Journal articles on the topic 'Submarine explosive volcanism'
To see the other types of publications on this topic, follow the link: Submarine explosive volcanism.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 45 journal articles for your research on the topic 'Submarine explosive volcanism.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Maksimov, S. O. "TIME PULSES OF CENOZOIC EXPLOSIVE PHREATIC ERUPTIONS IN SOUTHWESTERN PRIMORYE. CORRELATION OF ISOTOPIC AND PHYTOSTRATIGRAPHIC AGE DATING RESULTS." Tikhookeanskaya Geologiya 41 (2022): 50–75. http://dx.doi.org/10.30911/0207-4028-2022-41-3-50-75.
Full textAbstract:
The Cenozoic tephra deposits - products of explosive phreatic eruptions of maar volcanoes in the southwest of Primorye are studied. The deposits represent rhyolitic ash and pumice pyroclastic beds with a high terrigenous component, including tephroid pseudo-conglomerates. Isotopic dating of tephra beds established two time pulses of explosive volcanism: 30–34 Mya and 23–24 Mya. The first time pulse coincided with the beginning of the formation of marginal seas and continental coal basins. It corresponds to the most productive stage of coal accumulation, the burial of wood wastes and their coalification at a faster rate, and the development of a high-temperature geothermal field and can be compared with the well-known catastrophic eruption of Mount St. Helens in the U.S.A. The second time pulse of explosive volcanism had a regional character of manifestation. It is characterized by the formation of green tuff complexes on submarine elevations of the Sea of Japan as well as along the western and eastern coasts of Japan. Synchronously with the volcanic activity started the acceleration of the sinking rate of the Sea of Japan bottom in response to the active rising of asthenospheric diapirs. The established isotopic ages do not conform to the ages determined for fossil leaves and pollen from the deposits, which may reflect the climate-forming type of such an explosive process.
2
Weiß, B. J., C. Hübscher, D. Wolf, and T. Lüdmann. "Submarine explosive volcanism in the southeastern Terceira Rift/São Miguel region (Azores)." Journal of Volcanology and Geothermal Research 303 (September 2015): 79–91. http://dx.doi.org/10.1016/j.jvolgeores.2015.07.028.
Full text
3
Sayyadi, Sara, Magnús Tumi Gudmundsson, and Páll Einarsson. "Volcanic tremor associated with the Surtsey eruption of 1963–1967." Jokull 72, no. 1 (2022): 21–34. http://dx.doi.org/10.33799/jokull2022.72.021.
Full textAbstract:
The formation of the island of Surtsey over 3.5 years, remains one of the best-documented volcanic, island-forming eruptions to date. The basaltic submarine volcanic activity was detected on November 14, 1963, where ocean depth was 130 m prior to the eruption at the southern end of the Vestmannaeyjar archipelago. The eruptions occurred in several phases involving explosive and effusive activity, including the initial submarine phase on November 12–13, 1963. Separate phases of subaerial volcanic activity occurred during November 14, 1963–January 1964, January–April 1964, April 1964–May 1965, May–October 1965, December 1965–August 1966, and August 1966–June 1967. Seismic data quality from this period is inferior compared to that of modern monitoring systems. Four permanent seismic stations were operated in Iceland at the time, whereof only two, located at 115 and 140 km distance, had the sensitivity to record tremor from Surtsey. Nevertheless, the scanned analog seismograms (http://seismis.hi.is/) show that the eruptive activity was accompanied by considerable seismic activity, both earthquakes, and volcanic tremor. Earthquakes were primarily associated with changes in vent location. Both spasmodic and harmonic tremor was identified, both with low (<3 Hz) and higher (3–5 Hz) characteristic frequencies. The results indicate a complicated relationship between tremor and magma flow rate or style of activity. During the explosive eruption, the highest magma flow rates occurred in the first 10–20 days, a period with little observed tremor. The highest tremor is observed in December 1963–March 1964, after the discharge rates had dropped substantially, and on a timescale of hours-to-days, no clear relationship between tremor and eruption style is observed. The same applies to the effusive activity, where no seismic tremor was observed during most of the effusive eruption of Surtungur, despite the fact that magma flow rates were ~3 times higher than during later phases where some tremor was observed. Keywords: Submarine volcanism, eruption precursors, volcanic tremor, precursory tremor, continuous uprush eruptions
4
Inza, Coulibaly, Kouamelan Alain Nicaise, Djro Sagbrou Chérubin, and Coulibaly Yacouba. "Petrographie Des Volcanites Et Plutonites De La Partie Sud Du Sillon Volcano-Sedimentaire De Toumodi-Fetekro (Cote D’ivoire)." European Scientific Journal, ESJ 13, no. 30 (October 31, 2017): 199. http://dx.doi.org/10.19044/esj.2017.v13n30p199.
Full textAbstract:
The southern part of Toumodi-Fètêkro greenstone belt is located in the Center - Southeast of Ivory Coast. Petrographic study of volcanic and plutonic rocks shows three units. The first unit is composed of basaltic to rhyolitic lavas which imply effusive character. Then we have volcanosedimentary unit composed of pyroclastic formations (lapilli tuff, breccia, ash deposit and ignimbrites) and the pillow-lavas. Indeed, the presence of this last shows clearly that an explosive volcanism and a submarine effusive volcanism have occurred during during the setting of Toumodi-Fètêkro belt. Plutonic unit is constituted of gabbroic to granitic rocks. Sericite, chlorite, epidote observed in these rocks are consistent with the impacts of greenschist facies metamorphism. The rocks of the southern part of the Toumodi-Fètêkro greenstone belt are formed in a subduction context rather than in oceanic plateaus context because of the old inheritance, sometimes of Archean age, found somewhere in theBirimiandomain. The lithologies of the southern part of Toumodi-Fètêkro meet elsewhere in the other Birimian greenstone belts. Also, these lithologies are affected by a hydrothermal alteration due to the abundant veins of quartz, carbonates, sericite, chlorite, epidote, sulphides and oxides. However, volcanic show in some places amphibolit facies metamorphism.
5
Verolino, Andrea, James D. L. White, Rachael J. M. Baxter, C. Ian Schipper, and Thor Thordarson. "Characteristics of Sub-Aerially Emplaced Pyroclasts in the Surtsey Eruption Deposits: Implications for Diverse Surtseyan Eruptive Styles." Geosciences 12, no. 2 (February 8, 2022): 79. http://dx.doi.org/10.3390/geosciences12020079.
Full textAbstract:
The 1963–1967 shallow-to-emergent eruption in Iceland’s Vestmannaeyjar earned a place in the history of volcanology by creating the island of Surtsey while under close observation of volcanologist Sigurdur Thorarinsson (Sigurður Þórarinsson in Icelandic). This is an example of what is now called Surtseyan volcanism, and it included explosive and effusive phases from multiple vents that formed the island of Surtsey itself, as well as one fully subaqueous pyroclastic edifice and two additional, but ephemeral, islands. Sigurdur Thorarinsson identified tephra jetting and continuous uprush as characteristic types of subaerial explosive activity of Surtseyan volcanism. Subaerial cone-forming deposits of Surtseyan volcanism are typically poorly sorted, with fine-grained beds rich in sideromelane ash fragments, punctuated by larger, ubiquitously composite bombs, whereas deposits sampled by coring deep into the submarine edifice include fines-poor horizons dominated by vesicular coarse sideromelane ash. Here, we present new textural data and highlight the diversity of pyroclasts and microtextures from Surtsey (Surtur I and Surtur II) and its satellite vents (Surtla, Syrtlingur and Jolnir), in the context of Surtseyan volcanism. We used several sample sets. Some were collected during the 3.5-year long eruption and were conserved in the Icelandic Natural History Museum, including one sample from the core drilled into Surtsey in 1979. Other samples were collected during more recent field campaigns on Surtsey Island. In closing, we discuss the implications of this diversity for the range of activity and products produced by Surtsey.
6
Doucet, P., W. Mueller, and F. Chartrand. "Archean, deep-marine, volcanic eruptive products associated with the Coniagas massive sulfide deposit, Quebec, Canada." Canadian Journal of Earth Sciences 31, no. 10 (October 1, 1994): 1569–84. http://dx.doi.org/10.1139/e94-139.
