scholarly journals The summer 2019 basaltic Vulcanian eruptions (paroxysms) of Stromboli

2020 ◽  
Vol 83 (1) ◽  
Author(s):  
G. Giordano ◽  
G. De Astis
Keyword(s):  
Time Scales ◽  
Pyroclastic Flows ◽  
Level System ◽  
Subsequent Evolution ◽  
Strombolian Activity ◽  
Effusive Activity ◽  
Convective Region ◽  
Operational Time ◽  
Fall Deposits ◽  
Visual Observations

AbstractStromboli is an active, open conduit mafic volcano, whose persistent mild Strombolian activity is occasionally punctuated by much stronger explosions, known as paroxysms. During summer 2019, the volcano unexpectedly produced one such paroxysm on July 3, followed by intense explosive and intermittent effusive activity culminating in a second paroxysm on August 28. Visual observations and the analysis of the fall deposits associated with the two paroxysms allowed us to reconstruct ballistic exit velocities of up to 160 m s−1. Plume heights of ~ 8.4 km and 6.4 km estimated for the two events correspond to mass eruption rates of 1.1 × 106 kg s−1 and 3.6 × 105 kg s−1, respectively. This is certainly an underestimate as directional pyroclastic flows into which mass was partitioned immediately formed, triggering small tsunamis at the sea entrance. The mass of ballistic spatters and blocks erupted during the July 3 event formed a continuous cover at the summit of the volcano, with a mass calculated at ~ 1.4 × 108 kg. The distribution of fall deposits of both the July 3 and August 28 events suggests that pyroclasts characterized by terminal fall velocities < 10–20 m s−1 remained fully suspended within the convective region of the plume and did not fall at distances closer than ca 1700 m to the vent. Based on the impulsive, blast-like phenomenology of paroxysms as well as the deposit distribution and type, paroxysms are classified as basaltic Vulcanian in style. The evolution of the summer 2019 eruptive events was not properly captured within the framework of the alert level system which is focused on tsunamigenic processes, and this is discussed so as to provide elements for the implementation of the reference scenarios and an upgrade of the system to take into account such events. In particular we find that, although still largely unpredictable, at least at operational time scales, and not necessarily tsunamigenic, Vulcanian eruptions and the subsequent evolution of the eruptive phenomena should be considered for the alert level system. This serves as a warning to the implementation of alert systems where the unexpected needs to be taken into account, even at systems that are believed to be relatively “predictable” as is the case at many persistently active, open vent mafic systems.

Relations entre dynamismes éruptifs et réalimentations magmatiques d'origine profonde au Popocatépetl

1988 ◽  
Vol 25 (7) ◽  
pp. 955-971 ◽  
Author(s):  
Christian Boudal ◽  
Claude Robin
Keyword(s):  
Volcanic Activity ◽  
Magma Mixing ◽  
Basaltic Magma ◽  
Lava Flows ◽  
Pyroclastic Flows ◽  
Explosive Activity ◽  
Mixing Processes ◽  
Effusive Activity ◽  
Fall Deposits

The modern volcano Popocatépetl is 30 000 – 50 000 years old. Until 5000 years BP, its volcanic activity led to the construction of a 2000 m high cone, the El Fraile volcano. This edifice was later topped by the Popocatépetl summit. The volcanic activity was characterized by long-term construction by lava flows, alternating with periods of 1000–2000 years of mixed explosive and effusive activity. The El Fraile volcano experienced three periods of this type, marked by back-falling pyroclastic flows with heterogeneous magma products and thick air-fall deposits (ash and scoria). The first one occurred more than 10 000 years BP; the second, between 10 000 and 8000 years BP; the third, from 5000 to 3800 years BP. Each of these periods showed violent explosive episodes alternating with lava flows in cycles of 100 to several hundreds of years in duration. Whenever the explosive activity occurred, it destroyed the upper part of the volcano, opening large craters. After a ~ 2500 year period of lava-flow construction (from ~ 3800 to 1200 years BP), the Popocatépetl summit began a similar activity. The last event, producing pyroclastic flows, occurred just before me Hispanic Conquest, and since that time the activity has been effusive and Plinian.Heterogeneous to subhomogeneous pyroclastic flow products exhibit a complex mineralogy: Fe clinopyroxene, Mg clinopyroxene, Fe orthopyroxene, Mg orthopyroxene, plagioclase in equilibrium or disequilibrium, and scarce olivine. All lava flows show a similar paragenesis, suggesting magma-mixing processes. A model in which a basaltic magma is periodically injected in a differentiated chamber at the beginning of each explosive period (or each cycle?) is proposed to explain the heterogeneous products. However, calculations of mixing models do not agree with the high Mg and Ni values observed in some hybrid lavas. This excess is probably due to the remobilization of cumulative olivine by basic magma supplies in the lower part of the reservoir. On the other hand, lava flows emitted during the long phases of effusive activity correspond to evolution in a closed and zoned chamber, partly affected by convective movements. The convection explains the complex mineralogy of these lavas, which result from differentiation of a previously homogenized magma rather than directly from magma mixing.

