scholarly journals A Confidence-Based Assessment Method for Distinguishing Pyroclastic Density Current Deposits From Other Volcaniclastic Units

2020 ◽  
Vol 8 ◽  
Author(s):  
James Cowlyn ◽  
Ben M. Kennedy ◽  
Darren M. Gravley ◽  
Shane J. Cronin

Pyroclastic density currents (PDCs) are a destructive volcanic hazard. Quantifying the types, frequency and magnitudes of PDC events is essential for effective risk management, but since historical records at best extend a few hundred years this usually relies on identifying deposits in the geological record. However, small volume unconsolidated PDC deposits have low preservation potential and can be difficult to distinguish from other volcaniclastic units, especially in proximal locations. Consequently many small or poorly exposed deposits can be overlooked. Here, we introduce a structured field method for assessing volcaniclastic deposits of unknown origin with a particular focus on identifying deposits from concentrated PDCs (pyroclastic flows). The method differs from traditional identification schemes in that it does not uniquely attribute a deposit to a single depositional process, but instead assesses how confidently different volcaniclastic processes could explain the observed deposit features. Therefore, the underlying uncertainties in the assessment are explicitly addressed. The method allows consistent, rapid assessment of candidate pyroclastic flow deposits in the field, and the concept could easily be adapted for assessing other types of volcaniclastic deposit. The introduction of confidence levels in deposit interpretations should be useful for carrying though uncertainties into probabilistic assessments of volcanic hazards.

2018 ◽  
Vol 34 (3) ◽  
pp. 633-645
Author(s):  
Cornel Samoilă ◽  
Doru Ursuţiu ◽  
Vlad Jinga

Abstract MOOC appearance has produced, in a first phase, more discussions than contributions. Despite pessimistic opinions or those catastrophic foreseeing the end of the classic education by accepting MOOC, the authors consider that, as it is happening in all situations when a field is reformed, instead of criticism or catastrophic predictions, an assessment should be simply made. MOOC will not be better or worse if it is discussed and dissected but can be tested in action, perfected by results, or abandoned if it has no prospects. Without testing, no decision is valid. A similarity between the MOOC appearance and the appearance of the idea of flying machines heavier than air can be made. In the flight case, the first reaction was a strong negation (including at Academies level) and only performing the first independent flight with an apparatus heavier than air has shifted orientation from denial to contributions. So, practical tests clarified the battle between ideas. The authors of this article encourage the idea of testing–assessment and, therefore, imagined and proposed one software for quickly assess whether MOOC produces changes in knowledge, by simply transferring courses from ‘face-to-face’ environment into the virtual one. Among the methods of statistical analysis for student behavioral changes was chosen the Keppel method. It underpins the assessment method of this work being approached using both the version with one variable and also with three variables. It is intended that this attempts to pave the way for other series of rapid assessment regarding MOOC effects (using other statistical methods). We believe, that this is the only approach that can lead either to improve the system or to renunciation.


PLoS Genetics ◽  
2010 ◽  
Vol 6 (3) ◽  
pp. e1000866 ◽  
Author(s):  
Charleston W. K. Chiang ◽  
Zofia K. Z. Gajdos ◽  
Joshua M. Korn ◽  
Finny G. Kuruvilla ◽  
Johannah L. Butler ◽  
...  

2016 ◽  
Vol 8 (4) ◽  
pp. 46
Author(s):  
Abdul Hamid Mar Iman ◽  
Edlic Sathiamurthy

Attention to damage assessment is always a priority especially in cases of natural disaster. The state of Kelantan is known to be one of a few Malaysian states with noticeable natural disaster, in particular, flood. In December 2014, an extraordinary magnitude of flood – nicknamed as yellow flood – struck the state causing hundreds of million ringgit of damage to properties. The purpose of this study is to demonstrate a spatial approach to estimating property damage incurred by flood. By selecting a badly affected area, GIS was used to map geo-referenced flood-hit location in Kuala Krai, Kelantan. Flood hazard was modelled and superimposed on estimated property damage. GIS spatial technique was then employed to estimate the flood damage incurred. This study, however, did not make a complete damage assessment of the properties but rather focusing on the methodology of damage assessment to show how it can be implemented. In conclusion, GIS spatial technique can generally be used to provide flood damage rapid assessment method.


