共查询到16条相似文献,搜索用时 15 毫秒
1.
Pablo Samaniego Jean-Philippe Eissen Jean-Luc Le Pennec Claude Robin Minard L. Hall Patricia Mothes Deborah Chavrit Joseph Cotten 《Journal of Volcanology and Geothermal Research》2008
A petrological study of the eruptive products of El Reventador allowed us to infer the magmatic processes related to the 2002 and 2004–05 eruptions of this andesitic stratovolcano. On November 3, 2002, El Reventador experienced a highly explosive event, which was followed by emplacement of two lava flows in November–December 2002. Silica contents range from 62 to 58 wt.% SiO2 for the November 3 pyroclastic deposits to 58–56 and 54–53 wt.% SiO2 for the successive lava flows. In November 2004 eruptive activity resumed supplying four new lava flows (56–54 wt.% SiO2) between November 2004 and August 2005. 相似文献
2.
J. Zlotnicki Y. Sasai J. P. Toutain E. U. Villacorte A. Bernard Julio P. Sabit Juan M. Gordon Jr Ernesto G. Corpuz M. Harada J. T. Punongbayan H. Hase T. Nagao 《Bulletin of Volcanology》2009,71(1):29-47
Since 1572, 33 phreatic to phreatomagmatic eruptions have occurred on Taal volcano (Philippines), some of them causing several
hundred casualties. Considering the time delay between two consecutive eruptions, there is an 88% probability that Taal volcano
should have already erupted. Since 1992, several phases of seismic activity have been recorded accompanied by ground deformation,
opening of fissures, and surface activity. The volcanic activity of Taal appears to be controlled by dike injections and magma
supply, buffered by a hydrothermal system that releases fluids and heat through boiling and subsequent steaming. In early
2005, a multidisciplinary project was launched for studying the hydrothermal activity. To map the hydrothermal system, combined
surveys were carried out to investigate self-potential, total magnetic field, ground temperature and carbon dioxide soil degassing,
along with satellite thermal imaging of the Main Crater Lake. The elevated temperatures and high concentrations of carbon
dioxide, as well as electromagnetic anomalies, indicate large-scale hydrothermal degassing. This process is enhanced along
the tectonic features (e.g., crater rim and faults) of the volcano, while active fissures opened along the E–W northern flank
during the 1992–1994 seismic activity. Heat and fluids from the hydrothermal system are essentially released in the northern
part of the crater, which is bounded to the South by a suspected NW–SE fault along which seismicity seems to take place, and
dikes are thought to be intruded. During the January 2005 surveys, a new seismic crisis started, and the felt earthquakes
prompted spontaneous evacuation of hundreds of inhabitants living on the volcano. Repeated surveys show changes of self-potential,
total magnetic field, and ground temperature with time, without any noticeable spatial enlargement. These observations suggest
that the northern flank located between the crater rim and the 1992–1994 fissures is connected with a deep thermal source
in Main crater and is reactivated during seismic crises. This sector could be subjected to flank failure. 相似文献
3.
Phreatic eruptions occurred at the Meakandake volcano in 1988, 1996, 1998, 2006, and 2008. We conducted geochemical surveillance
that included measurements of temperature, SO2 emission rates, and volcanic gas composition from 2003 to 2008 at the Nakamachineshiri (NM), Northwest (NW), and Akanuma
(AK) fumarolic areas, and the 96–1 vent, where historical eruptions had occurred. The elemental compositions of the gases
discharged from the different areas are similar compared with the large variations observed in volcanic gases discharged from
subduction zones. All the gases showed high apparent equilibrium temperatures, suggesting that all these gases originated
from a common magmatic gas. The gases discharged from each area also exhibited different characteristics, which are probably
the results of differences in the conditions of meteoric water mixing, quenching of chemical reactions, and vapor-liquid separation.
