Total grain-size distribution and volume of tephra-fall deposits

Bonadonna, Costanza; Houghton, B. F.

doi:10.1007/s00445-004-0386-2

Cited by 337 publications

(313 citation statements)

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“…Similarly, we estimate a minimum total tephra volume of 0.17 km 3 (Table 1), a mass of 1.7 Â 10 11 kg. This estimate projects the thickening rate derived from our mapped regions to the volcano location, and in reality, based on observations elsewhere [Pyle, 1989;Bonadonna and Houghton, 2005], more rapid proximal thickening is likely. For example, assuming proximal thickening to a maximum of 1 m, based on events of similar magnitude, we produce a total tephra mass of 2.4 Â 10 11 kg, using the same density for the proximal deposit as for the distal.…”

Section: Eruption Volumesmentioning

confidence: 63%

“…[8] All our isopach data can be approximated by two or three exponential segments, as commonly observed for explosive eruption deposits ( Figure 2) [Pyle, 1989;Bonadonna and Houghton, 2005]. From this we estimate that 1.6 Â 10 11 kg of ash was deposited over Argentina.…”

Section: Eruption Volumesmentioning

confidence: 70%

“…In more distal locations (>200 km from the vent), ash fallout from discrete eruptive phases may be distinguished when transported over areas without previous ashfall (e.g., 3 and 6 May; Figure 1), and is the result of multiple eruption phases over a time period sufficient to encompass changes in wind conditions. The total area enclosed by the 0.1 mm isopach is $1.7 Â 10 5 km 2 , much larger than that of the Fuego 1974 deposit ($3 Â 10 3 km 2 ) , but comparable to the 1980 Mt St Helens eruption ($3 Â 10 5 km 2 ) [Bonadonna and Houghton, 2005]. The 1 mm isopach area (2.9 Â 10 4 km 2 ) suggests that the Chaitén eruption was an order of magnitude smaller than that of Hudson, 1991 (1.1 Â 10 5 km 2 ) [Scasso et al, 1994].…”

Section: Ash Distributionmentioning

confidence: 87%

“…[12] For tephra deposits with few distal data points the extrapolation of a proximal exponential segment can produce volume underestimation [Bonadonna and Houghton, 2005], and a power law relationship may better represent the deposit:…”

Section: B04207mentioning

confidence: 99%

“…where B is defined by the maximum thickness predicted from the exponential relationship, such that B = (T 0 /T PL ) -1/m and C is the downwind distance limit of volcanic cloud spreading, assessed from satellite images [Bonadonna and Houghton, 2005].…”

Section: B04207mentioning

confidence: 99%

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Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile

et al. 2009

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[1] The major explosive eruption of Chaitén volcano, Chile, in May 2008 provided a rare opportunity to track the long-range dispersal and deposition of fine volcanic ash. The eruption followed $10,000 years of quiescence, was the largest explosive eruption globally since Hudson, Chile, in 1991, and was the first explosive rhyolitic eruption since Novarupta, Alaska, in 1912. Field examination of distal ashfall indicates that $1.6 Â 10 11 kg of ash (dense rock equivalent volume of $0.07 km 3 ) was deposited over $2 Â 10 5 km 2 of Argentina during the first week of eruption. The minimum eruption magnitude, estimated from the mass of the tephra deposit, is 4.2. Several discrete ashfall units are identifiable from their distribution and grain size characteristics, with more energetic phases showing a bimodal size distribution and evidence of cloud aggregation processes. Ash chemistry was uniform throughout the early stages of eruption and is consistent with magma storage prior to eruption at depths of 3-6 km. Deposition of ash over a continental region allowed the tracking of eruption development and demonstrates the potential complexity of tephra dispersal from a single eruption, which in this case comprised several phases over a week-long period of intense activity.

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Section: Eruption Volumesmentioning

confidence: 63%

Section: Eruption Volumesmentioning

confidence: 70%

Section: Ash Distributionmentioning

confidence: 87%

Section: B04207mentioning

confidence: 99%

Section: B04207mentioning

confidence: 99%

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Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile

et al. 2009

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Constraining particle size‐dependent plume sedimentation from the 17 June 1996 eruption of Ruapehu Volcano, New Zealand, using geophysical inversions

et al. 2014

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Weak subplinian-plinian plumes pose frequent hazards to populations and aviation, yet many key parameters of these particle-laden plumes are, to date, poorly constrained. This study recovers the particle size-dependent mass distribution along the trajectory of a well-constrained weak plume by inverting the dispersion process of tephra fallout. We use the example of the 17 June 1996 Ruapehu eruption in New Zealand and base our computations on mass per unit area tephra measurements and grain size distributions at 118 sample locations. Comparisons of particle fall times and time of sampling collection, as well as observations during the eruption, reveal that particles smaller than 250 μm likely settled as aggregates. For simplicity we assume that all of these fine particles fell as aggregates of constant size and density, whereas we assume that large particles fell as individual particles at their terminal velocity. Mass fallout along the plume trajectory follows distinct trends between larger particles (d ≥ 250 μm) and the fine population (d < 250 μm) that are likely due to the two different settling behaviors (aggregate settling versus single-particle settling). In addition, we computed the resulting particle size distribution within the weak plume along its axis and find that the particle mode shifts from an initial 1 mode to a 2.5 mode 10 km from the vent and is dominated by a 2.5 to 3 mode 10-180 km from vent, where the plume reaches the coastline and we do not have further field constraints. The computed particle distributions inside the plume provide new constraints on the mass transport processes within weak plumes and improve previous models. The distinct decay trends between single-particle settling and aggregate settling may serve as a new tool to identify particle sizes that fell as aggregates for other eruptions.

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Testing the accuracy of a 1‐D volcanic plume model in estimating mass eruption rate

Mastin

2014

JGR Atmospheres

111

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During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historical eruptions where plume height H obs was well observed and mass eruption rate M obs could be calculated from mapped deposit mass and observed duration. The simulations considered wind, temperature, and phase changes of water. Atmospheric conditions were obtained from the National Center for Atmospheric Research Reanalysis 2.5°model. Simulations calculate the minimum, maximum, and average values (M min , M max , and M avg ) that fit the plume height. Eruption rates were also estimated from the empirical formula M empir = 140H obs 4.14 (M empir is in kilogram per second, H obs is in kilometer). For these eruptions, the standard error of the residual in log space is about 0.53 for M avg and 0.50 for M empir . Thus, for this data set, the model is slightly less accurate at predicting M obs than the empirical curve.The inability of this model to improve eruption rate estimates may lie in the limited accuracy of even well-observed plume heights, inaccurate model formulation, or the fact that most eruptions examined were not highly influenced by wind. For the low, wind-blown plume of 14-18 April 2010 at Eyjafjallajökull, where an accurate plume height time series is available, modeled rates do agree better with M obs than M empir .

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Total grain-size distribution and volume of tephra-fall deposits

Cited by 337 publications

References 45 publications

Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile

Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile

Constraining particle size‐dependent plume sedimentation from the 17 June 1996 eruption of Ruapehu Volcano, New Zealand, using geophysical inversions

Testing the accuracy of a 1‐D volcanic plume model in estimating mass eruption rate

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