2021 ◽  
Author(s):  
Geoffrey Lerner ◽  
Susanna Jenkins ◽  
Sylvain Charbonnier ◽  
Jean-Christophe Komorowski ◽  
Peter Baxter

Pyroclastic density currents (PDCs) that escape their confining channels are among the most dangerous of volcanic hazards. These unconfined PDCs are capable of inundating inhabited areas that may be unprepared for these hazards, resulting in significant loss of life and damage to infrastructure. Despite their ability to cause serious impacts, unconfined PDCs have previously only been described for a limited number of specific case studies. Here, we carry out a broader comparative study that reviews the different types of unconfined PDCs, their deposits, dynamics and impacts, as well as the relationships between each element. Unconfined PDCs exist within a range of concentration, velocity and temperature: characteristics that are important in determining their impact. We define four end-member unconfined PDCs: 1. fast overspill flows, 2. slow overspill flows, 3. high-energy surges, and 4. low-energy detached surges (LEDS), and review characteristics and incidents of each from historical eruptions. These four end-members were all observed within the 2010 eruptive sequence of Merapi, Indonesia. We use this well-studied eruption as a case study, in particular the villages of Bakalan, 13 km south, and Bronggang 14 km south of the volcano, which were impacted by slow overspill flows and LEDS, respectively. These two unconfined PDC types are the least described from previous eruptions, but during the Merapi eruption the overspill flow resulted in building destruction and the LEDS in significant loss of life. We discuss the dynamics and deposits of these unconfined PDCs, and the resultant impacts. We then use the lessons learned from the 2010 Merapi eruption to assess some of the impacts associated with the deadly 2018 Fuego, Guatemala eruption. Satellite imagery and media images supplementing fieldwork were used to determine the presence of both overspill flows and LEDS, which resulted in the loss of hundreds of lives and the destruction of hundreds of buildings in inundated areas within 9 km of the summit. By cataloguing unconfined PDC characteristics, dynamics and impacts, we aim to highlight the importance and value of accounting for such phenomena in emergency management and planning at active volcanoes.


2021 ◽  
Vol 21 (1) ◽  
pp. 417-437
Author(s):  
Joana Medeiros ◽  
Rita Carmo ◽  
Adriano Pimentel ◽  
José Cabral Vieira ◽  
Gabriela Queiroz

Abstract. The Azores are an active volcanic region that offers exceptional conditions for nature-based tourism, one of the main axes of economic growth in the archipelago. A future volcanic eruption may have long-term consequences to this economic sector. Therefore, it is fundamental to assess its vulnerability to volcanic hazards in order to try to mitigate the associated risk. This study proposes a new approach to assessing the economic impact of explosive eruptions on the tourism sector. We considered two eruptive scenarios for Fogo volcano (São Miguel Island), the most probable (Volcanic Explosivity Index, VEI, 4 sub-Plinian eruption) and the worst-case (VEI 5 Plinian eruption), both producing tephra fallout and pyroclastic density currents. The results of numerical simulations were overlaid with tourism-related buildings and infrastructure of Vila Franca do Campo municipality to identify the elements at risk. The loss present value method was used to estimate the benefits generated by the accommodation units over 30 years for different economic scenarios. The assessment of the economic impact using 2018 indicators reveals that in a near-total-destruction scenario, the economic loss is approximately EUR 145 million (considering a 2 % discount rate). This approach can also be applied to other volcanic regions, geologic hazards and economic sectors.


2016 ◽  
Vol 22 (1) ◽  
pp. 20 ◽  
Author(s):  
Simon Albert ◽  
Alifereti Tawake ◽  
Ron Vave ◽  
Paul Fisher ◽  
Alistair Grinham

There has been a resurgence in community-based management of coral reef resources in the developing world over the last two decades. However, many of the threats to reef ecosystems are increasing at a rate beyond local knowledge acquisition. Consequently, there is a continuing need for management tools and monitoring to support community-based approaches. Using algal, fish and reef indicators we provide a rapid assessment method of herbivorous fishes in Locally Managed Marine Areas in Fiji. The algal indicator technique provided a time-integrated assessment of the process of herbivory within Locally Managed Marine Areas and could be used by untrained community members to quantify management responses. Generally, reefs with higher herbivore biomass had a diverse low biomass of algae typical of healthy reefs. Reefs with fewer herbivores had a higher biomass of turf or leathery algae typical of degraded reefs. These results show that simple ecological indicators can be a useful addition to the existing local knowledge that underpins community-based management.


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