Abstract
Investigation of the ashfall deposit from the 1980 Mount St Helens eruption reveals that the deposit is bimodal, the finer population maintaining a uniform grain size distribution away from source, and that the deposit exhibits secondary thickening beyond the 1-cm isopach. Grain size distribution shows that at least 64% of the deposit is finer than 63 µm, far more than is generally supposed for plinian eruptions. An investigation of other ashfall deposits reveals similar grain size bimodality features, which are interpreted as evidence of aggregation of fine particles in the eruption cloud. Our data suggest that aggregation may be a common process during ash fallout from explosive eruptions and that secondary thickening may often occur, providing that other conditions are met.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Izett, G. A. J. geophys. Res. 86, 10200–10223 (1981).
Sparks, R. S. J. & Walker, G. P. L. J. Volcan. Geotherm. Res. 2, 329–341 (1977).
Sparks, R. S. J. & Huang, T. C. Geol. Mag. 117, 425–436 (1980).
Self, S. & Sparks, R. S. J. Bull. volcan. 41, 196–212 (1978).
Walker, G. P. L. Nature 281, p. 642–646 (1979).
Waitt, R. B. & Dzurisin, D. U.S. geol. Surv. Prof. Pap. 1250, 601–617 (1981).
Sarna-Wojcicki, A. M., Shipley, S., Waitt, R. B., Dzurisin, D. & Wood, S. H. U.S. geol. Surv. Prof. Pap. 1250, 577–601 (1981).
Carey, S. N. & Sigurdsson, H. J. geophys. Res. (in the press).
Larrson, W. Bull. geol. Inst., Upsala, 26, 27–52 (1936).
Muerdter, D., Dauphin, J. P. & Steele, G. J. sedim. Petrol. 51, 647–650 (1981).
Christiansen, R. L. & Peterson, D. W. U.S. geol. Surv. Prof. Pap. 1250, 17–30 (1981).
Sorem, R. K. J. Volcan. Geotherm. Res. 13, 63–71 (1982).
Shepherd, J. B. et al. Nature 282, 24–28 (1979).
Shepherd, J. B. & Sigurdsson, H. J. Volcan. Geotherm. Res. 13, 119–130 (1982).
Brazier, S. A., Davis, A. N., Sigurdsson, H. & Sparks, R. S. J. J. Volcan. Geotherm. Res. (in the press).
Westgate, J. A. & Evans, M. E. Can. J. Earth Sci. 15, 1554–1567 (1978).
Porter, S. C. Quat. Res. 10, 30–41 (1978).
Powers, H. A. & Wilcox, R. E. Science 144, 1334–1336 (1964).
Lerbekmo, J. F., Westgate, J., Smith, D. G. W. & Denton, G. H. Quat. Studies 203–209 (1975).
Nasmith, H., Mathews, W. H. & Rouse, G. E. Can. J. Earth Sci. 4, 163–170 (1967).
Mullineaux, D. R., Hyde, J. H. & Rubin, M. J. Res. U.S. geol. Surv. 3, 329–335 (1975).
Cornell, W., Carey, S. & Sigurdsson, H. J. Volcan. Geotherm. Res. (in the press).
Walker, G. P. L. J. Volcan. Geotherm. Res. 8, 69–94 (1980).
Carey, S. N. & Sigurdsson, H. J. Volcan. Geotherm. Res. 7, 67–86 (1980).
Machida, H. & Arai, F. Kagaku 46, 339–347 (1976).
Walker, G. P. L. Contr. Miner. Petrol. 36, 135–146 (1972).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Brazier, S., Sparks, R., Carey, S. et al. Bimodal grain size distribution and secondary thickening in air-fall ash layers. Nature 301, 115–119 (1983). https://doi.org/10.1038/301115a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/301115a0
- Springer Nature Limited
This article is cited by
-
Aerodynamic characteristics and genesis of aggregates at Sakurajima Volcano, Japan
Scientific Reports (2022)
-
Understanding and modeling tephra transport: lessons learned from the 18 May 1980 eruption of Mount St. Helens
Bulletin of Volcanology (2022)
-
Sedimentation process of ashfall during a Vulcanian eruption as revealed by high-temporal-resolution grain size analysis and high-speed camera imaging
Progress in Earth and Planetary Science (2020)
-
The 1914 Taisho eruption of Sakurajima volcano: stratigraphy and dynamics of the largest explosive event in Japan during the twentieth century
Bulletin of Volcanology (2017)
-
Ash production and dispersal from sustained low-intensity Mono-Inyo eruptions
Bulletin of Volcanology (2016)