The highest apparent equilibrium temperatures (about 500°C) were observed in the case of NW fumarolic gases, despite the low
outlet temperature of about 100°C at these fumaroles. Since the NW fumaroles were formed as a result of the 2006 phreatic
eruption, the high-temperature gas supply to the NW fumarole suggests that the phreatic eruption was caused by the ascent
of high-temperature magmatic gases. The temperatures, compositions, and emission rates of the NM and 96–1 gases did not show
any appreciable change after the 2006 eruption, indicating that each fumarolic system had a separate magmatic-hydrothermal
system. The temperatures, compositions, and emission rates of the NM fumarolic gases were apparently constant, and these fumaroles
are inferred to be formed by the evaporation of a hydrothermal system with a constant temperature of about 300°C. The 96–1
gas compositions showed large changes during continuous temperature decrease from 390° to 190°C occurred from 2003 to 2008,
but the sulfur gas emission rates were almost constant at about four tons/day. At the 96–1 vent, the SO2/H2S ratio decreased, while the H2/H2O ratio remained almost constant; this was probably caused by the rock-buffer controlled chemical reaction during the temperature
decrease. 相似文献
4.
Carmelo Ferlito Marco Viccaro Eugenio Nicotra Renato Cristofolini 《Bulletin of Volcanology》2012,74(2):533-543
Mount Etna volcano (Italy) during the period 2001–2005 has undergone a period of intense eruptive activity marked by three
large eruptions (2001, 2002–2003 and 2004–2005). These eruptions encompassed diverse eruptive styles and regimes: from intensely
explosive, during 2001 and 2002–2003 eruptions, to exclusively effusive in the 2004–2005 event. In this work, we put forward
the idea that these three eruptions are the response of the progressive arrival into the uppermost segment of the open-conduit
system of a new magma, which was geochemically distinct in terms of trace element and Sr–Nd–Pb isotope signature from the
products previously emitted by the Etnean volcano. The magma migrated upwards mainly through a peripheral tectonic system,
which can be considered as eccentric in spite of its relative proximity to the main system. The ingress of the new magma and
its gradual displacement from the eccentric system into the uppermost sector of the open-conduit gave rise to different eruptive
behaviours. At the beginning, the ascent of the undegassed magma, able to exsolve a gas phase at depth, and its interaction
with closed-system magma reservoirs less than 10 km deep gave rise to the explosive events of 2001 and 2002–2003. Later, when
the same magma entered into the open-conduit system, it took part in the steady-state degassing and partially lost its volatile
load, leading to a totally effusive eruption during the 2004–2005 event. One further consideration highlighted here is that
in 2001–2005, migration of the feeding axis from an eccentric and peripheral position towards the main open-conduit has led
to the development of a new vent (South East Crater 2) located at the eastern base of the South East Crater through which
most of the subsequent Etnean activity occurred. 相似文献
5.
The emission rate of carbon dioxide escaping from the summit of Kīlauea Volcano, Hawai?i, proved highly variable, averaging 4900 ± 2000 metric tons per day (t/d) in June–July 2003 during a period of summit inflation. These results were obtained by combining over 90 measurements of COSPEC-derived SO2 emission rates with synchronous CO2/SO2 ratios of the volcanic gas plume along the summit COSPEC traverse. The results are lower than the CO2 emission rate of 8500 ± 300 t/d measured by the same method in 1995–1999 during a period of long-term summit deflation [Gerlach, T.M., McGee, K.A., Elias, T., Sutton, A.J. and Doukas, M.P., 2002. Carbon dioxide emission rate of Kīlauea Volcano: Implications for primary magma and the summit reservoir. Journal of Geophysical Research-Solid Earth, 107(B9): art. no.-2189.]. Analysis of the data indicates that the emission rates of the present study likely reflect changes in the magma supply rate and residence time in the summit reservoir. It is also likely that emission rates during the inflation period were heavily influenced by SO2 pulses emitted adjacent to the COSPEC traverse, which biased CO2/SO2 ratios towards low values that may be unrepresentative of the global summit gas plume. We conclude that the SO2 pulses are consequences of summit re-inflation under way since 2003 and that CO2 emission rates remain comparable to, but more variable than, those measured prior to re-inflation. 相似文献
6.
The Suizhou meteorite is a heavily shocked and melted vein-containing L6 chondrite. It contains a minor amount of diopside with a(Ca0.419Mg0.466Fe0.088)SiO3 composition, and a shock-metamorphosed diopside grain associated with ringwoodite and lingunite was found in a melt vein of this meteorite. Our electron microprobe,transmission electron microscopic and Raman spectroscopic analyses revealed four silicate phases with different compositions and struct... 相似文献
7.
