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1.
During the 2018 eruption of Kīlauea Volcano, Hawai'i, scientists relied heavily on a conceptual model of explosive eruptions triggered when lava-lake levels drop below the water table. Numerical modeling of multiphase groundwater flow and heat transport revealed that, contrary to expectations, liquid water inflow to the drained magma conduit would likely be delayed by months to years, owing to the inability of liquid water to transit a zone of very hot rock. The summit of Kīlauea subsequently experienced an ∼2-month period of consistent repeated collapses, and the crater now extends below the equilibrium position of the water table. Liquid water first emerged into the deepened crater in late July 2019. The timing of first appearance of liquid water (about 14 months postcollapse) and the rate of crater lake filling (currently ∼27 kg/s) were well-predicted by the numerical modeling done in late spring 2018, which forecast liquid inflow after 3 to 24 months at rates of 10 to 100 kg/s. A second-generation groundwater model, reflecting the current crater geometry, forecasts lake filling over the next several years. The successful 2018 to present forecasts with both models are based on unadjusted in situ permeability estimates (1 to 6 × 10−14 m2) and water-table elevations (600 to 800 m) from a nearby research drillhole and geophysical surveys. Important unknowns that affect the reliability of longer-term forecasts include the equilibrium water-table geometry, the rate of evaporation from the hot and growing crater lake (currently ∼29,000 m2 at 70-80 °C), and heterogenous permeability changes caused by the 2018 collapse. 相似文献
2.
David A. Clague Jonathan T. Hagstrum Duane E. Champion Melvin H. Beeson 《Bulletin of Volcanology》1999,61(6):363-381
The tube-fed pāhoehoe lava flows covering much of the northeast flank of Kīlauea Volcano are named the 'Ailā'au flows. Their
eruption age, based on published and six new radiocarbon dates, is approximately AD 1445. The flows have distinctive paleomagnetic
directions with steep inclinations (40°–50°) and easterly declinations (0°–10°E). The lava was transported ∼40 km from the
vent to the coast in long, large-diameter lava tubes; the longest tube (Kazumura Cave) reaches from near the summit to within
several kilometers of the coast near Kaloli Point. The estimated volume of the 'Ailā'au flow field is 5.2±0.8 km3, and the eruption that formed it probably lasted for approximately 50 years. Summit overflows from Kīlauea may have been
nearly continuous between approximately AD 1290 and 1470, during which time a series of shields formed at and around the summit.
The 'Ailā'au shield was either the youngest or the next to youngest in this series of shields. Site-mean paleomagnetic directions
for lava flows underlying the 'Ailā'au flows form only six groups. These older pāhoehoe flows range in age from 2750 to <18,000
BP, and the region was inundated by lava flows only three times in the past 5000 years. The known intervals between eruptive
events average ∼1600 years and range from ∼1250 years to >2200 years. Lava flows from most of these summit eruptions also
reached the coast, but none appears as extensive as the 'Ailā'au flow field. The chemistry of the melts erupted during each
of these summit overflow events is remarkably similar, averaging approximately 6.3 wt.% MgO near the coast and 6.8 wt.% MgO
near the summit. The present-day caldera probably formed more recently than the eruption that formed the 'Ailā'au flows (estimated
termination ca. AD 1470). The earliest explosive eruptions that formed the Keanakāko'i Ash, which is stratigraphically above
the 'Ailā'au flows, cannot be older than this age.
Received: 10 October 1998 / Accepted: 12 May 1999 相似文献
3.