Full textAbstract:
The mafic-dominated volcanic and related volcaniclastic sedimentary rocks, which host the Archean Coniagas Zn–Pb–Ag massive sulfide deposit, are inferred to be the result of submarine explosive and effusive eruptions at depths of approximately 1000 m, as suggested by the presence of volcaniclastic turbidites, the absence of wave-induced sedimentary structures, pillowed lava flows, the sulfide deposit itself, and the incipient arc setting. The rock assemblage includes massive, pillowed and brecciated, basaltic to andesitic flows, massive, andesitic to rhyodacitic lapilli tuffs, andesitic stratified lapilli tuffs, and bedded tuffs. Preserved fragments and delicate volcanic textures, such as angularity of clasts, chilled clast margins, and clast vesicularity, and sedimentary structures are consistent with a subaqueous hydroclastic origin for the volcaniclastic sedimentary rocks. Explosive degasification of magma and (or) lava, in conjunction with fragmentation due to the interaction of magma–water, or nonexplosive hydroclastic fragmentation can account for the observed characteristics in the volcaniclastic deposits.The 280 m thick Coniagas volcano-sedimentary succession, used to reconstruct the volcanic history of the deposit, records two explosive–effusive volcanic cycles. The initial stage of each cycle is envisaged to have commenced with a small fire fountain or boiling-over eruption. Transport and deposition of the fragmented debris along the flanks of the volcanic edifice is attributed to high-concentration particulate gravity flows. The massive lapilli tuffs are interpreted as laminar debris flows, whereas the stratified lapilli tuffs may reflect turbulent flow deposits. The bedded tuffs were produced during the waning eruptive stages or elutriated from high-concentration syneruption flows. Ingestion of water, causing hydroclastic fragmentation, occurred during the eruptive and (or) the transport process. Calm, effusive mafic volcanism, characterized by massive, pillowed and brecciated flows and reworked counterparts, terminates each volcanic cycle. The massive, felsic lapilli tuffs, which host the mineralization, are inferred to represent locally reworked hydroclastic products of explosive or nonexplosive origin. The Coniagas mine deposit may serve as a guide for future exploration of small Archean volcanic-hosted massive sulfide deposits with a restricted alteration halo.
7
Farmer, Jack D., Maria C. Farmer, and Rainer Berger. "Radiocarbon Ages of Lacustrine Deposits in Volcanic Sequences of the Lomas Coloradas Area, Socorro Island, Mexico." Radiocarbon 35, no. 2 (1993): 253–62. http://dx.doi.org/10.1017/s0033822200064924.
Full textAbstract:
Extensive eruptions of alkalic basalt from low-elevation fissures and vents on the southern flank of the dormant volcano, Cerro Evermann, accompanied the most recent phase of volcanic activity on Socorro Island, and created the Lomas Coloradas, a broad, gently sloping terrain comprising the southern part of the island. We obtained 14C ages of 4690 ± 270 BP (5000–5700 cal BP) and 5040 ± 460 BP (5300–6300 cal BP) from lacustrine deposits that occur within volcanic sequences of the lower Lomas Coloradas. Apparently, the sediments accumulated within a topographic depression between two scoria cones shortly after they formed. The lacustrine environment was destroyed when the cones were breached by headward erosion of adjacent stream drainages. This was followed by the eruption of a thin basaltic flow from fissures near the base of the northernmost cone. The flow moved downslope for a short distance and into the drainages that presently bound the study area on the east and west. The flow postdates development of the present drainage system and may be very recent. Our 14C data, along with historical accounts of volcanic activity over the last century, including submarine eruptions that occurred a few km west of Socorro in early 1993, underscore the high risk for explosive volcanism in this region and the need for a detailed volcanic hazards plan and seismic monitoring.
8
Rubingh, Kate E., Harold L. Gibson, and Bruno Lafrance. "Evidence for voluminous bimodal pyroclastic volcanism during rifting of a Paleoproterozoic arc at Snow Lake, Manitoba." Canadian Journal of Earth Sciences 54, no. 6 (June 2017): 654–76. http://dx.doi.org/10.1139/cjes-2016-0163.
Full textAbstract:
The thrust-bounded McLeod Road – Birch Lake (MB) sequence occurs within the Paleoproterozoic Snow Lake arc (SLA) assemblage of the Flin Flon belt. Stratigraphic correlation of volcanic strata of the MB sequence with strata of the thrust-bounded Chisel sequence indicates that distinctive, submarine, eruption-fed, pyroclastic flow deposits are more extensive and voluminous than previously recognized (>10 km3). These voluminous felsic pyroclastic deposits define a distinct magmatic and explosive volcanic event during bimodal volcanism that accompanied rifting of the SLA. The felsic pyroclastic deposits define the remnants of a basin, or of nested basins, that formed during arc rifting and subsidence, and their eruption immediately preceded formation of the Chisel sequence volcanogenic massive sulfide (VMS) deposits. Although the Chisel sequence ore interval is recognized in the MB sequence, the lack of VMS-related alteration indicates that VMS hydrothermal activity was restricted to the Chisel portion of the basin. However, the MB sequence is host to the younger Snow Lake gold mine, a 1.4M oz (43 699 kg) gold producer. The overlying MORB-like Birch Lake basalts, if conformable with the MB sequence, may represent a progression from a rifted-arc to a back-arc setting. However, if they are thrust fault bounded, then they may represent the initial phases of arc-rifting, prior to the voluminous felsic pyroclastic eruptions. Correlation and integrity of stratigraphy between the thrust-bounded MB and SLA sequences indicates that the bounding thrust faults, which developed during accretionary processes, have less regional significance than previously interpreted.
9
Vermeij, Geerat J. "Economics, volcanoes, and Phanerozoic revolutions." Paleobiology 21, no. 2 (1995): 125–52. http://dx.doi.org/10.1017/s0094837300013178.
Full textAbstract:
Two intervals of the Phanerozoic stand out as times of biosphere-scale revolution in the sense that biogeochemical cycles came under increased control by organisms. These are the early Paleozoic (extending from just before the Cambrian to the Middle Ordovician, a duration of about 100 m.y.), characterized by the appearance of predators, burrowers, and mineralized skeletons, and by the subsequent diversification of planktonic animals and suspension-feeders; and the later Mesozoic (latest Triassic to mid-Cretaceous, a duration of somewhat more than 100 m.y.), marked by a great diversification of predators and burrowers and by the rise of mineralized planktonic protists. This paper explores the economic conditions that make such revolutions possible.I argue that opportunities for innovation and diversification are enhanced when raw materials and energy are supplied at increasing rates, or when organisms gain greater access to these commodities through rising temperatures and higher metabolic rates. Greater per capita availability of resources enables populations to grow; lessens or alters ecological constraints on functional improvement; makes possible the evolution of high metabolic rates (large incomes), which in turn permit improvement in each of several otherwise incompatible functions; and favors the establishment and spread of daughter species arising through founder speciation. Reductions in productivity reinforce adaptational constraints and may bring about extinctions.Massive submarine volcanism, together with its associated phenomena of warming, sea-level rise, and widening of warm-weather zones, is proposed to be the chief extrinsic trigger for the Phanerozoic revolutions. The later Mesozoic was characterized by continental rifting, which accompanied massive submarine volcanic eruptions that produced large quantities of nutrients and carbon dioxide. This activity began in the Late Triassic and peaked in the mid- to Late Cretaceous. The Early Cambrian was also a time of rifting and may likewise have been marked by large-scale submarine volcanism. Continental and explosive volcanism, weathering, and upwelling are other potential means for increasing evolutionary opportunity, but their effects are either local or linked directly or indirectly with cooling. Intense chemical weathering in the Early Cambrian, however, may have contributed to the early Paleozoic revolution.The extrinsic stimulus was greatly amplified through positive feedback by the evolution of higher metabolic rates and other means for acquiring, trading, retaining, and recycling resources more rapidly and from a wider range of environments. Because these novelties usually require a high and predictable supply of resources, their evolution is more likely when extrinsically controlled supplies increase rather than when per capita availability is low.In the view adopted here, the microevolutionary and microeconomic market forces of competition and natural selection operate against a backdrop of macroeconomic supply and demand. Resources are under both extrinsic and intrinsic control. Positive and negative feedbacks link processes at the micro- and macroeconomic levels. This view complements the genealogical and hierarchical conception of evolution by emphasizing that the pattern of descent is influenced by resources and by market forces operating at all scales of space and time.
10
Sun, Qiliang, Christopher A. L. Jackson, Craig Magee, Samuel J. Mitchell, and Xinong Xie. "Extrusion dynamics of deepwater volcanoes revealed by 3-D seismic data." Solid Earth 10, no. 4 (August 2, 2019): 1269–82. http://dx.doi.org/10.5194/se-10-1269-2019.
Full textAbstract:
Abstract. Submarine volcanism accounts for ca. 75 % of the Earth's volcanic activity. Yet difficulties with imaging their exteriors and interiors mean that the extrusion dynamics and erupted volumes of deepwater volcanoes remain poorly understood. Here, we use high-resolution 3-D seismic reflection data to examine the external and internal geometry and extrusion dynamics of two late Miocene–Quaternary deepwater (> 2 km emplacement depth) volcanoes buried beneath 55–330 m of sedimentary strata in the South China Sea. The volcanoes have crater-like bases, which truncate underlying strata and suggest extrusion was initially explosive, and erupted lava flows that feed lobate lava fans. The lava flows are > 9 km long and contain lava tubes that have rugged basal contacts defined by ∼90±23 m high erosional ramps. We suggest the lava flows eroded down into and were emplaced within wet, unconsolidated, near-seafloor sediments. Extrusion dynamics were likely controlled by low magma viscosities as a result of increased dissolved H2O due to high hydrostatic pressure and soft, near-seabed sediments, which are collectively characteristic of deepwater environments. We calculate that long-runout lava flows account for 50 %–97 % of the total erupted volume, with a surprisingly minor component (∼3 %–50 %) being preserved in the main volcanic edifice. Accurate estimates of erupted volumes therefore require knowledge of volcano and lava basal surface morphology. We conclude that 3-D seismic reflection data are a powerful tool for constraining the geometry, volumes, and extrusion dynamics of ancient or active deepwater volcanoes and lava flows.
