scholarly journals Assessing Volcanic Hazard and Exposure at Obscure Volcanic Fields: A Case Study from the Bolaven Volcanic Field, Laos

2022 ◽  
Author(s):  
Andrea Verolino
Keyword(s):  
Volcanic Hazard ◽  
Volcanic Field ◽  
Volcanic Fields

Case study and event analysis for mitigation of unpredictable volcanic hazard

Impact ◽  
2020 ◽  
Vol 2020 (3) ◽  
pp. 26-28
Author(s):  
Tsukasa Ohba
Keyword(s):  
At Risk ◽  
Graduate School ◽  
Volcanic Hazard ◽  
Hazard Mitigation ◽  
Scientific Discipline ◽  
Mitigation Measures ◽  
Event Analysis ◽  
Traditional Methods ◽  
Risk Communities

Volcanology is an extremely important scientific discipline. Shedding light on how and why volcanoes erupt, how eruptions can be predicted and their impact on humans and the environment is crucial to public safety, economies and businesses. Understanding volcanoes means eruptions can be anticipated and at-risk communities can be forewarned, enabling them to implement mitigation measures. Professor Tsukasa Ohba is a scientist based at the Graduate School of International Resource Studies, Akita University, Japan, and specialises in volcanology and petrology. Ohba and his team are focusing on volcanic phenomena including: phreatic eruptions (a steam-driven eruption driven by the heat from magma interacting with water); lahar (volcanic mudflow); and monogenetic basalt eruptions (which consist of a group of small monogenetic volcanoes, each of which erupts only once). The researchers are working to understand the mechanisms of these phenomena using Petrology. Petrology is one of the traditional methods in volcanology but has not been applied to disastrous eruptions before. The teams research will contribute to volcanic hazard mitigation.

scholarly journals Aging of basalt volcanic systems and decreasing CO<sub>2</sub> consumption by weathering

2019 ◽  
Vol 7 (1) ◽  
pp. 191-197 ◽  
Author(s):  
Janine Börker ◽  
Jens Hartmann ◽  
Gibran Romero-Mujalli ◽  
Gaojun Li
Keyword(s):  
Age Distribution ◽  
Aging Effect ◽  
Hydrothermal Activity ◽  
Volcanic Field ◽  
Critical Zone ◽  
Volcanic System ◽  
Reactive Material ◽  
Volcanic Fields ◽  
Basalt Weathering ◽  
Aging Function

Abstract. Basalt weathering is one of many relevant processes balancing the global carbon cycle via land–ocean alkalinity fluxes. The CO2 consumption by weathering can be calculated using alkalinity and is often scaled with runoff and/or temperature. Here, it is tested if the surface age distribution of a volcanic system derived by geological maps is a useful proxy for changes in alkalinity production with time. A linear relationship between temperature normalized alkalinity fluxes and the Holocene area fraction of a volcanic field was identified using information from 33 basalt volcanic fields, with an r2=0.93. This relationship is interpreted as an aging function and suggests that fluxes from Holocene areas are ∼10 times higher than those from old inactive volcanic fields. However, the cause for the decrease with time is probably a combination of effects, including a decrease in alkalinity production from material in the shallow critical zone as well as a decline in hydrothermal activity and magmatic CO2 contribution. The addition of fresh reactive material on top of the critical zone has an effect in young active volcanic settings which should be accounted for, too. A comparison with global models suggests that global alkalinity fluxes considering Holocene basalt areas are ∼60 % higher than the average from these models imply. The contribution of Holocene areas to the global basalt alkalinity fluxes is today however only ∼5 %, because identified, mapped Holocene basalt areas cover only ∼1 % of the existing basalt areas. The large trap basalt proportion on the global basalt areas today reduces the relevance of the aging effect. However, the aging effect might be a relevant process during periods of globally intensive volcanic activity, which remains to be tested.

scholarly journals Volcanic hazard and risk assessment in a multi-source volcanic area: the example of Napoli city (Southern Italy)