The long-term evolution of the main asteroidal belt and the origin of large Mars- and Earth-crossers

1999 ◽  
Vol 173 ◽  
pp. 321-323
Author(s):  
D. Nesvorný ◽  
A. Morbidelli
Keyword(s):  
Numerical Simulations ◽  
Time Scales ◽  
Main Belt ◽  
Subsequent Evolution ◽  
Chaotic Process ◽  
The Earth ◽  
Term Evolution ◽  
Asteroidal Belt ◽  
Near Earth Asteroids

AbstractResults of numerical simulations show that the orbits of asteroids in the inner part of the main belt may gradually, subject to a chaotic process acting on 10-100 Myr time scales, become more elliptic and start intersecting the orbit of Mars. The subsequent evolution of an asteroid having close encounters with Mars frequently leads to the Earth-crossing orbit. This revolutionary scenario of the origin of near-Earth asteroids was quantified by Miglioriniet al.(1998) and here we discuss some of the aspects of this work.

The transitions from mildly explosive to caldera-forming eruptions at Colli Albani volcano (Italy)

2021 ◽  
Author(s):  
Mónica Ágreda López ◽  
Luca Caricchi ◽  
Corin Jorgenson ◽  
Alessandro Musu ◽  
Guido Giordano
Keyword(s):  
Mineral Chemistry ◽  
Supervised Machine Learning ◽  
Learning Approaches ◽  
Magmatic System ◽  
Effusive Activity ◽  
Wide Range ◽  
Colli Albani ◽  
Petrology And Geochemistry ◽  
Similarities And Differences ◽  
Fall Deposits

&lt;p&gt;The Colli Albani volcano is an ultrapotassic caldera complex located 30 km to the SE of Rome and has displayed a wide range of eruptive behaviors, ranging from effusive activity to highly explosive and large volume eruptions (up to 63 km&lt;sup&gt;3&lt;/sup&gt; dense rock equivalent per eruption) despite its mafic nature.&lt;/p&gt;&lt;p&gt;We combine physical volcanology, petrology, and geochemistry to focus on the mildly explosive to effusive products of two sections (Tuscolo and Artemisio) which are located on opposite sides of the main caldera and stratigraphically between the last large ignimbrite, Villa Senni. The target of this study is to identify the processes responsible for the transition from the smaller explosions to the larger caldera-forming ignimbrite eruptions, and eventually trace how the magmatic system rebuilds in the interim.&lt;/p&gt;&lt;p&gt;Whole rock analyses, mineral chemistry, and petrography of fall deposits from both field localities are compared with an existing dataset for the Villa Senni ignimbrites. We will use unsupervised and supervised machine learning approaches to identify similarities and differences between large caldera-forming eruptions and mild-explosive to effusive activity and identify the processes modulating the transition between these two behaviours.&lt;/p&gt;

Monitoring of Merapi volcano, Indonesia based on Sentinel-1 data

2021 ◽  
Author(s):  
Virginie Pinel ◽  
François Beauducel ◽  
Raditya Putra ◽  
Sulis Sulistiyani ◽  
Gusti Made Agung Nandaka ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Displacement ◽  
Field Measurements ◽  
Summit Crater ◽  
Radar Data ◽  
Pyroclastic Flows ◽  
Mean Velocity ◽  
Merapi Volcano ◽  
Synthetic Aperture Radar Data ◽  
Effusive Activity