C. C. Heliker M. T. Mangan T. N. Mattox J. P. Kauahikaua R. T. Helz 《Bulletin of Volcanology》1998,59(6):381-393
The Pu'u 'Ō'ō-Kūpaianaha eruption on the east rift zone of Kīlauea began in January 1983. The first 9 years of the eruption
were divided between the Pu'u 'Ō'ō (1983–1986) and Kūpaianaha (1986–1992) vents, each characterized by regular, predictable
patterns of activity that endured for years. In 1990 a series of pauses in the activity disturbed the equilibrium of the eruption,
and in 1991, the output from Kūpaianaha steadily declined and a short-lived fissure eruption broke out between Kūpaianaha
and Pu'u 'Ō'ō. In February 1992 the Kūpaianaha vent died, and, 10 days later, eruptive episode 50 began as a fissure opened
on the uprift flank of the Pu'u 'Ō'ō cone. For the next year, the eruption was marked by instability as more vents opened
on the flank of the cone and the activity was repeatedly interrupted by brief pauses in magma supply to the vents. Episodes
50–53 constructed a lava shield 60 m high and 1.3 km in diameter against the steep slope of the Pu'u 'Ō'ō cone. By 1993 the
shield was pockmarked by collapse pits as vents and lava tubes downcut as much as 29 m through the thick deposit of scoria
and spatter that veneered the cone. As the vents progressively lowered, the level of the Pu'u 'Ō'ō pond also dropped, demonstrating
the hydraulic connection between the two. The downcutting helped to undermine the prominent Pu'u 'Ō'ō cone, which has diminished
in size both by collapse, as a large pit crater formed over the conduit, and by burial of its flanks. Intervals of eruptive
instability, such as that of 1991–1993, accelerate lateral expansion of the subaerial flow field both by producing widely
spaced vents and by promoting surface flow activity as lava tubes collapse and become blocked during pauses.
Received: 1 July 1997 / Accepted: 23 October 1997 相似文献
4.
Eruption dynamics of Hawaiian-style fountains: the case study of episode 1 of the Kīlauea Iki 1959 eruption 总被引:1,自引:1,他引:0
Wendy K. Stovall B. F. Houghton H. Gonnermann S. A. Fagents D. A. Swanson 《Bulletin of Volcanology》2011,73(5):511-529
Hawaiian eruptions are characterized by fountains of gas and ejecta, sustained for hours to days that reach tens to hundreds
of meters in height. Quantitative analysis of the pyroclastic products from the 1959 eruption of Kīlauea Iki, Kīlauea volcano,
Hawai‘i, provides insights into the processes occurring during typical Hawaiian fountaining activity. This short-lived but
powerful eruption contained 17 fountaining episodes and produced a cone and tephra blanket as well as a lava lake that interacted
with the vent and fountain during all but the first episode of the eruption, the focus of this paper. Microtextural analysis
of Hawaiian fountaining products from this opening episode is used to infer vesiculation processes within the fountain and
shallow conduit. Vesicle number densities for all clasts are high (106–107 cm−3). Post-fragmentation expansion of bubbles within the thermally-insulated fountain overprints the pre-fragmentation bubble
populations, leading to a reduction in vesicle number density and increase in mean vesicle size. However, early quenched rims
of some clasts, with vesicle number densities approaching 107 cm−3, are probably a valid approximation to magma conditions near fragmentation. The extent of clast evolution from low vesicle-to-melt
ratio and corresponding high vesicle number density to higher vesicle-to-melt ratio and lower vesicle-number density corresponds
to the length of residence time within the fountain. 相似文献
5.
Effusion rate is a primary measurement used to judge the expected advance rate, length, and hazard potential of lava flows.
At basaltic volcanoes, the rapid draining of lava stored in rootless shields and perched ponds can produce lava flows with
much higher local effusion rates and advance velocities than would be expected based on the effusion rate at the vent. For
several months in 2007–2008, lava stored in a series of perched ponds and rootless shields on Kīlauea Volcano, Hawai'i, was
released episodically to produce fast-moving 'a'ā lava flows. Several of these lava flows approached Royal Gardens subdivision
and threatened the safety of remaining residents. Using time-lapse image measurements, we show that the initial time-averaged
discharge rate for one collapse-triggered lava flow was approximately eight times greater than the effusion rate at the vent.
Though short-lived, the collapse-triggered 'a'ā lava flows had average advance rates approximately 45 times greater than that
of the pāhoehoe flow field from which they were sourced. The high advance rates of the collapse-triggered lava flows demonstrates
that recognition of lava accumulating in ponds and shields, which may be stored in a cryptic manner, is vital for accurately
assessing short-term hazards at basaltic volcanoes. 相似文献
6.
