scholarly journals Sequential fragmentation/transport theory, pyroclast size–density relationships, and the emplacement dynamics of pyroclastic density currents — A case study on the Mt. St. Helens (USA) 1980 eruption

2014 ◽  
Vol 275 ◽  
pp. 1-13 ◽  
Author(s):  
Chelsea Mackaman-Lofland ◽  
Brittany D. Brand ◽  
Jacopo Taddeucci ◽  
Kenneth Wohletz
Keyword(s):  
Transport Theory ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Sequential Fragmentation

Hazards and Risks at Gunung Merapi, Central Java: A Case Study

2005 ◽  
Author(s):  
Jean-Claude Thouret ◽  
Franck Lavigne
Keyword(s):  
Pyroclastic Flows ◽  
Pyroclastic Density Currents ◽  
Hazard Map ◽  
Density Currents ◽  
Danger Zone ◽  
Merapi Volcano ◽  
Central Java ◽  
Dome Extrusion ◽  
Risk Areas

Of the 1.1 million people living on the flanks of the active Merapi volcano in Java (average population density: 1140 inhabitants per km2), 440 000 live in relatively high-risk areas prone to pyroclastic flows, surges, and lahars. The sixty-one reported eruptions since the mid-1500s killed about 7000 people. For the last two centuries the activity of Merapi has alternated regularly between long periods of lava dome extrusion and brief explosive episodes with dome collapse pyroclastic flows at eight- to fifteen-year intervals. Violent explosive episodes on an average recurrence of twenty-six to fifty-four years have generated pyroclastic flows, surges, tephra falls, and subsequent lahars. The current hazard zone map of Merapi (Pardyanto et al. 1978) portrays three areas, termed the forbidden zone, first danger zone, and second danger zone, based on progressively declining hazard intensity. Revision of the hazard map has been carried out because it lacked the details necessary to outline hazard zones with accuracy (in particular the valleys likely to be swept by lahars), and excluded some areas likely to be devastated by pyroclastic density currents, such as the 22 November 1994 surge. In addition, risk maps were developed in order to incorporate social, technical, and economic elements of vulnerability (Lavigne 1998, 2000) in the decision-making progress. Eruptive hazard assessment at Merapi is based on reconstructed eruptive history, based on eruptive behaviour and scenarios combined with existing models and preliminary numerical modelling (Thouret et al. 2000). The reconstructed past eruptive activity and related damage define the extent and frequency of pyroclastic flows, the most hazardous phenomenon (Camus et al. 2000; Newhall et al. 2000). Pyroclastic flows travelled as far as 9–15 km from the source, pyroclastic surges swept the flanks as far as 9–20 km away from the vent, thick tephra fall buried temples in the vicinity of Yogyakarta 25 km to the south, and subsequent lahars spilled down radial valleys as far as 30 km to the west and south. At least one large edifice collapse has occurred in the past 7000 years (Camus et al. 2000; Newhall et al. 2000).

scholarly journals Volcano–glacier interactions on composite cones and lahar generation: Nevado del Ruiz, Colombia, case study

2007 ◽  
Vol 45 ◽  
pp. 115-127 ◽  
Author(s):  
J.C. Thouret ◽  
J. Ramírez C. ◽  
B. Gibert-Malengreau ◽  
C.A. Vargas ◽  
J.L. Naranjo ◽  
...  
Keyword(s):  
Pyroclastic Flows ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Long Term Effects ◽  
Ice Cap ◽  
The North ◽  
Potential Source ◽  
Ice Field

AbstractThe catastrophic lahars triggered by the 13 November 1985 eruption of the ice-clad Nevado del Ruiz volcano, Colombia, demonstrate that the interaction of hot pyroclasts with snow and ice can release 30–50 millionm3 of meltwater in 30–90 minutes. The 1985 eruption caused a 16% loss in area and a 9% loss in volume of snow, firn and ice. Turbulent pyroclastic density currents mechanically mixed with snow and produced meltwater at a rate of 0.5–1.6mms–1. Laboratory experiments suggest that turbulent, fluidized pyroclastic density currents exert mechanical and thermal scour, thereby efficiently transferring heat from hot pyroclasts to snow. Ice cap loss at Nevado del Ruiz continued between 1985 and 2000, representing a ∽52% decline in area and a ∽30% fall in volume. Ice 60–190m thick caps the east and southeast summit plateau, whereas an ice field < 30m thick and devoid of snow is retreating on the north, northeast and west edges. This asymmetrical distribution of ice reflects combined long-term effects of the 1985 eruption and of the post-1985 ice cap retreat. Should volcanic activity resume, steep-sided glaciers can fail and pyroclastic flows and surges can sweep the snowpack and generate mixed avalanches and lahars. Although the potential source of meltwater has decreased since 1985, extensive debris at the ice cap margins can be incorporated to future lahars.