&lt;p&gt;Despite the well-established interest of Synthetic Aperture Radar data for volcanoes study and monitoring, their integration to operational monitoring activities in volcanoes observatories remains limited so far. We here describe the effort in progress to integrate in near real time the information derived from Sentinel-1 satellites into the monitoring devices at BBPTKG in charge of Merapi volcano survey as well as the use of Sentinel-1 data during the recent period of &amp;#160;unrest. Merapi (7&amp;#176;32.5&amp;#8217; S and 110&amp;#176;26.5&amp;#8217; E) located in the densely populated Province of Yogyakarta in Central Java is one of the most active volcanoes in Indonesia. The eruptive history of Merapi is characterized by two eruptive styles: 1) recurrent effusive growth of viscous lava domes, with gravitational collapses producing pyroclastic flows known as &amp;#171; Merapi-type nu&amp;#233;es ardentes &amp;#187; (VEI 2); 2) more exceptional explosive eruptions of relatively large size (VEI 3-4), associated with column collapse pyroclastic flows reaching distances larger than 15 km from the summit. The eruptive periodicity is 4 to 5 years for the effusive events and 50 to 100 years for the explosive ones. The last explosive events (VEI 3-4) occurred in November 2010 and was followed by a period of limited activity. In August 2018, a new dome was observed inside the summit crater, thus marking the start of a new phase of effusive activity. A new period of unrest then started in mid-October 2020, characterized by an increase in seismic activity as well as large and localized displacements in the summit area. Magma finally reached the surface on 4&lt;sup&gt; &amp;#160;&lt;/sup&gt;January 2021. Deformation is currently recorded by EDM and tiltmeters together with a network of 10 permanent GNSS stations. GNSS data are automatically processed and inverted for a pressure source at depth. Both displacement time series as well as spatial probability distribution are directly available through WebObs (Beauducel et al., Frontiers, 2020), an integrated web-based system for monitoring. Sentinel-1 data are acquired over the volcano every 12 days on descending track 76 and every 6 days on ascending track 127. Since mid 2017, Sentinel-1 data are automatically downloaded on a local server at BPPTKG. Interferograms and coherence images are then produced using the NSBAS processing chain (Doin et al, 2012) and automatically integrated to WebObs to enable detection of potential rapid and significant changes in signal. Mean velocity maps are also produced as well as time series of surface displacement at given location enabling direct comparison with GNSS measurements. The descending InSAR time series shows a strong displacement away from the satellite in a 1.5 km wide area located on the north-eastern part &amp;#160;of the crater. This signal became significant in September 2020. It is consistent with field measurements recorded and allows to map the affected area. In mid-November 2020, Sentinel-1 data thus provided the first information on the spatial extent of the ongoing surface displacements, which was useful for crisis management.&lt;/p&gt;

scholarly journals Ground Deformation Detected by Permanent Tiltmeters on Mt. Etna Summit: The August 23-26, 2018, Strombolian and Effusive Activity Case

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Salvatore Gambino ◽  
Marco Aloisi ◽  
Giuseppe Di Grazia ◽  
Giuseppe Falzone ◽  
Angelo Ferro ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Volcanic Tremor ◽  
Mount Etna ◽  
Etna Volcano ◽  
Strombolian Activity ◽  
Summit Area ◽  
Effusive Activity ◽  
Ground Deformations ◽  
Mt Etna ◽  
Set Up

Over the last few years, three tilt deep stations (27-30 meters) have been set up in the summit area of Mount Etna volcano. The aim of this challenging project is to record the ground deformations of the summit craters activity with high precision. We considered data related to the August 23-26, 2018, Strombolian and effusive activity. In this case, tiltmeters recorded variations in the order of 10−7 radians, not observed at the other stations. These changes suggest a shallow contraction source just south of the Southeast Crater. This result, related to the volcanic tremor source, points to the presence of a gas/magma reservoir feeding the Strombolian activity at 1200 m above sea level.