7.
8.
Observations of the summit eruption of Klyuchevskoi volcano in the period from February 15, 2007 to July 9, 2007 are considered. This typical (for this volcano) summit eruption was explosive-effusive in character. The ejectamenta volume is estimated at 0.025 km3. Calculation of active phases of the volcano was carried out in accordance with V.A. Shirokov’s technique. The identified active phases agree well with the eruptive periods. The 2007 summit eruption corresponds to an active phase (May 2006 to May 2009) favorable for the volcano’s eruption. Geodetic observations carried out since 1979 along a radial profile have revealed uplifts and subsidences of the northeastern slope of the volcano. The maximum displacement of 23 cm was recorded in 2007 on the site closest to the volcano crater at a distance of 11 km from the summit crater center. In the course of two previous summit eruptions (2003–2004 and 2005) insignificant uplifts and subsidences of the slope were also noted, although the general ascent of the slope remained. This indicated possible repeated eruptions in the nearest future. Changes in the seismicity before, during and after the eruption are also discussed. 相似文献
9.
Matthew R. Patrick Tim Orr David Wilson David Dow Richard Freeman 《Bulletin of Volcanology》2011,73(6):639-653
In late 2007, a perched lava channel, built up to 45 m above the preexisting surface, developed during the ongoing eruption
near Pu‘u ‘Ō‘ō cone on Kīlauea Volcano’s east rift zone. The lava channel was segmented into four pools extending over a total
of 1.4 km. From late October to mid-December, a cyclic behavior, consisting of steady lava level rise terminated by vigorous
spattering and an abrupt drop in lava level, was commonly observed in pool 1. We use geologic observations, video, time-lapse
camera images, and seismicity to characterize and understand this cyclic behavior. Spattering episodes occurred at intervals
of 40–100 min during peak activity and involved small (5–10-m-high) fountains limited to the margins of the pool. Most spattering
episodes had fountains which migrated downchannel. Each spattering episode was associated with a rapid lava level drop of
about 1 m, which was concurrent with a conspicuous cigar-shaped tremor burst with peak frequencies of 4–5 Hz. We interpret
this cyclic behavior to be gas pistoning, and this is the first documented instance of gas pistoning in lava well away from
the deeper conduit. Our observations and data indicate that the gas pistoning was driven by gas accumulation beneath the visco-elastic
component of the surface crust, contrary to other studies which attribute similar behavior to the periodic rise of gas slugs.
The gas piston events typically had a gas mass of about 2,500 kg (similar to the explosions at Stromboli), with gas accumulation
and release rates of about 1.1 and 5.7 kg s−1, respectively. The time-averaged gas output rate of the gas pistoning events accounted for about 1–2% of the total gas output
rate of the east rift zone eruption. 相似文献
10.
Matthew Patrick David Wilson David Fee Tim Orr Don Swanson 《Bulletin of Volcanology》2011,73(9):1179-1186
The first eruptive activity at Kīlauea Volcano’s summit in 25 years began in March 2008 with the opening of a 35-m-wide vent
in Halema‘uma‘u crater. The new activity has produced prominent very-long-period (VLP) signals corresponding with two new
behaviors: episodic tremor bursts and small explosive events, both of which represent degassing events from the top of the
lava column. Previous work has shown that VLP seismicity has long been present at Kīlauea’s summit, and is sourced approximately
1 km below Halema‘uma‘u. By integrating video observations, infrasound and seismic data, we show that the onset of the large
VLP signals occurs within several seconds of the onset of the degassing events. This timing indicates that the VLP is caused
by forces—sourced at or very near the lava free surface due to degassing—transmitted down the magma column and coupling to
the surrounding rock at 1 km depth. 相似文献
11.
12.
