The Irosin co-ignimbrite ash-fall deposit: A widespread tephra marker in the Bicol arc, south Luzon, Philippines

2011 ◽  
Vol 246 (1-2) ◽  
pp. 389-395 ◽  
Author(s):  
Ma. Hannah T. Mirabueno ◽  
Mitsuru Okuno ◽  
Masayuki Torii ◽  
Tohru Danhara ◽  
Eduardo P. Laguerta ◽  
...  
Keyword(s):  
Fall Deposit ◽  
Ash Fall

Age of the Rockland tephra, western USA

2004 ◽  
Vol 62 (1) ◽  
pp. 94-104 ◽  
Author(s):  
M.A. Lanphere ◽  
D.E. Champion ◽  
M.A. Clynne ◽  
J.B. Lowenstern ◽  
A.M Sarna-Wojcicki ◽  
...  
Keyword(s):  
North America ◽  
National Park ◽  
Fall Deposit ◽  
Ion Microprobe ◽  
Western North America ◽  
Weighted Mean ◽  
Central California ◽  
Ash Fall ◽  
Lassen Peak ◽  
Eruption Age

The age of the Rockland tephra, which includes an ash-flow tuff south and west of Lassen Peak in northern California and a widespread ash-fall deposit that produced a distinct stratigraphic marker in western North America, is constrained to 565,000 to 610,000 yr by 40Ar/39Ar and U–Pb dating. 40Ar/39Ar ages on plagioclase from pumice in the Rockland have a weighted mean age of 609,000 ± 7000 yr. Isotopic ages of spots on individual zircon crystals, analyzed by the SHRIMP-RG ion microprobe, range from ∼500,000 to ∼800,000 yr; a subpopulation representing crystal rims yielded a weighted-mean age of 573,000 ± 19,000 yr. Overall stratigraphic constraints on the age are provided by two volcanic units, including the underlying tephra of the Lava Creek Tuff erupted within Yellowstone National Park that has an age of 639,000 ± 2000 yr. The basaltic andesite of Hootman Ranch stratigraphically overlies the Rockland in the Lassen Peak area and has 40Ar/39Ar ages of 565,000 ± 29,000 and 565,000 ± 12,000 yr for plagioclase and groundmass, respectively. Identification of Rockland tephra in ODP core 1018 offshore of central California is an important stratigraphic age that also constrains the eruption age to between 580,000 and 600,000 yr.

Mount Etna and the 1971 eruption - Ash deposits from the new explosion crater, Etna 1971

1973 ◽  
Vol 274 (1238) ◽  
pp. 147-151 ◽  
Keyword(s):  
Grain Size ◽  
Mount Etna ◽  
Explosion Crater ◽  
Fall Deposit ◽  
Explosive Activity ◽  
Eastern Side ◽  
Ash Fall ◽  
Grade Material ◽  
Grain Size Parameters ◽  
Pyroclastic Fall

The weakly explosive activity in May to June 1971 from the new explosion crater high on the eastern side of Etna produced a pyroclastic fall deposit which is very poorly sorted on the crater rim , but is well sorted farther away. Grain-size parameters are given for 47 sieved samples, seven of which were collected from the ash-fall during the eruption. The initial strombolian-type activity soon changed as pre-existing pyroclastic debris slid into the crater, and thereafter the ejecta included much non-juvenile material derived from this debris. The ash fell in the form of small damp flocculated clumps, but as it dried out much of the dust-grade material was blown away by the wind. Such dust may account for much of the loess-like soil found on the vegetated lower slopes of Etna.

scholarly journals A simple semi-empirical approach to model thickness of ash-deposits for different eruption scenarios

2010 ◽  
Vol 10 (11) ◽  
pp. 2241-2257 ◽  
Author(s):  
A. O. González-Mellado ◽  
S. De la Cruz-Reyna
Keyword(s):  
Active Volcano ◽  
Fall Deposit ◽  
Unknown Parameters ◽  
Graphic Interface ◽  
Deposit Thickness ◽  
Ash Fall ◽  
Accurate Perception ◽  
User Friendly ◽  
Semi Empirical ◽  
The Impact

Abstract. The impact of ash-fall on people, buildings, crops, water resources, and infrastructure depends on several factors such as the thickness of the deposits, grain size distribution and others. Preparedness against tephra falls over large regions around an active volcano requires an understanding of all processes controlling those factors, and a working model capable of predicting at least some of them. However, the complexity of tephra dispersion and sedimentation makes the search of an integral solution an almost unapproachable problem in the absence of highly efficient computing facilities due to the large number of equations and unknown parameters that control the process. An alternative attempt is made here to address the problem of modeling the thickness of ash deposits as a primary impact factor that can be easily communicated to the public and decision-makers. We develop a semi-empirical inversion model to estimate the thickness of non-compacted deposits produced by an explosive eruption around a volcano in the distance range 4–150 km from the eruptive source. The model was elaborated from the analysis of the geometric distribution of deposit thickness of 14 world-wide well-documented eruptions. The model was initially developed to depict deposits of potential eruptions of Popocatépetl and Colima volcanoes in México, but it can be applied to any volcano. It has been designed to provide planners and Civil Protection authorities of an accurate perception of the ash-fall deposit thickness that may be expected for different eruption scenarios. The model needs to be fed with a few easy-to-obtain parameters, namely, height of the eruptive column, duration of the explosive phase, and wind speed and direction, and its simplicity allows it to run in any platform, including a personal computers and even a notebook. The results may be represented as tables, two dimensional thickness-distance plots, or isopach maps using any available graphic interface. The model has been tested, with available data from some recent eruptions in México, and permits to generate ash-fall deposit scenarios from new situations, or to recreate past situations, or to superimpose scenarios from eruptions of other volcanoes. The results may be displayed as thickness vs. distance plots, or as deposit-thickness scenarios superimposed on a regional map by means of a visual computer simulator based on a user-friendly built-in computer graphic interface.