Stratigraphy, chronology, styles and dynamics of late Quaternary eruptions from Taupo volcano, New Zealand

1993 ◽  
Vol 343 (1668) ◽  
pp. 205-306 ◽  
Keyword(s):  
New Zealand ◽  
Fractal Dimensionality ◽  
Pyroclastic Flows ◽  
Taupo Volcanic Zone ◽  
Caldera Collapse ◽  
Volcanic Zone ◽  
Oruanui Eruption ◽  
Self Similar ◽  
Taupo Volcano ◽  
Fall Deposits

Taupo volcano is the southerly of two dormant caldera volcanoes in the rhyolite-dominated central portion of the Taupo Volcanic Zone in the North Island of New Zealand. Taupo has an average magma output rate of 0.2 m 3 s -1 over the past 65 000 years, and is one of the most frequently active and productive rhyolite volcanoes known. The structure of the modern ‘inverse’ volcano was formed largely by caldera collapse associated with the voluminous 22 600 14 C years BP Oruanui eruption, and has been little modified since except for collapse following the 1850 14 C years BP eruption. The products of 28 eruptions (labelled T, f2, A, ..., Z), all of which post-date the Oruanui eruption, are defined and described here. Twenty-seven of these eruptions are represented by pyroclastic deposits (of which three were accompanied by a mappable lava extrusion), and one eruption (Z) solely by evidence for a lava extrusion. The deposits of seven eruptions (B, C, E, S, V, X and Y) largely correspond to previously defined tephra formations (Karapiti, Poronui, Opepe, Waimihia, Whakaipo, Mapara and Taupo, respectively). The previously defined Motutere and Hinemaiaia Tephras are reinterpreted to represent the products of 12 eruptions (G to R), while the remaining eight deposits and one eruption are newly recognized. Eruption T occurred at ca . 17200 14 C or 20500 calibrated years BP and eruption Z about 1740 calibrated years BP. Eruption volumes vary by more than three orders of magnitude between 0.01 and more than 44 km 3 , and repose periods by more than two orders of magnitude from ca . 20 to 6000 years. The eruption deposits reflect great variations in parameters such as volume, the dispersal characteristics of the fall deposits, the presence or absence of intraeruptive time breaks, the formation of pyroclastic flows, the degree of magmawater interaction, the vesiculation state of the magma on fragmentation and the relative proportions of juvenile obsidian versus foreign lithologies in the lithic fractions. All but seven fall deposits are plinian in dispersal; two (Y1 and probably W) are sub-plinian, one (Y5) has been termed ‘ultraplinian’, while 4/ and A are too poorly preserved for their dispersal to be assessed. The lengths of repose periods in the post-Oruanui sequence range are not randomly distributed but show self-similar properties (fractal dimensionality); repose intervals ( r , in years) of not more than 350 years follow n = 53.5r-0'21, and those of not less than 350 years follow n = 2096 r -0-83 , where n is the number of eruptions. The shorter repose periods may reflect triggering processes, such as regional extension, affecting magma bodies during their viable lifetimes, while longer repose intervals (i.e. not less than 350 years) may reflect an episodicity of major rifting events or the production of magma bodies below the volcano. Bulk volumes ( v , in km 3 ) of the eruption products also show self-similar properties (fractal dimensionality), with n = 6.17 v -0.46 . However, there are then apparently random relationships between eruption volumes and the preceding or succeeding repose period such that prediction of the time and size of the next eruption is impossible. The post-Oruanui activity at Taupo represents ‘noise’ superimposed on the more uniform, longer term activity in the central Taupo Volcanic Zone, where large (greater than 100 km 3 ) eruptions, such as the Oruanui, occur at more evenly spaced intervals of one per 40-60000 years.

scholarly journals A new infrared volcano monitoring using GCOM-C (SHIKISAI) satellite: Applications to the Asia-Pacific region

2020 ◽  
Author(s):  
Takayuki Kaneko ◽  
Atsushi Yasuda ◽  
Kenji Takasaki ◽  
Shun Nakano ◽  
Toshitsugu Fujii ◽  
...  
Keyword(s):  
Large Scale ◽  
Lava Dome ◽  
Global Climate ◽  
Thermal Anomaly ◽  
Pyroclastic Flows ◽  
Asia Pacific ◽  
Small Scale ◽  
Effusive Activity ◽  
Lake Temperature ◽  
Satellite Applications

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 μm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2-3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-μm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63- and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

Tracking the evolution of the Merapi volcano crater area by high-resolution satellite imagery

2020 ◽  
Author(s):  
Virginie Pinel ◽  
Raditya Putra ◽  
Akhmad Solikhin ◽  
François Beauducel ◽  
Agus Budi Santoso ◽  
...  
Keyword(s):  
High Resolution ◽  
Summit Crater ◽  
Pyroclastic Flows ◽  
Merapi Volcano ◽  
Effusive Activity ◽  
Large Size ◽  
Optical Images ◽  
History Of ◽  
High Resolution Satellite Imagery ◽  
The City