11
Kutterolf, Steffen, Julie C. Schindlbeck, Rachel P. Scudder, Richard W. Murray, Kevin T. Pickering, Armin Freundt, Shasa Labanieh, et al. "Large volume submarine ignimbrites in the Shikoku Basin: An example for explosive volcanism in the Western Pacific during the Late Miocene." Geochemistry, Geophysics, Geosystems 15, no. 5 (May 2014): 1837–51. http://dx.doi.org/10.1002/2014gc005263.
Full text
12
Sager, W. W., T. Sano, and J. Geldmacher. "IODP Expedition 324: Ocean Drilling at Shatsky Rise Gives Clues about Oceanic Plateau Formation." Scientific Drilling 12 (September 1, 2011): 24–31. http://dx.doi.org/10.5194/sd-12-24-2011.
Full textAbstract:
Integrated Ocean Drilling Program (IODP) Expedition 324 cored Shatsky Rise at five sites (U1346–U1350) to study processes of oceanic plateau formation and evolution. Site penetrations ranged from 191.8 m to 324.1 m with coring of 52.6 m to 172.7 m into igneous basement at four of the sites. Average recovery in basement was 38.7%–67.4%. Cored igneous sections consist mainly of variably evolved tholeiitic basalts emplaced as pillows or massive flows. Massive flows are thickest and make up the largest percentage of section on the largest and oldest volcano, late Jurassic age Tamu Massif; thus, it may have formed at high effusion rates. Such massive flows are characteristic of flood basalts, and similar flows were cored at Ontong Java Plateau. Indeed, the similarity of igneous sections at Site U1347 with that cored on Ontong Java Plateau implies similar volcanic styles for these two plateaus. On younger, smaller Shatsky Rise volcanoes, pillow flows are common and massive flows thinner and fewer, which might mean volcanism waned with time. Cored sediments from summit sites contain fossils and structures implying shallow water depths or emergence at the time of eruption and normal subsidence since. Summit sites also show pervasive alteration that could be due to high fluid fluxes. A thick section of volcaniclastics cored on Tamu Massif suggests that shallow, explosive submarine volcanism played a significant role in the geologic development of the plateau summit. Expedition 324 results imply that Shatsky Rise began with massive eruptions forming a huge volcano and that subsequent eruptions waned in intensity, forming volcanoes that are large, but which did not erupt with unusually high effusion rates. Similarities of cored sections on Tamu Massif with those of Ontong Java Plateau indicate that these oceanic plateaus formed in similar fashion. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.12.03.2011" target="_blank">10.2204/iodp.sd.12.03.2011</a>
13
Iezzi, Gianluca, Carlo Caso, Guido Ventura, Mattia Vallefuoco, Andrea Cavallo, Harald Behrens, Silvio Mollo, Diego Paltrinieri, Patrizio Signanini, and Francesco Vetere. "First documented deep submarine explosive eruptions at the Marsili Seamount (Tyrrhenian Sea, Italy): A case of historical volcanism in the Mediterranean Sea." Gondwana Research 25, no. 2 (March 2014): 764–74. http://dx.doi.org/10.1016/j.gr.2013.11.001.
Full text
14
Nomikou, Paraskevi, Christian Hübscher, and Steven Carey. "The Christiana–Santorini–Kolumbo Volcanic Field." Elements 15, no. 3 (June 1, 2019): 171–76. http://dx.doi.org/10.2138/gselements.15.3.171.
Full textAbstract:
The Christiana–Santorini–Kolumbo volcanic field in the South Aegean Sea (Greece) is one of the most important in Europe, having produced more than 100 explosive eruptions in the last 400,000 years. Its volcanic centers include the extinct Christiana Volcano and associated seamounts, Santorini caldera with its intracaldera Kameni Volcano, Kolumbo Volcano, and 24 other submarine cones of the Kolumbo chain. Earthquakes, volcanic eruptions, submarine mass wasting, neotectonics and gas releases from these centers pose significant geohazards to human populations and infrastructures of the Eastern Mediterranean region. Defining the geological processes and structures that contribute to these geohazards will provide an important framework to guide future monitoring and research activities aimed at hazard mitigation.
15
Ross, Pierre-Simon, Jean Goutier, Patrick Mercier-Langevin, and Benoît Dubé. "Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 1. Mode of emplacement in three areas1This article is a companion paper to Ross et al. 2011. Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology. Canadian Journal of Earth Sciences, 48: this issue.2MRNF Contribution BEGQ 8439-2010/2011-1. Natural Resources Canada, Earth Science Sector Contribution 20100253." Canadian Journal of Earth Sciences 48, no. 4 (April 2011): 728–56. http://dx.doi.org/10.1139/e10-090.
Full textAbstract:
The Archean Blake River Group (BRG) of Ontario and Quebec is dominated by submarine mafic to intermediate lavas, with more restricted felsic volcanic rocks. Given the good quality of outcrop, and high level of preservation of some BRG rocks, the mafic to intermediate lavas were used in the 1970s and 1980s to better understand the evolution of massive and pillowed submarine flows, and their associated fragmental facies (pillow breccias, hyaloclastite). Potentially, the BRG could also represent a useful volcanic succession for the study of explosive submarine eruption products in the ancient record. Before this is possible, however, a regional inventory of the mafic to intermediate volcaniclastic units is needed to clarify their characteristics and origins. In this paper, we compare and contrast volcaniclastic rocks from three areas within the same formation of the northern BRG in Quebec: the Monsabrais area, the Lac Duparquet area, and the D’Alembert tuff area. Close examination reveals pronounced differences in terms of lateral continuity, thickness, grading, bedding, clast shapes, textures, etc. in the volcaniclastic rocks. These differences are interpreted to reflect vastly different emplacement processes, ranging from hyaloclastite generation as a result of self-fragmentation and lava contact with water (dominant in the Monsabrais and Lac Duparquet areas) to aqueous density currents likely fed directly by explosive submarine eruptions (dominant in the D’Alembert tuff).
16
Romano, Davide, Alessandro Gattuso, Manfredi Longo, Cinzia Caruso, Gianluca Lazzaro, Andrea Corbo, and Francesco Italiano. "Hazard Scenarios Related to Submarine Volcanic-Hydrothermal Activity and Advanced Monitoring Strategies: A Study Case from the Panarea Volcanic Group (Aeolian Islands, Italy)." Geofluids 2019 (October 13, 2019): 1–15. http://dx.doi.org/10.1155/2019/8728720.
Full textAbstract:
Geohazards associated to submarine hydrothermal systems still represent a tricky enigma to face and solve for the scientific community. The poor knowledge of a submarine environment, the rare and scarce monitoring activities, and the expensive and sometimes complicated logistics are the main problems to deal with. The submarine low-energy explosion, which occurred last November 3, 2002, off the volcanic island of Panarea, highlighted the absence of any hazard scenario to be used to manage the volcanic crisis. The “unrest” of the volcanic activity was triggered by a sudden input of deep magmatic fluids, which caused boiling water at the sea surface with a massive CO2 release besides changes in the fluids’ geochemistry. That event dramatically pushed scientists to develop new methods to monitor the seafloor venting activity. Coupling the information from geochemical investigations and data collected during the unrest of volcanic activity, we were able to (a) develop theoretical models to gain a better insight on the submarine hydrothermal system and its relationships with the local volcanic and tectonic structures and (b) to develop a preliminary submarine volcanic hazard assessment connected to the Panarea system (Aeolian Islands). In order to mitigate the potential submarine volcanic hazard, three different scenarios are described here: (1) ordinary hydrothermal venting, (2) gas burst, and (3) volcanic eruption. The experience carried out at Panarea demonstrates that the best way to face any submarine volcanic-hydrothermal hazard is to improve the collection of data in near real-time mode by multidisciplinary seafloor observatories and to combine it with periodical sampling activity.
17
Karstens, Jens, Karim Kelfoun, Sebastian F. L. Watt, and Christian Berndt. "Combining 3D seismics, eyewitness accounts and numerical simulations to reconstruct the 1888 Ritter Island sector collapse and tsunami." International Journal of Earth Sciences 109, no. 8 (April 18, 2020): 2659–77. http://dx.doi.org/10.1007/s00531-020-01854-4.