Integrated Monitoring of Volcanic Ash and Forecasting at Sakurajima Volcano, Japan

2019 ◽  
Vol 14 (5) ◽  
pp. 798-809 ◽  
Author(s):  
Masato Iguchi ◽  
Haruhisa Nakamichi ◽  
Hiroshi Tanaka ◽  
Yusaku Ohta ◽  
Atsushi Shimizu ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Ground Deformation ◽  
Discharge Rate ◽  
Seismic Energy ◽  
Deformation Monitoring ◽  
Volcanic Plume ◽  
Fall Deposit ◽  
Integrated Monitoring ◽  
Sakurajima Volcano ◽  
Ash Fall

The Sakurajima volcano is characterized by frequent vulcanian eruptions at the Minamidake or Showa crater in the summit area. We installed an integrated monitoring system for the detection of volcanic ash (composed of remote sensing sensors XMP radars, lidar, and GNSS with different wave lengths) and 13 optical disdrometers on the ground covering all directions from the crater to measure drop size distribution and falling velocity. Campaign sampling of volcanic ash supports the conversion of particle counts measured by the disdrometer to the weight of volcanic ash. Seismometers and tilt/strain sensors were used to estimate the discharge rate of volcanic ash from the vents. XMP radar can detect volcanic ash clouds even under visual difficulty because of weather such as fog or clouds. A vulcanian eruption on November 13 was the largest event at the Sakurajima volcano in 2017; however, the volcanic plume was not visible due to clouds covering the summit. Radar revealed that the volcanic plume reached an elevation of 4.2–6.2 km. Post-fit phase residuals (PPR) from the GNSS analysis increased suddenly after the eruption, and large-PPR paths from the satellites to the ground-based receivers intersected each other at an elevation of 4.2 km. The height of the volcanic plume was also estimated from the discharge rate of volcanic ash to be 4.5 km, which is empirically related to seismic energy and the deflation volume obtained via ground deformation monitoring. Using the PUFF model, the weight of the ash-fall deposit was accurately forecast in the main direction of transport of the volcanic ash, which was verified by disdrometers. For further advances in forecasting of the ash-fall deposit, we must consider high-resolution wind field, shape of volcanic plume as the initial value, and the particle number distribution along the volcanic plume.

scholarly journals Kusatsu-Shirane volcano eruption on January 23, 2018, observed using JMA operational weather radars

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Eiichi Sato
Keyword(s):  
Field Survey ◽  
Estimation Method ◽  
Volcanic Tremor ◽  
Lower Troposphere ◽  
Eruption Style ◽  
Weather Radars ◽  
Ash Fall ◽  
Self Defense ◽  
Erupted Mass ◽  
Eruption Plume

AbstractA phreatic eruption suddenly occurred at Motoshirane (Kusatsu-Shirane volcano, Japan) at 10:02 JST on January 23, 2018. A member of the Japan Self-Defense Force was killed by volcanic blocks during training in Motoshirane, and 11 people were injured by volcanic blocks or fragments of broken glass. According to a field survey, ash fall was confirmed in Minakami, about 40 km east-northeast from Motoshirane. Although the eruption was not captured by a distant camera, the eruption plume/cloud was captured by three of the Japan Meteorological Agency’s operational weather radars. These radars observed the echo propagated to the northeast in the lower troposphere, and to the east in the middle troposphere. This is generally consistent with the observed ash fall distribution. Using the modified probabilistic estimation method, the maximum plume height was estimated to be about 5580 ± 506 m (1σ) above sea level. Estimates of the erupted mass based on the range of plume heights from radar observations and the duration of volcanic tremor during the eruption (about 8 min) do not match that obtained from a field survey (3.0–5.0 × 107 kg). This discrepancy confirms that estimates of erupted mass based on plume heights must account for eruption style parametrically, which can only be constrained by case studies of varied eruption styles.

The volcanological significance of deep-sea ash layers associated with ignimbrites

1980 ◽  
Vol 117 (5) ◽  
pp. 425-436 ◽  
Author(s):  
R. S. J. Sparks ◽  
T. C. Huang
Keyword(s):  
Deep Sea ◽  
Eastern Mediterranean ◽  
Eruption Column ◽  
Size Distributions ◽  
Ash Fall ◽  
Column Collapse ◽  
Median Diameter ◽  
Grain Size Distributions ◽  
Bimodal Grain Size ◽  
Fall Deposits

SummaryMany volcanic ash layers preserved in deep-sea sediments are the products of large magnitude ignimbrite eruptions. The characteristics of such co-ignimbrite ash-fall deposits are illustrated by two layers from the Eastern Mediterranean: the Minoan ash, Santorini, and the Campanian ash, Italy. These layers are divisible into a coarse lower unit and a fine upper unit in proximal cores. Both layers also show striking bimodal grain size distributions in more distal cores. The coarser mode decreases in median diameter with distance from source whereas the finer mode shows no lateral variation. These features are interpreted in terms of a model for ignimbrite formation by eruption column collapse. Comparable volumes of ignimbrite and associated air-fall ejecta are produced.

Accounts of an Ash Fall

Science ◽  
1983 ◽  
Vol 220 (4599) ◽  
pp. 848-848
Author(s):  
R. T. HOLCOMB
Keyword(s):  
Ash Fall
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