Salvatore Alparone Graziella Barberi Alessandro Bonforte Vincenza Maiolino Andrea Ursino 《Bulletin of Volcanology》2011,73(7):869-885
We carried out a study of the seismicity and ground deformation occurring on Mt. Etna volcano after the end of the 2002–2003
eruption and before the onset of the 2004–2005 eruption. Data were recorded by the permanent local seismic network run by
Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania and by geodetic surveys carried out in July 2003 and July 2004 on the GPS network. Most earthquakes were grouped in two main
clusters located in the northeastern and southeastern sectors of the volcano. The areal distribution of seismic energy associated
with the recorded earthquakes allowed us to highlight the main seismogenic areas of Mt. Etna. In order to better understand
the kinematic processes of the volcano, 3D seismic locations were used to compute fault plane solutions, and a selected dataset
was inverted to determine stress and strain tensors. The focal mechanisms in the northeastern sector show clear left-lateral
kinematics along an E-W fault plane, consistent with events occurring along the Pernicana Fault system. The fault plane solutions
in the southeastern sector show mainly right-lateral kinematics along a NNE and ENE fault plane and left lateral-kinematics
along NW fault planes that together suggest roughly E-W oriented compression. Surface ground deformation affecting Mt. Etna
measured by GPS surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of
its eastern flank. The 2D geodetic strain tensor distribution was calculated and the results show mainly ENE-WSW extension
coupled with WNW-ESE contraction, indicating right-lateral shear along a NW-SE oriented fault plane. The different deformation
of the eastern sector of the volcano, as measured by seismicity and ground deformation, must be interpreted by considering
the different depths of the two signals. Seismic activity in the southeastern sector of volcano is located between 3 and 8 km b.s.l.
and can be associated with a very strong additional E-W compression induced by a pressurizing source just westwards and at
the same depth, located by inverting GPS data. Ground deformation, in contrast, is mainly affected by the shallower dynamics
of the fast moving eastern flank which produces a shallower opposing E-W extension. The entire dataset shows that two different
processes affect the eastern flank at the same time but at different depths; the boundary is clearly located at a depth of
3 km b.s.l. and could represent the décollement surface for the mobile flank. 相似文献
8.
The aim of this study is the refinement of the dynamics of a recent (1994?C1999) minor, slow-inflation episode of the Santorini (Thera) volcano, famous for the Minoan (??3600 B.C.) eruption and the identification of the parameters of the magmatic source responsible for the inflation. Based on the Mogi source equations, on geodetic observations of base-line changes, on a topological, grid-search approach and on the reasonable assumption that the magma source remained practically stable in map view during the inflation period, we have been able to refine the location and depth (approximately 2.7 km) of the magma center. A tendency for increase of the magma pressure with time, roughly corresponding to a sphere with radius between 30 and 60 m, and a short deflation interval were also documented. The overall modeling was based on a topological method of inversion in two steps and for a selected 4-D grid. At a first step the system of Mogi-source equations was approximated by the intersection of the 4-D subspaces (defined by sets of grid points) each satisfying one observation equation on the basis of a grid-search procedure. At a second step, the best estimate of the Mogi source solution and its full variance-covariance matrix were defined using a common stochastic approach. The overall approach leads to a solution of a system of equations focusing on a 4-D space bounding significant minima in the misfits between model and observed values, and not on solutions focusing on single points, usually trapped in local minima. This study is important to understand a new phase of volcanic unrest since January 2011, while the proposed methodology, inspired from traditional navigation methods may be useful for other inversion problems leading to redundant systems of highly non-linear equations with n unknowns (i.e. topological solutions in the n-D space). 相似文献
9.
IntroductionA large earthquake occurred in Jiji (Chi-Chi) town of Nantou County, Taiwan, China at 17h47min on September 20, 1999 (UTC). The origin time was determined to be 17h47min19s of September 20 UTC (1h47min19s of September 21, Beijing Time). The epicenter was determined to be longitude 120.80°E and latitude 23.86°N. It was reported that 2 333 people were killed, 10 002 people were injured, and thousands of houses collapsed which made more than 100 000 people homeless (Shin, e… 相似文献
10.