Full textAbstract:
Abstract The 1888 Ritter Island volcanic sector collapse triggered a regionally damaging tsunami. Historic eyewitness accounts allow the reconstruction of the arrival time, phase and height of the tsunami wave at multiple locations around the coast of New Guinea and New Britain. 3D seismic interpretations and sedimentological analyses indicate that the catastrophic collapse of Ritter Island was preceded by a phase of deep-seated gradual spreading within the volcanic edifice and accompanied by a submarine explosive eruption, as the volcanic conduit was cut beneath sea level. However, the potential impact of the deep-seated deformation and the explosive eruption on tsunami genesis is unclear. For the first time, it is possible to parameterise the different components of the Ritter Island collapse with 3D seismic data, and thereby test their relative contributions to the tsunami. The modelled tsunami arrival times and heights are in good agreement with the historic eyewitness accounts. Our simulations reveal that the tsunami was primarily controlled by the displacement of the water column by the collapsing cone at the subaerial-submarine boundary and that the submerged fraction of the slide mass and its mobility had only a minor effect on tsunami genesis. This indicates that the total slide volume, when incorporating the deep-seated deforming mass, is not directly scalable for the resulting tsunami height. Furthermore, the simulations show that the tsunamigenic impact of the explosive eruption energy during the Ritter Island collapse was only minor. However, this relationship may be different for other volcanogenic tsunami events with smaller slide volumes or larger magnitude eruptions, and should not be neglected in tsunami simulations and hazard assessment.
18
Portner, Ryan A., Brian M. Dreyer, and David A. Clague. "Mid-ocean-ridge rhyolite (MORR) eruptions on the East Pacific Rise lack the fizz to pop." Geology 49, no. 4 (November 20, 2020): 377–81. http://dx.doi.org/10.1130/g47820.1.
Full textAbstract:
Abstract Eruptions on the Alarcon Rise segment of the northern East Pacific Rise (23.55°N, 108.42°W) at 2500–2200 m below sea level (mbsl) produced the most compositionally diverse volcanic suite found along the submarine mid-ocean-ridge (MOR) system, offering an opportunity to compare mafic through silicic eruption styles at the same abyssal depth. Eruption styles that formed evolved volcanic rocks on the submarine MOR have not been studied in detail. The prevalence of lava flows along the MOR indicates that most eruptions are nonexplosive, but some volcaniclastic characteristics suggest that explosive styles also occur. Higher viscosities in intermediate (103–5 Pa·s) versus mafic (101 Pa·s) lavas on Alarcon Rise correspond with larger, more brecciated pillows, while highly viscous rhyolite lavas (106–7 Pa·s) formed rugged domes mostly composed of autoclastic breccia. Although high H2O contents (1.5–2.1 wt%), abundant volcaniclasts, and vesicularities up to 53% in rhyolite might imply eruption explosivity, limited fine-grained ash production and dispersal indicate an effusive origin. Higher viscosities of MOR rhyolite (MORR) magma and small eruption volumes, compared to MOR basalt (MORB), limit bubble coalescence and rapid magma ascent, two likely prerequisites for deep-marine eruption explosivity. This idea is supported by widespread dispersal of basaltic ash, but very limited production and dispersal of silicic ash on Alarcon Rise.
19
Thurin, Julien, Carl Tape, and Ryan Modrak. "Multi-Event Explosive Seismic Source for the 2022 Mw 6.3 Hunga Tonga Submarine Volcanic Eruption." Seismic Record 2, no. 4 (October 1, 2022): 217–26. http://dx.doi.org/10.1785/0320220027.
Full textAbstract:
Abstract The eruption of the Hunga Tonga–Hunga Ha’apai submarine volcano on 15 January 2022 produced a variety of geophysical responses, including a significant seismic signal. We study the seismic source process of this event by inverting for moment tensors (MTs) using regional surface waves (Rayleigh, Love). By comparing inversion results for the eruption with eight nearby earthquakes, we show that it is possible to discriminate MT source types. Our inversion yields a shallow explosive source for the eruption and reveals the importance of trade-offs among depth, magnitude, and source type. We illustrate these trade-offs by representing the misfit variations over the eigenvalue lune. Finally, we invert for the source-time function of the sequence of explosions that occurred in the first minutes of the eruption. The multi-event source-time function comprises four subevents spanning ∼270 s, with a total magnitude estimate of Mw 6.34 ± 0.10.
20
Kakinuma, Taro, Hiroshi Matsumoto, Kei Yamashita, and Yudai Yanagi. "TSUNAMI GENERATION DUE TO SUBMARINE VOLCANIC ERUPTIONS WITH PHREATOMAGMATIC EXPLOSION OR CALDERA SUBSIDENCE." Coastal Engineering Proceedings 1, no. 34 (October 30, 2014): 17. http://dx.doi.org/10.9753/icce.v34.currents.17.
Full text
21
Caracausi, A., M. Ditta, F. Italiano, M. Longo, P. M. Nuccio, and A. Paonita. "Massive submarine gas output during the volcanic unrest off Panarea Island (Aeolian arc, Italy): Inferences for explosive conditions." GEOCHEMICAL JOURNAL 39, no. 5 (2005): 459–67. http://dx.doi.org/10.2343/geochemj.39.459.
Full text
22
Casalbore, Daniele, Federico Di Traglia, Claudia Romagnoli, Massimiliano Favalli, Teresa Gracchi, Carlo Tacconi Stefanelli, Teresa Nolesini, et al. "Integration of Remote Sensing and Offshore Geophysical Data for Monitoring the Short-Term Morphological Evolution of an Active Volcanic Flank: A Case Study from Stromboli Island." Remote Sensing 14, no. 18 (September 15, 2022): 4605. http://dx.doi.org/10.3390/rs14184605.
Full textAbstract:
The Sciara del Fuoco (SdF) collapse scar at Stromboli is an active volcanic area affected by rapid morphological changes due to explosive/effusive eruptions and mass-wasting processes. The aim of this paper is to demonstrate the importance of an integrated analysis of multi-temporal remote sensing (photogrammetry, COSMO-SkyMed Synthetic Aperture Radar amplitude image) and marine geophysical data (multibeam and side scan sonar data) to characterize the main morphological, textural, and volumetric changes that occurred along the SdF slope in the 2020–2021 period. The analysis showed the marked erosive potential of the 19 May 2021 pyroclastic density current generated by a crater rim collapse, which mobilized a minimum volume of 44,000 m3 in the upper Sciara del Fuoco slope and eroded 350,000–400,000 m3 of material just considering the shallow-water setting. The analysis allowed us also to constrain the main factors controlling the emplacement of different lava flows and overflows during the monitored period. Despite the morphological continuity between the subaerial and submarine slope, textural variations in the SdF primarily depend on different processes and characteristics of the subaerial slope, the coastal area, the nearshore, and “deeper” marine areas.
23
Ferrer, Mercedes, Luis González de Vallejo, José Madeira, César Andrade, Juan C. García-Davalillo, Maria da Conceição Freitas, Joaquín Meco, Juan F. Betancort, Trinidad Torres, and José Eugenio Ortiz. "Megatsunamis Induced by Volcanic Landslides in the Canary Islands: Age of the Tsunami Deposits and Source Landslides." GeoHazards 2, no. 3 (August 12, 2021): 228–56. http://dx.doi.org/10.3390/geohazards2030013.
Full textAbstract:
Evidence for frequent, large landslides on the flanks of the volcanic edifices forming the Canary Islands include outstanding landslide scars and their correlative submarine and subaerial rock and debris avalanche deposits. These landslides involved volumes ranging from tens to hundreds of km3. The sudden entry of large volumes of rock masses in the sea may have triggered tsunamis capable of affecting the source and neighboring islands, with the resulting huge waves dragging coastal and seabed materials and fauna and redepositing them inland. Here, we present new geological evidence and geochronological data of at least five megatsunamis in Tenerife, Lanzarote, and Gran Canaria, triggered by island flank megalandslides, and occasionally explosive eruptions, during the last 1 million years. The exceptional preservation of the megatsunami deposits and the large area they cover, particularly in Tenerife, provide fundamental data on the number of tsunami events and run-ups, and allow proposals on the sources and age of the tsunamis. Tsunami run-up heights up to 290 m above coeval sea level, some of the highest known on Earth in recent geological times, were estimated based on sedimentological, geomorphological, paleontological, and geochronological data. The research results made it possible to estimate the recurrence of tsunamis in the archipelago during the last hundreds of thousands of years, and to establish relationships between tsunami deposits and the probable triggering island flank landslides.
24
Troll, V. R., A. Klügel, M. A. Longpré, S. Burchardt, F. M. Deegan, J. C. Carracedo, S. Wiesmaier, et al. "Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption." Solid Earth 3, no. 1 (March 13, 2012): 97–110. http://dx.doi.org/10.5194/se-3-97-2012.
