Cumaovası volcanic rocks (Lower Miocene, 17 Ma) are excellent examples of silicic eruptions. The sub-aerial silicic volcanism at Çubukludağ Graben between İzmir and Kuşadası in west–central Anatolia is mainly in the form of rhyolite domes, lava flows and pyroclastic deposits. The initial features of volcanism derived from phreatomagmatic explosive eruptions from silicic magma that came into contact with lake waters during Neogene times. Most of the volcanic succession represents pyroclastic density currents (PDCs), known as the Kuner ignimbrite. The deposits are fine grained and laminated at the base and pass laterally and vertically into deposits displaying well-developed traction structures, soft sediment deformation and/or erosion channels in the NE part of the region. Alternate deposits of massive, diffusely stratified lapilli and ash are the main products of the later explosive stage. Massive lithic breccias forming the top of the sequences are the proximal facies of the PDCs. The lava phase mainly consists of rhyolite extruded as dome and fissure eruptions of lavas, aligned along NE–SW-trending faults as well as from extensional cracks that are nearly perpendicular to the main graben faults. Considering the tectono-stratigraphical aspects and geochemical nature of the study area, we propose that the Cumaovası silicic volcanism was produced by extension-related crustal melting during the Late–Early Miocene period (17 Ma).

scholarly journals Sulphur dioxide as a volcanic ash proxy during the April–May 2010 eruption of Eyjafjallajökull Volcano, Iceland

2011 ◽  
Vol 11 (14) ◽  
pp. 6871-6880 ◽  
Author(s):  
H. E. Thomas ◽  
A. J. Prata
Keyword(s):  
Western Europe ◽  
Volcanic Ash ◽  
Final Phase ◽  
Middle Phase ◽  
Eruption Style ◽  
Infrared Imager ◽  
Cloud Monitoring ◽  
Volcanic Ash Cloud ◽  
Volcanic Cloud ◽  
Financial Losses

Abstract. The volcanic ash cloud from the eruption of Eyjafjallajökull volcano in April and May 2010 resulted in unprecedented disruption to air traffic in Western Europe causing significant financial losses and highlighting the importance of efficient volcanic cloud monitoring. The feasibility of using SO2 as a tracer for the ash released during the eruption is investigated here through comparison of ash retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) with SO2 measurements from a number of infrared and ultraviolet satellite-based sensors. Results demonstrate that the eruption can be divided into an initial ash-rich phase, a lower intensity middle phase and a final phase where considerably greater quantities both ash and SO2 were released. Comparisons of ash-SO2 dispersion indicate that despite frequent collocation of the two species, there are a number of instances throughout the eruption where separation is observed. This separation occurs vertically due to the more rapid settling rate of ash compared to SO2, horizontally through wind shear and temporally through volcanological controls on eruption style. The potential for the two species to be dispersed independently has consequences in terms of aircraft hazard mitigation and highlights the importance of monitoring both species concurrently.

scholarly journals Atmospheric processes affecting the separation of volcanic ash and SO<sub>2</sub> in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

2017 ◽  
Vol 17 (17) ◽  
pp. 10709-10732 ◽  
Author(s):  
Fred Prata ◽  
Mark Woodhouse ◽  
Herbert E. Huppert ◽  
Andrew Prata ◽  
Thor Thordarson ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Early Stage ◽  
Volcanic Eruptions ◽  
Radiation Balance ◽  
Eruption Column ◽  
Density Currents ◽  
Volcanic Emissions ◽  
Main Column ◽  
The Masses ◽  
High Level

Abstract. The separation of volcanic ash and sulfur dioxide (SO2) gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21–28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources coupled with meteorological wind data and photographic evidence suggest that the eruption column was unable to sustain itself, resulting in a large deposition of ash, which left a low-level ash-rich atmospheric plume moving southwards and then eastwards towards the southern Scandinavian coast and a high-level predominantly SO2 plume travelling northwards and then spreading eastwards and westwards. Here we provide observational and modelling perspectives on the separation of ash and SO2 and present quantitative estimates of the masses of ash and SO2 that erupted, the directions of transport, and the likely impacts. We hypothesise that a partial column collapse or sloughing fed with ash from pyroclastic density currents (PDCs) occurred during the early stage of the eruption, leading to an ash-laden gravity intrusion that was swept southwards, separated from the main column. Our model suggests that water-mediated aggregation caused enhanced ash removal because of the plentiful supply of source water from melted glacial ice and from entrained atmospheric water. The analysis also suggests that ash and SO2 should be treated with separate source terms, leading to improvements in forecasting the movement of both types of emissions.

scholarly journals Rapid eruptive transitions from low to high intensity explosions and effusive activity: insights from textural analysis of a small-volume trachytic eruption, Ascension Island, South Atlantic

2021 ◽  
Vol 83 (9) ◽  
Author(s):  
Bridie V. Davies ◽  
Richard J. Brown ◽  
Jenni Barclay ◽  
Jane H. Scarrow ◽  
Richard A. Herd
Keyword(s):  
High Intensity ◽  
Small Volume ◽  
Early Stage ◽  
Eruption Dynamics ◽  
Eruption Style ◽  
Effusive Activity ◽  
Ascension Island ◽  
Explosive Phase ◽  
The Impact ◽  
Textural Evidence

AbstractProximal deposits of small-volume trachytic eruptions are an under-studied record of eruption dynamics despite being common across a range of settings. The 59 ± 4 ka Echo Canyon deposits, Ascension Island, resulted from a small-volume explosive-effusive trachytic eruption. Variations in juvenile clast texture reveal changes in ascent dynamics and transitions in eruption style. Five dominant textural types are identified within the pumice lapilli population. Early Strombolian-Vulcanian eruption phases are typified by macro- and micro-vesicular equant clast types. Sheared clasts are most abundant at the eruption peak, transitioning to dense clasts in later phases due to shear-induced coalescence, outgassing and vesicle collapse. Melt densification and outgassing via tuffisite veins increased plume density, contributing to partial column collapse and the explosive-effusive transition. Bulk vesicularity distributions indicate a shift in dominant fragmentation mechanism during the eruption, from early-stage bubble interference and rupture to late-stage transient fragmentation, with a transient peak of Plinian activity. Dome and lava groundmass crystallinities of up to 70% indicate near-complete degassing during effusive phases, followed by shallow over pressurisation and a final less explosive phase. We provide textural evidence for high-intensity explosive phases and rapid transitions in eruptive style during small-volume trachytic eruptions and consider the impact of trachytic melt compositions on underlying dynamics of these short-lived, explosive events. This analysis demonstrates the value of detailed stratigraphy in understanding critical changes in eruption dynamics and the timescales over which they may occur which is of particular value in anticipating future eruptions of this type.

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