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Diversity of soluble salt concentrations on volcanic ash aggregates from a variety of eruption types and deposits.

Colombier, Mathieu and Mueller, Sebastian B. and Kueppers, Ulrich and Scheu, Bettina and Delmelle, Pierre and Cimarelli, Corrado and Cronin, Shane J. and Brown, Richard J. and Tost, Manuela and Dingwell, Donald B. (2019) 'Diversity of soluble salt concentrations on volcanic ash aggregates from a variety of eruption types and deposits.', Bulletin of volcanology., 81 (7). p. 39.


Ash aggregation is a common phenomenon in particle-laden environments of volcanic eruption plumes and pyroclastic density currents. Many of these initially fragile aggregates gain sufficient mechanical strength to remain intact after atmospheric transport and deposition. Several processes contribute to ash aggregate stability, including electrostatic and hydrostatic bonding, ice formation, and cementation by salt precipitates. Here, we compare leachate chemistry from aggregates from a variety of eruption and sedimentation conditions, ranging from dry magmatic eruptions with immediate deposition, to eruptions through seawater. The leachate data shows that the broad window of opportunity for aggregation and aggregate break-up may be used to qualitatively constrain suspended ash concentration and its temporal evolution. We show that aggregation rate and aggregate stability largely depend on the availability of external water and salt source. In particular, high humidity and extensive salt precipitation in seawater environments, such as during the Surtseyan eruptions, promote high aggregation rates and aggregate stability, with accordingly accentuated proximal deposition and aggregate concentration in the deposits. On the other hand, low humidity and salt concentrations during dry magmatic eruptions promote less aggregation and more efficient aggregate break-up, explaining the rarity of aggregates in the deposits. These results have strong implications for the ash budget in volcanic plumes and associated models of plume dispersal and related hazards.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Publisher statement:This is a post-peer-review, pre-copyedit version of an article published in Bulletin of volcanology. The final authenticated version is available online at:
Date accepted:31 May 2019
Date deposited:11 September 2019
Date of first online publication:17 June 2019
Date first made open access:17 June 2020

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