Servando De la Cruz-Reyna Izumi Yokoyama Alicia Martínez-Bringas Esteban Ramos 《Bulletin of Volcanology》2008,70(6):753-767
Popocatépetl Volcano is located in the central Mexican Volcanic Belt, within a densely populated region inhabited by over
20 million people. The eruptive history of this volcano indicates that it is capable of producing a wide range of eruptions,
including Plinian events. After nearly 70 years of quiescence, Popocatépetl reawakened in December 21, 1994. The eruptive
activity has continued up until the date of this submission and has been characterized by a succession of lava dome growth-and-destruction
episodes, similar to events that have apparently been typical for Popocatépetl since the fourteenth century. In this regime,
the episodes of effusive and moderately explosive activity alternate with long periods of almost total quiescence. In this
paper we analyze five years of volcano-tectonic seismicity preceding the initial eruption of the current episode. The evolution
of the V-T seismicity shows four distinct stages, which we interpret in terms of the internal processes which precede an eruption
after a long period of quiescence. The thermal effects of a magma intrusion at depth, the fracturing related to the slow development
of magma-related fluid pathways, the concentration of stress causing a protracted acceleration of this process, and a final
relaxation or redistribution of the stress shortly before the initial eruption are reflected in the rates of V-T seismic energy
release. A hindsight analysis of this activity shows that the acceleration of the seismicity in the third stage asymptotically
forecast the time of the eruption. The total seismic energy release needed to produce an eruption after a long period of quiescence
is related to the volume of rock that must be fractured so imposing a characteristic threshold limit for polygenetic volcanoes,
limit that was reached by Popocatépetl before the eruption. 相似文献
13.
Tim R. Orr 《Bulletin of Volcanology》2011,73(3):335-346
Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava
tubes. They are typified by an upraised rim of blocky rubble and a central depression. Prior to this study, shatter rings
had not been observed forming, and, thus, were interpreted in many ways. This paper describes the process of formation for
shatter rings observed at Kīlauea Volcano during November 2005–July 2006. During this period, tilt data, time-lapse images,
and field observations showed that episodic tilt changes at the nearby Pu‘u ‘Ō‘ō cone, the shallow magmatic source reservoir,
were directly related to fluctuations in the level of lava in the active lava tube, with periods of deflation at Pu‘u ‘Ō‘ō
correlating with increases in the level of the lava stream surface. Increases in lava level are interpreted as increases in
lava flux, and were coincident with lava breakouts from shatter rings constructed over the lava tube. The repetitive behavior
of the lava flux changes, inferred from the nearly continuous tilt oscillations, suggests that shatter rings form from the
repeated rise and fall of a portion of a lava tube roof. The locations of shatter rings along the active lava tube suggest
that they form where there is an abrupt decrease in flow velocity through the tube, e.g., large increase in tube width, abrupt
decrease in tube slope, and (or) sudden change in tube direction. To conserve volume, this necessitates an abrupt increase
in lava stream depth and causes over-pressurization of the tube. More than a hundred shatter rings have been identified on
volcanoes on Hawai‘i and Maui, and dozens have been reported from basaltic lava fields in Iceland, Australia, Italy, Samoa,
and the mainland United States. A quick study of other basaltic lava fields worldwide, using freely available satellite imagery,
suggests that they might be even more common than previously thought. If so, this confirms that episodic fluctuation in lava
effusion rate is a relatively common process at basaltic volcanoes, and that the presence of shatter rings in prehistoric
lava flow fields can be used as evidence that such fluctuations have occurred. 相似文献
14.
Systematic measurements of the height of the summit crater rim on the active Karymskii Volcano showed that the variation of that parameter has been greater during its last eruption, lasting, with short intermissions, from January 1, 1996 until now (October 2007) compared with the earlier eruptions. The periodic increases in the height of Karymskii Volcano were due to explosion discharges of unconsolidated pyroclastic material, with most of this falling on the volcano’s cone. The increased seismicity of Karymskii Volcano intensified the slope movement processes, resulting in a comparatively flat area forming periodically on the crater rim; during separate, not very long, periods the height of the volcanic cone was increasing in discrete steps and at a greater rate. The periodic decrease in the height of Karymskii Volcano is due to compaction of pyroclastic material and, to a much greater extent, after violent explosions which expand the crater by removing its nearsummit circumference. The other contributing factor consists in sagging of the magma column due to partial emptying of the peripheral magma chamber, which makes the internal crater slope steeper, hence causes cone collapse and the cone lower. These occurrences are generally similar to the processes of crater and caldera generation described by previous investigators for other volcanoes of the world. 相似文献
15.