Pyroclastic density currents at Etna volcano, Italy: The 11 February 2014 case study

2018 ◽  
Vol 357 ◽  
pp. 92-105 ◽  
Author(s):  
Daniele Andronico ◽  
Alessio Di Roberto ◽  
Emanuela De Beni ◽  
Boris Behncke ◽  
Antonella Bertagnini ◽  
...  
Keyword(s):  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Etna Volcano

scholarly journals Scenario-Based Pyroclastic Density Current Invasion Maps at Poorly Known Volcanoes: A Case Study from Changbaishan (China/North Korea)

2020 ◽  
Vol 10 (7) ◽  
pp. 2622
Author(s):  
Anna Maria Lombardi ◽  
Pierdomenico Del Gaudio ◽  
Zhengfu Guo ◽  
Maoliang Zhang ◽  
Guoming Liu ◽  
...  
Keyword(s):  
North Korea ◽  
Density Current ◽  
Rapid Evaluation ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Eruptive History ◽  
Probability Maps ◽  
Changbaishan Volcano ◽  
Global Datasets

Changbaishan volcano (China/North Korea; last eruption in 1903 AD) was responsible for a Volcanic Explosivity Index (VEI) 7 eruption in 946 AD. Approximately 186,000 people live around Changbaishan and 2,000,000 tourists/year visit the volcano. An unrest occurred between 2002 and 2006. Despite the relevant hazard, the eruptive history is poorly known, a condition common to many volcanoes worldwide. Here, we investigate the extension of the areas potentially affected by pyroclastic density currents (PDCs) in case of future eruptions following a scenario-based approach. We perform energy cone runs referred to four scenarios from columns of height 3, 10, 20 and 30 km at different vents. By using global datasets on PDCs, we produce spatial probability maps of PDCs invasion. Empirical laws between covered areas, PDC travelled distances, and heights of collapse are provided. In scenarios 3 and 4, PDCs expand at distances up to 42 km and 85 km, respectively. In scenarios 1 and 2, PDCs invade the touristic area and few main roads. Severe effects emerge from scenarios 3 and 4 with the interruption of the China–North Korea land and aerial connections and PDC. Our approach may serve as guide for the rapid evaluation of the PDC-related hazard at poorly known volcanoes.

Experimental constraints on volcanic ash generation and clast morphometrics in pyroclastic density currents and granular flows

2021 ◽  
Author(s):  
Adrian Hornby ◽  
Ulrich Kueppers ◽  
Benedikt Maurer ◽  
Carina Poetsch ◽  
Donald Dingwell
Keyword(s):  
Experimental Approach ◽  
Direct Evidence ◽  
General Description ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Shape Factors ◽  
Material Density ◽  
Bed Height ◽  
Rotary Drum ◽  
Basal Flow

&lt;p&gt;Pyroclastic density currents (PDCs) present perhaps the greatest proximal primary hazard of volcanic activity and produce abundant fine ash that can present a range of health, environment and infrastructure hazards. However, direct, fully quantitative observation of ash production in PDCs is lacking, and little direct evidence exists to constrain the parameters controlling ash generation in PDCs. Here, we use an experimental approach to investigate the effects of starting mass, material density and ash removal on the efficiency of ash generation and concurrent clast rounding in the dense basal flow of PDCs. We employ a rotary drum to tumble pumice and scoria lapilli clasts over multiple transport &amp;#8220;distance&amp;#8221; steps (from 0.2 to 6&amp;#160;km). We observe increased ash generation rates with the periodic removal of ash during the experiments and with increasing starting mass. By scaling to the bed height and clast diameter we obtain a general description for ash production in all experiments as a function of flow distance, bed height and average clast diameter. We confirm that changes in lapilli shape factors correlate with the ash fraction generated and that the grain size of ash produced decreases with distance. Finally, we estimate shear rate in our experiments and calculate the inertial number, which describes the ratio between clast-scale and flow-scale rearrangement during flow. We show that, under certain conditions, fractional ash production can be calculated accurately for any starting mass solely as a function of the inertial number and the flow distance. This work sheds light on some of the first systematic and generalizable experimental parameterizations of ash production and associated clast evolution in PDCs and should advance our ability to understand flow mobility and associated hazards.&lt;/p&gt;

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