Full textAbstract:
Abstract. A submarine eruption started off the south coast of El Hierro, Canary Islands, on 10 October 2011 and continues at the time of this writing (February 2012). In the first days of the event, peculiar eruption products were found floating on the sea surface, drifting for long distances from the eruption site. These specimens, which have in the meantime been termed "restingolites" (after the close-by village of La Restinga), appeared as black volcanic "bombs" that exhibit cores of white and porous pumice-like material. Since their brief appearance, the nature and origin of these "floating stones" has been vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have analysed the textures and compositions of representative "restingolites" and compared the results to previous work on similar rocks found in the Canary Islands. Based on their high-silica content, the lack of igneous trace element signatures, the presence of remnant quartz crystals, jasper fragments and carbonate as well as wollastonite (derived from thermal overprint of carbonate) and their relatively high oxygen isotope values, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary layers that were picked up and heated by the ascending magma, causing them to partially melt and vesiculate. As they are closely resembling pumice in appearance, but are xenolithic in origin, we refer to these rocks as "xeno-pumice". The El Hierro xeno-pumices hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies beneath the Canary Islands as well as in similar Atlantic islands that rest on sediment-covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of "restingolites" indicates that crustal recycling is a relevant process in ocean islands, too, but does not herald the arrival of potentially explosive high-silica magma in the active plumbing system beneath El Hierro.
25
Talandier, Jacques, Olivier Hyvernaud, Hélène Hébert, René C. Maury, and Sébastien Allgeyer. "Seismic and hydroacoustic effects of the May 29, 2010 submarine South Sarigan volcanic explosion: Energy release and interpretation." Journal of Volcanology and Geothermal Research 394 (April 2020): 106819. http://dx.doi.org/10.1016/j.jvolgeores.2020.106819.
Full text
26
Picard, Christian, and Michel Piboule. "Pétrologie des roches volcaniques du sillon de roches vertes archéennes de Matagami – Chibougamau à l'ouest de Chapais (Abitibi est, Québec).1. Le groupe basal de Roy." Canadian Journal of Earth Sciences 23, no. 4 (April 1, 1986): 561–78. http://dx.doi.org/10.1139/e86-056.
Full textAbstract:
In the northeastern part of the Abitibi orogenic belt, the Archean Matagami–Chibougamou greenstone belt (2700 Ma) includes a basal volcanic sequence named the Roy Group, unconformably overlain by a volcano-sedimentary series called the Opemisca Group.The Roy Group, to the west of the town of Chapais, consists of a thick, stratified, and polycyclic volcanic series (thickness = 11 000 m) resembling the large, western Abitibi submarine stratovolcanoes constructed by three mafic to felsic magmatic cycles. The first cycle (Chrissie Formation) shows lateral spreading and is composed only of a meta-andesite and felsic pyroclastite sequence of calc-alkaline affinity. The other two cycles (Obatogamau and Waconichi formations; then Gilman, Blondeau, and Scorpio formations) are characterized by a sequence of repeated MORB type basaltic lava flows of tholeiitic affinity and by intermediate to acid lava and pyroclastic sequences calc-alkaline affinity.The stratigraphic and petrographic data suggest emplacement of mafic lavas on an abyssal plain (Obatogamau Formation) or at a later time on the flanks of a large submarine volcanic shield (Gilman and Blondeau formations). The lava and felsic pyroclastite flows were formed by very explosive eruptions from central spreading type volcanoes above a pre-existing continental crust. In particular, the Scorpio volcanic rocks were emplaced on volcanic islands later dismantled by erosion.The contents and distribution of trace elements and rare earths show that basaltic lavas resulted from an equilibrium partial melting (F = 15–35%) of spinel lherzolite type mantle sources depleted to weakly enriched in Th, Ta, Nb, and light rare-earth elements (LREE), and from fractional crystallization at low pressure of feldspar, clinopyroxene, and olivine. The lavas and the felsic pyroclastites of the Waconichi and Scorpio formations appear to result from partial melting of a mantle source of lherzolite type enriched in LREE and involving some garnet. At a late stage, the melts were probably contaminated by some continental crust materials and then differentiated by fractional crystallization of plagioclase, amphibole, biotite, and magnetite. The lavas in the Chrissie Formation and the middle member of the Gilman Formation seem to result from partial melting of a mantle source enriched in LREE with a composition between the two described above. They were subsequently modified by fractional crystallization of the plagioclase, clinopyroxene, olivine, and titanomagnetite.In general, the mafic to felsic magmatic cycles observed are characterized by a thick sequence of repeated tholeiitic basalt flows similar to those of modern mid-oceanic ridges and by a lava and felsic pyroclastite sequence of calc-alkaline affinity comparable to those occurring in orogenic belts. The transition from one lava sequence to another is marked by a significant chemical discontinuity, and the mantle sources exhibit an increasing enrichment in LREE during a given magmatic cycle. A model is proposed to satisfactorily explain all the stratigraphic, petrographic, and geochemical data implying a hot spot type mechanism, which could be responsible for the cyclic, rising diapirs inside the stratified Archean mantle and for initiating the repeated mantle source meltings, depleted and enriched in LREE, respectively. [Journal Translation]
27
Troll, V. R., A. Klügel, M. A. Longpré, S. Burchardt, F. M. Deegan, J. C. Carracedo, S. Wiesmaier, et al. "Floating sandstones off El Hierro (Canary Islands, Spain): the peculiar case of the October 2011 eruption." Solid Earth Discussions 3, no. 2 (December 1, 2011): 975–99. http://dx.doi.org/10.5194/sed-3-975-2011.
Full textAbstract:
Abstract. The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These specimens appeared as floating volcanic "bombs" that have in the meantime been termed "restingolites" (after the close-by village of La Restinga) and exhibit cores of white and porous pumice-like material. Currently the nature and origin of these "floating stones" is vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element signatures, and the presence of remnant quartz crystals, jasper fragments and carbonate relicts, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of these "restingolites" does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption.
28
Jackson, Marie D., Magnús T. Gudmundsson, Tobias B. Weisenberger, J. Michael Rhodes, Andri Stefánsson, Barbara I. Kleine, Peter C. Lippert, et al. "SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption." Scientific Drilling 25 (June 12, 2019): 35–46. http://dx.doi.org/10.5194/sd-25-35-2019.
Full textAbstract:
Abstract. The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve.
29
Jackson, Marie D. "Petrograpic and material observations of basaltic lapilli tuff, 1979 and 2017 Surtsey drill cores, Iceland." Surtsey research 14 (June 2020): 47–62. http://dx.doi.org/10.33112/surtsey.14.4.
Full textAbstract:
Petrographic studies of thin sections from the 1979 and 2017 Surtsey drill cores provide new insights into microstructural features in basaltic lapilli tuff sampled from the principal structural and hydrothermal zones of the volcano. These describe narrow rims of fine ash on altered glass pyroclasts in thin sections of the 2017 cores, characteristics of granular and microtubular structures in the original thin sections of the 1979 core, and glass alteration in diverse environments. The narrow ash rims follow the outlines of glass pyroclasts in the subaerial tuff cone and in submarine and sub-seafloor deposits; they suggest complex eruptive and depositional processes. The tubular microstructures resemble endolithic microborings in older oceanic basalt; they suggest possible microbial activity. Tubule lengths indicate rapid growth rates, up to 30 µm in ~15 years. Comparisons of glass alteration in thin sections prepared immediately after drilling in 1979 and 2017 indicate differential time-lapse alteration processes in the structural and hydrothermal zones of the volcano. In contrast, thin sections of the 1979 core prepared after 38 years in the repository reveal labile glass alteration during archival storage. The oven-dry density of the sub-seafloor lapilli tuff decreases in 2017 samples with high porosity and water absorption and increases in 2017 samples with a compact ash matrix and lower water absorption. The petrographic descriptions and material measurements provide a foundational reference for further investigations of explosive eruption and deposition of basaltic tephra at Surtsey and the subsequent alteration of these deposits in the volcanic environment and, potentially, the curatorial environment.
30
Koulakov, Ivan, Vera Schlindwein, Mingqi Liu, Taras Gerya, Andrey Jakovlev, and Aleksey Ivanov. "Low-degree mantle melting controls the deep seismicity and explosive volcanism of the Gakkel Ridge." Nature Communications 13, no. 1 (June 3, 2022). http://dx.doi.org/10.1038/s41467-022-30797-4.
Full textAbstract:
AbstractThe world’s strongest known spreading-related seismicity swarm occurred in 1999 in a segment of the Gakkel Ridge located at 85°E as a consequence of an effusive-explosive submarine volcanic eruption. The data of a seismic network deployed on ice floes were used to locate hundreds of local earthquakes down to ∼25 km depth and to build a seismic tomography model under the volcanic area. Here we show the seismicity and the distribution of seismic velocities together with the 3D magmatic-thermomechanical numerical model, which demonstrate how a magma reservoir under the Gakkel Ridge may form, rise and trigger volcanic eruptions in the rift valley. The ultraslow spreading rates with low mantle potential temperatures appear to be a critical factor in the production of volatile-rich, low-degree mantle melts that are focused toward the magma reservoirs within narrow magmatic sections. The degassing of these melts is the main cause of the explosive submarine eruptions.