David A. Clague Alice S. Davis James L. Bischoff Jacqueline E. Dixon Renee Geyer 《Bulletin of Volcanology》2000,61(7):437-449
Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted
on Lō'ihi Seamount and along the submarine east rift zone of Kīlauea Volcano. The limu o Pele fragments are undegassed with
respect to H2O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths
by cooling-contraction granulation. The limu o Pele fragments from Lō'ihi Seamount are dominantly tholeiitic basalt containing
6.25–7.25% MgO. None of the limu o Pele samples from Lō'ihi Seamount contains less than 5.57% MgO, suggesting that higher
viscosity magmas do not form lava bubbles. The dissolved CO2 and H2O contents of 7 of the limu o Pele fragments indicate eruption at 1200±300 m depth (120±30 bar). These pressures exceed that
generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing
conditions, at pressures as great as 120 bar.
Received: 22 December 1998 / Accepted: 16 July 1999 相似文献
16.
Tephra dispersed during the Millennium eruption (ME), Changbaishan Volcano, NE China provides one of the key stratigraphic links between Asia and Greenland for the synchronization of palaeoenvironmental records. However, controversy surrounds proximal-distal tephra correlations because (a) the proposed proximal correlatives of the distal ME tephra (i.e. B–Tm) lack an unequivocal chronostratigraphic context, and (b) the ME tephra deposits have not been chemically characterized for a full spectrum of element using grain-specific techniques. Here we present grain-specific glass chemistry, including for the first time, single grain trace element data, for a composite proximal sequence and a distal tephra from Lake Kushu, northern Japan (ca. 1100 km away from Changbaishan). We demonstrate a robust proximal-distal correlation and that the Kushu tephra is chemically associated with the ME/B–Tm. We propose that three of the proximal pyroclastic fall units were erupted as part of the ME. The radiocarbon chronology of the Kushu sedimentary record has been utilised to generate a Bayesian age-depth model, providing an age for the Kushu tephra which is consistent with high resolution ages determined for the eruption and therefore supports our geochemical correlation. Two further Bayesian age-depth models were independently constructed each incorporating one of two ice-core derived ages for the B–Tm tephra, providing Bayesian modelled ages of 933–949 and 944–947 cal AD (95.4%) for the Kushu tephra. The high resolution ice-core tephra ages imported into the deposition models help test and ultimately constrain the radiocarbon chronology in this interval of the Lake Kushu sedimentary record. The observed geochemical diversity between proximal and distal ME tephra deposits clearly evidences the interaction of two compositionally distinct magma batches during this caldera forming eruption. 相似文献
17.
Shinji Ohsawa Kenji Sugimori Hiroshi Yamauchi Tomoyuki Koeda Hiroaki Inaba Yoshihisa Kataoka Tsuneomi Kagiyama 《Bulletin of Volcanology》2014,76(5):1-10
A drastic change in lake water color from blue-green to brown was observed in the summit crater lake of Mt. Shinmoe-dake, Kirishima Volcano about 8 months after its 2008 eruption. The color change lasted for about 2 months (April–June 2009). The discoloration was attributed to a brownish color suspension that had formed in the lake water. X-ray fluorescence and Fourier transform infrared analyses of a sample of the suspension identified schwertmannite (Fe8O8(OH)6(SO4)). A cultivation test of iron-oxidizing bacteria for the sampled lake water with lakebed sediment revealed that the crater lake hosts iron-oxidizing bacteria, which likely participated in schwertmannite formation. We suggest that pyrite (FeS2) provided an energy source for the iron-oxidizing bacteria since the mineral was identified in hydrothermally altered tephra ejected by the August 2008 eruption. From consideration of these and other factors, the brownish discoloration of the summit crater lake of Mt. Shinmoe-dake was inferred to have resulted from a combined volcanic–microbial process. 相似文献
18.
19.