The air–sea ice CO2 flux was measured over landfast sea ice in the Chukchi Sea, off Barrow, Alaska in late May 2008 with a chamber technique. The ice cover transitioned from a cold early spring to a warm late spring state, with an increase in air temperature and incipient surface melt. During melt, brine salinity and brine dissolved inorganic carbon concentration (DIC) decreased from 67.3 to 18.7 and 3977.6 to 1163.5 μmol kg−1, respectively. In contrast, the salinity and DIC of under-ice water at depths of 3 and 5 m below the ice surface remained almost constant with average values of 32.4±0.3 (standard deviation) and 2163.1±16.8 μmol kg−1, respectively. The air–sea ice CO2 flux decreased from +0.7 to −1.0 mmol m−2 day−1 (where a positive value indicates CO2 being released to the atmosphere from the ice surface). During this early to late spring transition, brought on by surface melt, sea ice shifted from a source to a sink for atmospheric CO2, with a rapid decrease of brine DIC likely associated with a decrease in the partial pressure of CO2 of brine from a supersaturated to an undersaturated state compared to the atmosphere. Formation of superimposed ice coincident with melt was not sufficient to shut down ice–air gas exchange. 相似文献
11.
Ruifang HUANG Weidong SUN Xing DING Yusheng ZHAO Yibing LI Xiuqi SHANG 《中国科学:地球科学(英文版)》2024,(1):222-233
Hydrothermal alteration of olivine greatly influences geodynamics and the recycling of volatiles (such as water and carbon) in subduction zones.Silica is an important component of geological fluids,and its influence on the hydrothermal alteration of olivine remains poorly constrained.In this study,we performed experiments at 300–515℃ and 3.0 kbar (1 bar=105Pa) by reacting well homogenized mixtures of olivine and silica powders with saline solutions (0.5 mol L-1Na Cl).Silica... 相似文献
12.
Sotnikov N. V. Antonova E. E. Ryazantseva M. O. Barinova V. O. Rubinshtein I. A. Mit’ S. K. 《Geomagnetism and Aeronomy》2019,59(2):136-146
Geomagnetism and Aeronomy - This paper studies the position of the trapping boundary of electrons with energies of >100 keV relative to the equatorial boundary of the auroral oval during a... 相似文献
13.
14.
Gianfranco Di Vincenzo Laura Bracciali Paola Del Carlo Kurt Panter Sergio Rocchi 《Bulletin of Volcanology》2010,72(4):487-505
The AND-2A drillcore (Antarctic Drilling Program—ANDRILL) was successfully completed in late 2007 on the Antarctic continental
margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations
and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore
were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar–39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment
deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar–39Ar ages, indicating that the AND-2A drillcore recovered ≤230 m of Middle Miocene (∼128–358 m below sea floor, ∼11.5–16.0 Ma)
and >780 m of Early Miocene (∼358–1093 m below sea floor, ∼16.0–20.1 Ma). Results also highlight a nearly continuous stratigraphic
record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ∼19 cm/ka, possible oscillations
of no more than a few hundreds of ka and a break within ∼17.5–18.1 Ma. Comparison with available data from volcanic deposits
on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer
to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the “proto-Mount Morning” as the
main source. 相似文献
15.
Due to anthropogenic activities, the nutrient loadings of the Changjiang (Yangtze River) are strickly on the rise. The high nutrient concentrations notwithstanding, river water was pCO2 supersaturated in the inner estuary during summer 2003 but decreased quickly in the mid-estuary due to mixing with low pCO2 waters from offshore. In addition, settling of particles in the estuary resulted in better light conditions so that phytoplankton bloomed, driving down pCO2 to ∼200 μatm. In the outer estuary and outside of the bloom area, pCO2 increased again to near or just below saturation. Literature data also reveal that the mainstream of the Changjiang is always supersaturated with respect to CO2 probably because the decomposition of terrestrial organic matter overwhelms the consumption of CO2 due to biological production. 相似文献
16.