31
Carn, S. A., N. A. Krotkov, B. L. Fisher, and C. Li. "Out of the blue: Volcanic SO2 emissions during the 2021–2022 eruptions of Hunga Tonga—Hunga Ha’apai (Tonga)." Frontiers in Earth Science 10 (September 13, 2022). http://dx.doi.org/10.3389/feart.2022.976962.
Full textAbstract:
Most volcanism on Earth is submarine, but volcanic gas emissions by submarine eruptions are rarely observed and hence largely unquantified. On 15 January 2022 a submarine eruption of Hunga Tonga-Hunga Ha’apai (HTHH) volcano (Tonga) generated an explosion of historic magnitude, and was preceded by ∼1 month of Surtseyan eruptive activity and two precursory explosive eruptions. We present an analysis of ultraviolet (UV) satellite measurements of volcanic sulfur dioxide (SO2) between December 2021 and the climactic 15 January 2022 eruption, comprising an unprecedented record of Surtseyan eruptive emissions. UV measurements from the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite, the Ozone Mapping and Profiler Suite (OMPS) on Suomi-NPP, the Tropospheric Monitoring Instrument (TROPOMI) on ESA’s Sentinel-5P, and the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) are combined to yield a consistent multi-sensor record of eruptive degassing. We estimate SO2 emissions during the eruption’s key phases: the initial 19 December 2021 eruption (∼0.01 Tg SO2); continuous SO2 emissions from 20 December 2021—early January 2022 (∼0.12 Tg SO2); the 13 January 2022 stratospheric eruption (0.06 Tg SO2); and the paroxysmal 15 January 2022 eruption (∼0.4–0.5 Tg SO2); yielding a total SO2 emission of ∼0.6–0.7 Tg SO2 for the eruptive episode. We interpret the vigorous SO2 emissions observed prior to the January 2022 eruptions, which were significantly higher than measured in the 2009 and 2014 HTHH eruptions, as strong evidence for a rejuvenated magmatic system. High cadence DSCOVR/EPIC SO2 imagery permits the first UV-based analysis of umbrella cloud spreading and volume flux in the 13 January 2022 eruption, and also tracks early dispersion of the stratospheric SO2 cloud injected on January 15. The ∼0.4–0.5 Tg SO2 discharged by the paroxysmal 15 January 2022 HTHH eruption is low relative to other eruptions of similar magnitude, and a review of other submarine eruptions in the satellite era indicates that modest SO2 yields may be characteristic of submarine volcanism, with the emissions and atmospheric impacts likely dominated by water vapor. The origin of the low SO2 loading awaits further investigation but scrubbing of SO2 in the water-rich eruption plumes and rapid conversion to sulfate aerosol are plausible, given the exceptional water emission by the 15 January 2022 HTHH eruption.
32
Carazzo, G., E. Kaminski, and S. Tait. "On the rise of turbulent plumes: Quantitative effects of variable entrainment for submarine hydrothermal vents, terrestrial and extra terrestrial explosive volcanism." Journal of Geophysical Research 113, B9 (September 3, 2008). http://dx.doi.org/10.1029/2007jb005458.
Full text
33
Pakoksung, Kwanchai, Anawat Suppasri, and Fumihiko Imamura. "The near-field tsunami generated by the 15 January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano and its impact on Tongatapu, Tonga." Scientific Reports 12, no. 1 (September 7, 2022). http://dx.doi.org/10.1038/s41598-022-19486-w.
Full textAbstract:
AbstractOn 15 January 2022 at 04:15 UTC, the Hunga Tonga-Hunga Ha’apai (HTHH) volcano in Tonga produced a massive eruption that triggered a transoceanic tsunami generated by the coupled ocean and atmospheric shock wave produced during the explosion. The tsunami first reached the coast of Tonga and eventually reached many coasts around the world. This volcano previously underwent a massive eruption in 1100 AD, and an eruption occurs approximately every 1000 years. The 2022 HTHH event provides an opportunity to study a major volcanically generated tsunami that caused substantial damage. In this study, we present a numerical simulation of a tsunami with a state-of-the-art numerical model based on a submarine explosion scenario. We constrain the geometry and magnitude of the explosion energy source based on analyses of pre- and post-event satellite images, which demonstrate that the explosion magnitude varied from 1 to 90 megatons of trinitrotoluene (Mt). Estimated submarine explosion geometries result in a suitable explosion magnitude of approximately 25 Mt, as determined with the waveform from the tide gauge in the time and frequency domains. The tsunami wave first reached the northwestern part of Tonga’s Tongatapu within 10 min, with a maximum runup height of approximately 15 m, and covered the whole of Tongatapu within 30 min. Finally, the numerical simulation provides deep insights into the physical volcanic explosion processes and improves our understanding and forecasting capabilities of frequent and catastrophic tsunamis caused by submarine volcanic explosions.
34
Nomikou, Paraskevi, Paraskevi N. Polymenakou, Andrea Luca Rizzo, Sven Petersen, Mark Hannington, Stephanos Pantelis Kilias, Dimitris Papanikolaou, et al. "SANTORY: SANTORini’s Seafloor Volcanic ObservatorY." Frontiers in Marine Science 9 (March 31, 2022). http://dx.doi.org/10.3389/fmars.2022.796376.
Full textAbstract:
Submarine hydrothermal systems along active volcanic ridges and arcs are highly dynamic, responding to both oceanographic (e.g., currents, tides) and deep-seated geological forcing (e.g., magma eruption, seismicity, hydrothermalism, and crustal deformation, etc.). In particular, volcanic and hydrothermal activity may also pose profoundly negative societal impacts (tsunamis, the release of climate-relevant gases and toxic metal(loid)s). These risks are particularly significant in shallow (<1000m) coastal environments, as demonstrated by the January 2022 submarine paroxysmal eruption by the Hunga Tonga-Hunga Ha’apai Volcano that destroyed part of the island, and the October 2011 submarine eruption of El Hierro (Canary Islands) that caused vigorous upwelling, floating lava bombs, and natural seawater acidification. Volcanic hazards may be posed by the Kolumbo submarine volcano, which is part of the subduction-related Hellenic Volcanic Arc at the intersection between the Eurasian and African tectonic plates. There, the Kolumbo submarine volcano, 7 km NE of Santorini and part of Santorini’s volcanic complex, hosts an active hydrothermal vent field (HVF) on its crater floor (~500m b.s.l.), which degasses boiling CO2–dominated fluids at high temperatures (~265°C) with a clear mantle signature. Kolumbo’s HVF hosts actively forming seafloor massive sulfide deposits with high contents of potentially toxic, volatile metal(loid)s (As, Sb, Pb, Ag, Hg, and Tl). The proximity to highly populated/tourist areas at Santorini poses significant risks. However, we have limited knowledge of the potential impacts of this type of magmatic and hydrothermal activity, including those from magmatic gases and seismicity. To better evaluate such risks the activity of the submarine system must be continuously monitored with multidisciplinary and high resolution instrumentation as part of an in-situ observatory supported by discrete sampling and measurements. This paper is a design study that describes a new long-term seafloor observatory that will be installed within the Kolumbo volcano, including cutting-edge and innovative marine-technology that integrates hyperspectral imaging, temperature sensors, a radiation spectrometer, fluid/gas samplers, and pressure gauges. These instruments will be integrated into a hazard monitoring platform aimed at identifying the precursors of potentially disastrous explosive volcanic eruptions, earthquakes, landslides of the hydrothermally weakened volcanic edifice and the release of potentially toxic elements into the water column.
35
Newland, Eric L., Nicola Mingotti, and Andrew W. Woods. "Dynamics of deep-submarine volcanic eruptions." Scientific Reports 12, no. 1 (February 28, 2022). http://dx.doi.org/10.1038/s41598-022-07351-9.
Full textAbstract:
AbstractDeposits from explosive submarine eruptions have been found in the deep sea, 1–4 km below the surface, with both flow and fall deposits extending several km’s over the seafloor. A model of a turbulent fountain suggests that after rising 10–20 m above the vent, the erupting particle-laden mixture entrains and mixes with sufficient seawater that it becomes denser than seawater. The momentum of the resulting negatively buoyant fountain is only sufficient to carry the material 50–200 m above the seafloor and much of the solid material then collapses to the seafloor; this will not produce the far-reaching fall deposits observed on the seabed. However, new laboratory experiments show that particle sedimentation at the top of the fountain enables some of the hot, buoyant water in the fountain to separate from the collapsing flow and continue rising as a buoyant plume until it forms a radially spreading intrusion higher in the water column. With eruption rates of 10$$^6$$ 6 –10$$^7$$ 7 $$\hbox {kg s}^{-1}$$ kg s - 1 , we estimate that this warm water may rise a few 100’s m above the fountain. Some of the finer grained pyroclasts can be carried upwards by this flow and as they spread out in the radial intrusion, they gradually sediment to form a fall deposit which may extend 1000’s m from the source. Meanwhile, material collapsing from the dense fountain forms aqueous pyroclastic flows which may also spread 1000’s m from the vent forming a flow deposit on the seabed. Quantification of the controls on the concurrent fall and flow deposits, and comparison with field observations, including from the 2012 eruption of Havre Volcano in the South Pacific, open the way to new understanding of submarine eruptions.