Wendy K. Stovall B. F. Houghton A. J. L. Harris D. A. Swanson 《Bulletin of Volcanology》2009,71(3):313-318
Lava lakes are found at basaltic volcanoes on Earth and other planetary bodies. Density-driven crustal foundering leading
to surface renewal occurs repeatedly throughout the life of a lava lake. This process has been observed and described in a
qualitative sense, but due to dangerous conditions, no data has been acquired to evaluate the densities of the units involved.
Kīlauea Iki pit crater in Hawai`i houses a lava lake erupted during a 2 month period in 1959. Part of the surface of the Kīlauea
Iki lake now preserves the frozen record of a final, incomplete, crustal-overturn cycle. We mapped this region and sampled
portions of the foundering crust, as well as overriding and underlying lava, to constrain the density of the units involved
in the overturn process. Overturn is driven by the advance of a flow front of fresh, low-density lava over an older, higher
density surface crust. The advance of the front causes the older crust to break up, founder, and dive downwards into the lake
to expose new, hot, low-density lava. We find density differences of 200 to 740 kg/m3 between the foundering crust and over-riding and under-lying lava respectively. In this case, crustal overturn is driven
by large density differences between the foundering and resurfacing units. These differences lead, inevitably, to frequent
crustal renewal: simple density differences between the surface crust and underlying lake lava make the upper layers of the
lake highly unstable.
Work originally presented at the American Geophysical Union Fall Meeting in San Francisco, California on December 11, 2007. 相似文献
20.
The Nevado Sabancaya in southern Peru has exhibited a persistent eruptive activity over eight years following a violent eruption in May–June 1990. The explosive activity consisted of alternated vulcanian and phreatomagmatic events, followed by declining phreatic activity since late 1997. The mean production rate of magma has remained low (106–107 m3 per year).The 1990–1998 eruptive episode produced andesitic and dacitic magmas. The juvenile tephra span a narrow range of compositions (60–64 wt% SiO2). While SiO2 contents do vary slightly, they do not show any systematic variation with time. Phenocryst assemblages in the juvenile rocks consist of mainly plagioclase, associated with high-Ca pyroxene, hornblende, biotite, and iron-titanium oxides. Rare fine-grained magmatic enclaves, with angular to subrounded shapes, are contained within some of the juvenile lava blocks, which were expelled since 1992. They have a homogeneous andesitic composition (57 wt% SiO2) and show randomly oriented interlocking columnar or acicular crystals (plagioclase and amphibole), with interstitial glass and a few voids, which define a quench-textured groundmass.Textural, mineralogical and chemical evidence suggests that the 1990–1998 eruptions have mainly erupted hybrid andesites, except for the 1990 dacite. The hybrid andesites contain a mixed population of plagioclase phenocrysts: Ca-rich clear plagioclase (An40–60), Na-rich clear plagioclase (An25–35), and inversely zoned dusty-rimmed plagioclase with a sodic core (An25–40) surrounded by a Ca-rich mantle (An45–65). Melt-inclusions, wavy dissolution surfaces and stepped zoning within the dusty-rimmed plagioclases are compatible with resorption induced by magma recharge events. Chemical and isotopic lines of evidence also show that andesites are hybrids resulting from magma mixing processes. Repeated magma recharge, incomplete homogenisation and different degrees of crustal assimilation may explain the extended range of isotopic signatures.Our study leads to propose an evolution model for the magmatic system at Nevado Sabancaya. The main magma body consisted of dacitic magmas differentiating through extensive open-system crystallization (AFC). Repeated recharge of more mafic magmas induced magma mixing, leading to the formation of hybrid andesites. A partially crystalline boundary layer formed at the interface between the andesites and the recharge magma. The magmatic enclaves were produced by the disruption and dispersion of this andesitic layer as a result of new magma injection and/or sustained tectonic activity.Periodic magma recharge and interactions with groundwater are two processes that have enabled the explosive regime to remain persistent over an 8-year-long period. What precise mechanism triggers the eruptive activity remains speculative, but it may be related either to new magma injection, or to the sustained tectonic activity that occurred at that time in the vicinity of the volcano, or a combination of both. 相似文献