2011 ◽  
Vol 11 (4) ◽  
pp. 1057-1070 ◽  
Author(s):  
I. Alberico ◽  
P. Petrosino ◽  
L. Lirer
Keyword(s):  
Risk Assessment ◽  
Volcanic Hazard ◽  
Volcanic Field ◽  
Campi Flegrei ◽  
Volcanic Area ◽  
Central Volcano ◽  
Field Frequency ◽  
Future Possibility ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment

Abstract. The possible emplacement of pyroclastic fall and flow products from Campi Flegrei and Somma-Vesuvio represents a threat for the population living in Napoli city. For this area, the volcanic hazard was always partially investigated to define the hazard related to the Campi Flegrei or to the Somma-Vesuvio activity one at a time. A new volcanic hazard and risk assessment, at the municipality scale, as a vital tool for decision-making about territorial management and future planning, is presented here. In order to assess the hazard related to the explosive activity of both sources, we integrated the results of field studies and numerical simulations, to evaluate the future possibility for Napoli to be hit by the products of an explosive eruption. This is defined for the Somma Vesuvio central volcano through the sum of "field frequency" based on the thickness and distribution of past deposits (Lirer et al., 2001), and for the Campi Flegrei volcanic field by suitably processing simulated events based on numerical modelling (Alberico et al., 2002; Costa et al., 2009). Aiming at volcanic risk assessment, the hazard areas were joined with the exposure map, considered for our purposes as the economical value of artefacts exposed to hazard. We defined four risk classes, and argued that the medium and low-very low risk classes have the largest extent in Napoli municipality, whereas only few zones located in the eastern part of the city and in the westernmost coastal area show a high risk, owing to the correspondence of high economical value and high hazard.

scholarly journals Age and mantle sources of Quaternary basalts associated with “leaky” transform faults of the migrating Anatolia-Arabia-Africa triple junction

Geosphere ◽  
2020 ◽  
Author(s):  
Michael A. Cosca ◽  
Mary Reid ◽  
Jonathan R. Delph ◽  
Gençalioğlu Kuşcu Gonca ◽  
Janne Blichert-Toft ◽  
...  
Keyword(s):  
Partial Melting ◽  
Fault Zone ◽  
Triple Junction ◽  
Lithospheric Mantle ◽  
Seismic Imaging ◽  
Plate Boundary ◽  
Volcanic Field ◽  
Plate Boundaries ◽  
Transform Faults ◽  
Volcanic Fields