&lt;p&gt;Located about 30 km north of the city of Yogyakarta, Merapi is considered as one of the most dangerous volcano of Indonesia with 3000 to 5000 fatalities since 1672 and about two million people living at less than 30 km from the crater. The recent eruptive history of Merapi is characterized by two eruptive styles: 1) recurrent effusive growth of viscous lava domes, with gravitational collapses producing pyroclastic flows known as &amp;#171; Merapi-type nu&amp;#233;es ardentes &amp;#187; (VEI 2); 2) more exceptional explosive eruptions of relatively large size (VEI 3-4), associated with column collapse pyroclastic flows reaching distances larger than 15 km from the summit. The eruptive periodicity is 4 to 5 years for the effusive events and 50 to 100 years for the explosive ones. The last explosive events (VEI 3-4) occurred in November 2010 and opened a 500m wide and 250m deep crater. After the 2010 eruption, the activity has been reduced. We used TerraSAR-X data to characterize eruptive deposits emplaced during the 2010 event as well as sudden destabilization of crater walls. The activity increased significantly during the spring of 2018 when several phreatic eruptions were recorded with ash emission reaching an elevation of more than 5 kilometers. The 11&lt;sup&gt;th&lt;/sup&gt; of August 2018 a new dome was observed inside the summit crater, thus marking the start of a new phase of effusive activity. It is essential to be able to quantitatively follow the temporal evolution of the dome shape and volume through time as its potential destabilisation would produce pyroclastic flow on the volcano flank. A time series of five tri-stereo Pleiades optical images, acquired between February and September 2019, is used to produce High Resolution DEMs of Merapi summit area with a spatial resolution of 3 m and a vertical precision of 1 m. By using a DEM derived from Pleiades stereo images acquired in April 2013 as a reference, the dome volume evolution through time is estimated. We show that the dome had already reached a volume around 0.5 Mm&lt;sup&gt;3&lt;/sup&gt; (+- 0.02Mm&lt;sup&gt;3&lt;/sup&gt;) end of February 2019 corresponding to a mean effusive rate of 3000 m&lt;sup&gt;3&lt;/sup&gt;/day during 6 months and that its size remained constant after February 2019. These results are consistent with volume estimations derived from drone measurements. However DEMs derived from Pleiades images enable to monitor a larger area and reveal accumulation of eruptive deposits due to dome destabilization a few hundreds of meters below the dome. The magma effusive rate thus remained significant but was reduced to 250 m&lt;sup&gt;3&lt;/sup&gt;/day from February to September 2019.&lt;/p&gt;

scholarly journals Simultaneous effusive and explosive cinder cone eruptions at Veniaminof Volcano, Alaska

Volcanica ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 295-307
Author(s):  
Christopher Waythomas
Keyword(s):  
Cinder Cone ◽  
Strombolian Activity ◽  
Effusive Activity ◽  
Conduit System ◽  
Simultaneous Activity ◽  
Conduit Network ◽  
Flank Vents

Historical eruptions of Veniaminof Volcano, Alaska have all occurred at a 300-m-high cinder cone within the icefilled caldera that characterizes the volcano. At least six of nineteen historical eruptions involved simultaneous explosive and effusive activity from separate vents. Eruptions in 1944, 1983–1984, 1993–1994, 2013, 2018 and 2021 included periods of explosive ash-producing Strombolian activity from summit vents and simultaneous nonexplosive effusion of lava from flank vents on either the southern or northeast sides of the cone. A T-junction conduit network is proposed to explain the simultaneous eruptive styles and as a mechanism for gas-magma segregation that must occur to produce the observed activity. Historical eruptions with simultaneous summit and flank activity produced slightly higher rising ash clouds compared to historical eruptions where simultaneous activity did not occur. This could be a consequence of the partitioning of more gas-charged magma into the vertical conduit of a T-junction conduit system.

LVSEM: Past Present and Future

1990 ◽  
Vol 48 (1) ◽  
pp. 364-365
Author(s):  
James B. Pawley
Keyword(s):  
Field Emission ◽  
Line Width ◽  
Time Scales ◽  
Silicon Oxide ◽  
Beam Current ◽  
High Brightness ◽  
High Beam ◽  
Fixed Charges ◽  
Beam Voltage ◽  
Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

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