36
Nam, Kounghoon, Fawu Wang, Kongming Yan, and Guolong Zhu. "Characteristics and time-series monitoring by GOES-17 of volcano flume on 15 January 2022 from Tonga submarine volcanic eruption." Geoenvironmental Disasters 10, no. 1 (January 23, 2023). http://dx.doi.org/10.1186/s40677-023-00232-x.
Full textAbstract:
Abstract Background On 15 January 2022, a submarine volcanic eruption occurred at Hunga Tonga. Time-series monitoring from the Geostationary Operational Environmental Satellite (GOES-17) was analysed to estimate the magnitude, location, start time, and duration of the eruption and to measure the evolving characteristics of Hunga Ha’apai Island. Results The eruption starting time was between 04:10 and 04:20 UTC with an eruption intensity that increased drastically and produced a plume that reached a maximum height of about 58 km. The explosive phase lasted 13 h and consisted of multiple steam and tephra explosions with an M 5.8 earthquake. The Airmass RGB, which combines water vapor and infrared imagery from the ABI and was used to monitor the evolution of the volcano, captured a plume of gases from the eruption of Hunga Tonga volcano on 15 January 2022. This type of imagery provides information on the middle and upper levels of the troposphere and distinguishes between high- and mid-level clouds. Conclusion A sonic explosion also occurred, possibly when the volcano collapsed underwater and seawater rushed in, causing a huge displacement of seawater. The Hunga Tonga–Hunga Ha’apai eruption is not over and could worsen in the coming days. Future studies are required to assess the potential effects on stratospheric chemistry and radiation for secondary damage analysis.
37
Terry, James P., James Goff, Nigel Winspear, Vena Pearl Bongolan, and Scott Fisher. "Tonga volcanic eruption and tsunami, January 2022: globally the most significant opportunity to observe an explosive and tsunamigenic submarine eruption since AD 1883 Krakatau." Geoscience Letters 9, no. 1 (June 28, 2022). http://dx.doi.org/10.1186/s40562-022-00232-z.
Full textAbstract:
AbstractJanuary 2022 witnessed the violent eruption of Hunga Tonga–Hunga Haʻapai submarine volcano in the South Pacific. With a volcanic explosivity index possibly equivalent to VEI 5, this represents the largest seaborne eruption for nearly one and a half centuries since Indonesia’s cataclysmic explosion of Krakatau in AD 1883. The Tongan eruption remarkably produced ocean-wide tsunamis, never documented before in the Pacific instrumental record. Volcanically generated tsunamis have been referred to as a ‘blind spot’ in our understanding of tsunami hazards, particularly in the Pacific Ocean. This event therefore presents a unique opportunity for investigating the multiple processes contributing to volcanic tsunamigenesis. It is argued that, although challenges exist, integrating theoretical, observational, field and modelling techniques offers the best approach to improving volcanic tsunami hazard assessment across Oceania.
38
Sonder, Ingo, and Pranabendu Moitra. "Experimental constraints on the stability and oscillation of water vapor film—a precursor for phreatomagmatic and explosive submarine eruptions." Frontiers in Earth Science 10 (October 3, 2022). http://dx.doi.org/10.3389/feart.2022.983112.
Full textAbstract:
Pre-mixing of magma and external water plays a key role in driving explosive phreatomagmatic and submarine volcanic eruptions. A thin film of water vapor forms at the magma–water interface as soon as hot magma comes in direct contact with the cold water (Leidenfrost effect). The presence of a stable vapor film drives efficient mixing and mingling between magma and water, as well as magma and wet and water-saturated sediments. Such mixing occurs before explosive molten fuel–coolant type interactions. Using high-temperature laboratory experiments, we investigate the effect of magma and water temperatures on the stability of vapor film, which has not been performed systematically for a magmatic heat source. The experiments were performed with re-melted volcanic rock material, from which spherically-shaped rock samples were produced. These samples were heated to 1,110°C and then submerged in a water pool with a constant temperature (3–93°C). The experiments were recorded on video, and, synchronously, sample and water temperatures were measured using thermocouples. The time-dependent thickness of the vapor film was measured from the video material. The vapor film tends to oscillate with time on the order of 102 Hz. We find that the vertical collapse rates of vapor films along the sample–water interfaces are 13.7 mm s−1 and 4.2 mm s−1 for water temperatures of 3.0°C and 65°C, respectively. For a given initial sample temperature, the thickness and stability time scales decrease with decreasing water temperature, which has implications for the efficiency of pre-mixing required for explosive eruptions. Using thermodynamics and previously measured material parameters, it is shown that a sudden collapse of the vapor film can start brittle fragmentation of the melt and thus serves as the starting point of thermohydraulic explosions.
39
Yeo, I. A., I. M. McIntosh, S. E. Bryan, K. Tani, M. Dunbabin, D. Metz, P. C. Collins, K. Stone, and M. S. Manu. "The 2019–2020 volcanic eruption of Late’iki (Metis Shoal), Tonga." Scientific Reports 12, no. 1 (May 6, 2022). http://dx.doi.org/10.1038/s41598-022-11133-8.
Full textAbstract:
AbstractLate’iki (previously known as Metis Shoal) is a highly active volcano in the Tofua arc with at least four temporary island-building eruptions and one submarine eruption in the last 55 years. The most recent eruption, commencing in October 2019, resulted in lava effusion and subsequent phreatic explosions, the construction of a short-lived island that was quickly eroded by wave action and possibly further phreatic activity that continued into January 2020. The two-pyroxene dacite from the 2019 eruption is similar to the 1967/8 eruptions suggesting the magma is residual from earlier eruptions and has not undergone further differentiation in the last 50 years. New observations of the 2019 eruption site confirm the lava-dominant character of the volcano summit but a thin veneer of wave-reworked, finely fragmented lava material remains that is interpreted to have been produced by phreatic explosions from hot rock-water interactions during the effusive eruption. A notable absence of quench-fragmented hyaloclastite breccias suggests that non-explosive quench fragmentation processes were minimal at these shallow depths or that hyaloclastite debris has resedimented to greater depths beyond our summit survey area.
40
Soule, S. Adam, Michael Zoeller, and Carolyn Parcheta. "Submarine lava deltas of the 2018 eruption of Kīlauea volcano." Bulletin of Volcanology 83, no. 4 (March 11, 2021). http://dx.doi.org/10.1007/s00445-020-01424-1.
Full textAbstract:
AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.
41
McIntosh, Iona M., Kaori Aoki, Taiki Yanagishima, Makoto Kobayashi, Masanori Murata, and Takehiko Suzuki. "Reconstruction of submarine eruption processes from FTIR volatile analysis of marine tephra: Example of Oomurodashi volcano, Japan." Frontiers in Earth Science 10 (December 13, 2022). http://dx.doi.org/10.3389/feart.2022.963392.
Full textAbstract:
Tephra layers in marine sediments are widely used to correlate and date paleoclimate and paleoceanography records, and to determine spatiotemporal changes in magmatic evolution and eruption frequency. Dissolved matrix glass H2O contents of marine tephra could potentially inform understanding of eruption processes but are rarely used due to the issue of secondary hydration after deposition. Recent advancements in Fourier transform infrared spectroscopy (FTIR) volatile analysis have enabled reconstruction of original water contents of hydrated volcanic glasses. These new Fourier transform infrared spectroscopy analysis methods offer a new way to investigate tephra stored in marine sedimentary archives. We present a case study of the Od-1 tephra layer in marine sedimentary core C9010E, drilled ∼40 km south of the Boso peninsula in Japan. This tephra was erupted by the shallow silicic submarine Oomurodashi volcano in the northern Izu-Bonin arc at ∼13.5 ka. Our Fourier transform infrared spectroscopy volatile data show it has been affected by secondary hydration, with the extent of hydration controlled by grain size and porosity characteristics. Numerical modelling of low temperature hydration suggests Fourier transform infrared spectroscopy data offer an additional method for estimating eruption ages of marine tephra. OH contents, unaltered by low temperature secondary hydration, record low ambient eruptive pressures for all grain sizes and tephra types i.e., blocky and dense or pumiceous. Consideration of hydrostatic pressure gradients and past sea level at Oomurodashi shows that the majority of tephra volatile data cannot be explained by quench within a submarine eruption plume. Instead, OH contents record quench fragmentation within the shallow submarine edifice. Physical characteristics of the tephra are consistent with the formation of these tephra by explosive phreatomagmatic eruption processes. Together these OH data and tephra characteristics support the interpretation that the Od-1 tephra layer was formed by the same shallow phreatomagmatic eruption that formed the existing Oomuro Hole crater and that produced subaerial tephra deposits on nearby Izu-Oshima and Toshima islands. This study demonstrates the crucial contribution that imaging Fourier transform infrared spectroscopy analysis can make to the interpretation of degassing and eruption processes of volcanic glasses, particularly vesicular pyroclasts and/or glasses affected by secondary hydration, adding an important new dimension to marine tephra research.