The Anatolia (Eurasia), Arabia, and Africa tec­tonic plates intersect in southeast Turkey, near the Gulf of İskenderun, forming a tectonically active and unstable triple junction (the A3 triple junction). The plate boundaries are marked by broad zones of major, dominantly left-lateral transform faults including the East Anatolian fault zone (the Anato­lia-Arabia boundary) and the Dead Sea fault zone (the Arabia-Africa boundary). Quaternary basalts occur locally within these “leaky” transform fault zones (similar to those observed within oceanic transform faults), providing evidence that mantle melting, basalt genesis, and eruption are linked to crustal deformation and faulting that extends into the upper mantle. We investigated samples of alkaline basalt (including basanite) from the Toprakkale and Karasu volcanic fields within a broad zone of transtension associated with these plate-boundary faults near the İskenderun and Amik Basins, respectively. Toprakkale basalts and basanites have 40Ar/39Ar plateau ages ranging from 810 ± 60 ka to 46 ± 13 ka, and Karasu volcanic field basalts have 40Ar/39Ar plateau ages ranging from 2.63 ± 0.17 Ma to 52 ± 16 ka. Two basanite samples within the Toprak­kale volcanic field have isotopic characteristics of a depleted mantle source, with 87Sr/86Sr of 0.703070 and 0.703136, 143Nd/144Nd of 0.512931 and 0.512893, 176Hf/177Hf of 0.283019 and 0.282995, 206Pb/204Pb of 19.087 and 19.155, and 208Pb/204Pb of 38.861 and 38.915. The 176Hf/177Hf ratios of Toprakkale basalts (0.282966–0.283019) are more radiogenic than Karasu basalts (0.282837–0.282965), with some overlap in 143Nd/144Nd ratios (0.512781–0.512866 vs. 0.512648–0.512806). Toprakkale 206Pb/204Pb ratios (19.025 ± 0.001) exhibit less variation than that observed for Karasu basalts (18.800–19.324), and 208Pb/204Pb values for Toprakkale basalts (38.978– 39.103) are slightly lower than values for Karasu basalts (39.100–39.219). Melting depths estimated for the basalts from both volcanic fields gener­ally cluster between 60 and 70 km, whereas the basanites record melting depths of ~90 km. Depth estimates for the basalts largely correspond to the base of a thin lithosphere (~60 km) observed by seismic imaging. We interpret the combined radio­genic isotope data (Sr, Nd, Hf, Pb) from all alkaline basalts to reflect partial melting at the base of the lithospheric mantle. In contrast, seismic imaging indicates a much thicker (&gt;100 km) lithosphere beneath southern Anatolia, a substantial part of which is likely subducted African lithosphere. This thicker lithosphere is adjacent to the surface loca­tions of the basanites. Thus, the greater melting depths inferred for the basanites may include par­tial melt contributions either from the lithospheric mantle of the attached and subducting African (Cyprean) slab, or from partial melting of detached blocks that foundered due to convective removal of the Anatolian lithosphere and that subsequently melted at ~90 km depth within the asthenosphere. The Quaternary basalts studied here are restricted to a broad zone of transtension formed in response to the development of the A3 triple junction, with an earliest erupted age of 2.63 Ma. This indicates that the triple junction was well established by this time. While the current posi­tion of the A3 triple junction is near the Amik Basin, faults and topographic expressions indicate that inception of the triple junction began as early as 5 Ma in a position farther to the northeast of the erupted basalts. Therefore, the position of the A3 triple junction appears to have migrated to the southwest since the beginning of the Pliocene as the Anatolia-Africa plate boundary has adjusted to extrusion (tectonic escape) of the Anatolia plate. Establishment of the triple junction over the past 5 m.y. was synchronous with rollback of the Afri­can slab beneath Anatolia and associated trench retreat, consistent with Pliocene uplift in Cyprus and with the current positions of plate boundaries. The A3 triple junction is considered to be unstable and likely to continue migrating to the southwest for the foreseeable geologic future.

MULTIFRACTAL CHARACTERIZATION OF REMOTELY SENSED VOLCANIC FEATURES: A CASE STUDY FROM KILAUEA VOLCANO, HAWAII

Fractals ◽  
2002 ◽  
Vol 10 (03) ◽  
pp. 265-274 ◽  
Author(s):  
DANY C. HARVEY ◽  
HÉLÈNE GAONAC'H ◽  
SHAUN LOVEJOY ◽  
JOHN STIX ◽  
DANIEL SCHERTZER
Keyword(s):  
Thermal Infrared ◽  
Remotely Sensed ◽  
Volcanic Field ◽  
Kilauea Volcano ◽  
Statistical Characteristics ◽  
Volcanic Gas ◽  
Kīlauea Volcano ◽  
Infrared Wavelengths

We used a multifractal approach to characterize scale by scale, the remotely sensed visible and thermal-infrared volcanic field, at Kilauea Volcano, Hawaii, USA. Our results show that (1) the observed fields exhibit a scaling behavior over a resolution range of ~ 2.5 m to 6 km, (2) they show a strong multifractality, (3) the multifractal parameters α, C1 and H are sensitive to volcanic structural classes such as vent cones, lava ponds and active to inactive lava flows, (4) vegetation area and volcanic gas plumes have a strong effect on the multifractal estimates, and (5) vegetation and cloud-free images show statistical characteristics due to topography related albedo in the visible and predominantly solar heating in the thermal infrared wavelengths.

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