42
Matsumoto, Hiroyuki, Mario Zampolli, Georgios Haralabus, Jerry Stanley, James Robertson, and Nurcan Meral Özel. "Hydroacoustic Signals Originating from Marine Volcanic Activity at Kadovar Island, Papua New Guinea, Recorded by the Comprehensive Nuclear-Test-Ban Treaty International Monitoring System." Pure and Applied Geophysics, July 24, 2022. http://dx.doi.org/10.1007/s00024-022-03096-8.
Full textAbstract:
AbstractHydroacoustic signals originating from marine volcanic activity at Kadovar Island (Papua New Guinea), recorded by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System (IMS) hydroacoustic (HA) station HA11 Wake Island (USA), are examined herein. Episodes of high volcanic activity were identified on two occasions, separated by a period of 1 month. The events studied pertain to an initial eruption series during a period between January and February 2018. Based on local visual observations, the Kadovar volcano began to erupt at the summit and then created a new vent spot near the coast. This series of events also included the collapse of a lava dome. Direction-of-arrival estimates for the hydroacoustic signals detected at HA11 were computed using a cross-correlation technique, which allowed for the discrimination between hydroacoustic signals originating from the Kadovar volcanic activity and numerous other hydroacoustic signals attributed to seismic activity in the Pacific Ocean. The Kadovar-related seismic signals could not be identified by regional IMS seismic stations, suggesting a submarine origin of these events. On the other hand, hydroacoustic signals originating from the Kadovar volcanic activity were identified by the seismometer at Manus Island, which is located between Kadovar and HA11. The study suggests that a series of explosive bursts followed by an unusual rumble and a broadband signal plus rumble may constrain the time of the lava dome collapse event at Kadovar Island to 00:30 UTC, 00:33 UTC, and 00:46 UTC on 09 February 2018. Given the compatibility of this observation with the tsunami generation reported by eyewitnesses on the nearby island of Blup Blup, the authors interpret this particular hydroacoustic signal as being a remote observation of this tsunamigenic event. The objective of this study was to assess the potential added value of IMS hydroacoustic data for remote surveillance of geohazards in otherwise sparsely monitored areas.
43
Knafelc, J., D. Gust, S. E. Bryan, M. Anderson, and H. E. Cathey. "Petrogenesis of Havre Volcano in the Kermadec Arc: 2012 Eruption of a Chemically Homogeneous Rhyolite." Frontiers in Earth Science 10 (August 17, 2022). http://dx.doi.org/10.3389/feart.2022.886897.
Full textAbstract:
The 2012 Havre submarine eruption produced a 1.5 km3 bulk rock volume or 0.52 km3 dense rock equivalent volume of rhyolite emplaced as minor lava flows, a field of sunken seafloor pumice, and a volumetrically dominant pumice raft. This moderately large volume of medium-K (1.4–1.6 wt% K2O) rhyolite pumice is relatively chemically homogeneous (71.5–73.0 wt% SiO2), and no trace element variation or cryptic zoning has been detected despite the textural diversity of pumice material. Radiogenic isotope ratios (87Sr/86Sr 0.703693–0.703744; 206Pb/204Pb 18.7648–18.7781; 208Pb/204Pb 38.587–38.605; 143Nd/144Nd 0.513001–0.513020) demonstrate the Havre rhyolite is sourced from mantle similar to regional eruptive products of the Kermadec arc volcanic front. Providing some further insight into the Havre magmatic system is an abundance of diverse volcanic rock fragments primarily embedded in the banded raft pumice. Embedded rock fragments represent a variety of fresh to hydrothermally altered lavas ranging in composition from basaltic to rhyolitic (50.6–72.3 wt% SiO2) and are likely sourced from varying depths within the volcanic conduit during explosive fragmentation. The diverse embedded volcanic rock fragments, therefore, represent earlier erupted lavas that constructed Havre volcano and are snapshots of the petrogenetic history of Havre. Magnesian augite in basaltic to basaltic andesite embedded rock fragments has a similar compositional range (En55Fs12Wo33 to En39Fs26Wo35) to the previously documented antecrystic clinopyroxene observed in the 2012 rhyolite pumice raft. Herein, we explain how this large volume of chemically homogeneous crystal-poor rhyolite can be generated in an oceanic arc setting based on major and trace element petrogenetic models. Rhyolite-MELTS crystal fractionation models indicate the antecrystic mineral compositions within the Havre pumice of plagioclase (An55–78), and magnesian augites (En53Fs10Wo37 to En40Fs26Wo34) are the primary phases that would crystallize in basaltic to andesitic melt compositions. Modeling indicates that the forerunner basaltic magma must be a relatively dry (∼1 wt% H20) low-K tholeiitic basalt in composition and would require ∼78% crystallization at different pressures to ultimately generate the Havre 2012 rhyolite.
44
Cooke, Andrew, Michael Bruton, and Minosoa Ravololoharinjara. "Coelacanth discoveries in Madagascar, with recommendations on research and conservation." South African Journal of Science 117, no. 3/4 (March 29, 2021). http://dx.doi.org/10.17159/sajs.2021/8541.
Full textAbstract:
The presence of populations of the Western Indian Ocean coelacanth (Latimeria chalumnae) in Madagascar is not surprising considering the vast range of habitats which the ancient island offers. The discovery of a substantial population of coelacanths through handline fishing on the steep volcanic slopes of Comoros archipelago initially provided an important source of museum specimens and was the main focus of coelacanth research for almost 40 years. The advent of deep-set gillnets, or jarifa, for catching sharks, driven by the demand for shark fins and oil from China in the mid- to late 1980s, resulted in an explosion of coelacanth captures in Madagascar and other countries in the Western Indian Ocean. We review coelacanth catches in Madagascar and present evidence for the existence of one or more populations of L. chalumnae distributed along about 1000 km of the southern and western coasts of the island. We also hypothesise that coelacanths are likely to occur around the whole continental margin of Madagascar, making it the epicentre of coelacanth distribution in the Western Indian Ocean and the likely progenitor of the younger Comoros coelacanth population. Finally, we discuss the importance and vulnerability of the population of coelacanths inhabiting the submarine slopes of the Onilahy canyon in southwest Madagascar and make recommendations for further research and conservation.
45
Stewart, Robert, Karoly Németh, and Shane Cronin. "Is Efate (Vanuatu, SW Pacific) a result of subaerial or submarine eruption? An alternative model for the 1 Ma Efate Pumice Formation." Open Geosciences 2, no. 3 (January 1, 2010). http://dx.doi.org/10.2478/v10085-010-0020-9.
Full textAbstract:
AbstractThe Efate Pumice Formation (EPF) is a trachydacitic volcaniclastic succession widespread in the central part of Efate Island and also present on Hat and Lelepa islands to the north. The volcanic succession has been inferred to result from a major, entirely subaqueous explosive event north of Efate Island. The accumulated pumice-rich units were previously interpreted to be subaqueous pyroclastic density current deposits on the basis of their bedding, componentry and stratigraphic characteristics. Here we suggest an alternative eruptive scenario for this widespread succession. The major part of the EPF is distributed in central Efate, where pumiceous pyroclastic rock units several hundred meters thick are found within fault scarp cliffs elevated about 800 m above sea level. The basal 200 m of the pumiceous succession is composed of massive to weakly bedded pumiceous lapilli units, each 2-3 m thick. This succession is interbedded with wavy, undulatory and dune bedded pumiceous ash and fine lapilli units with characteristics of co-ignimbrite surges and ground surges. The presence of the surge beds implies that the intervening units comprise a subaerial ignimbrite-dominated succession. There are no sedimentary indicators in the basal units examined that are consistent with water-supported transportation and/or deposition. The subaerial ignimbrite sequence of the EPF is overlain by a shallow marine volcaniclastic Rentanbau Tuffs. The EPF is topped by reef limestone, which presumably preserved the underlying EPF from erosion. We here propose that the EPF was formed by a combination of initial subaerial ignimbrite-forming eruptions, followed by caldera subsidence. The upper volcaniclastic successions in our model represent intra-caldera pumiceous volcaniclastic deposits accumulated in a shallow marine environment in the resultant caldera. The present day elevated position of the succession is a result of a combination of possible caldera resurgence and ongoing arc-related uplift in the region.