Dynamics of volcanic ash remobilisation by wind through the Patagonian steppe after the eruption of Cordón Caulle, 2011

Abstract

Wind erosion of freshly-deposited volcanic ash causes persistent storms, strongly affecting ecosystems and human activity. Wind erosion of the volcanic ash was measured up to 17 months after the ash deposition, at 7 sites located within the ash-deposition area. The mass flux was measured up to 1.5 m above ground level. Mass transport rates were over 125 times the soil wind-erosion rates observed before the ash deposition, reaching up to 6.3 kg m−1 day−1. Total mass transport of ash during the 17 months ranged between 113.6 and 969.9 kg m−1 depending on topographic location and wind exposure. The vertical distribution of the mass flux at sites with higher vegetation cover was generally inverted as compared to sites with lower vegetation cover. This situation lasted 7 months and then a shift towards a more uniform vertical distribution was observed, in coincidence with the beginning of the decline of the mass transport rates. Decay rates differed between sites. Despite changes over time, an inverse linear correlation between the mass transports and the mass-flux gradients was found. Both the mass-flux gradients and the average mass-transport rates were not linked with shear-stress partition parameters, but with the ratio: ash-fall thickness to total vegetation cover.

Sources of uncertainty in the Mazama isopachs and the implications for interpreting distal tephra deposits from large magnitude eruptions

“…The modal grain size of the distal Mazama tephra (Fig. 5) falls within the range measured for resuspended modern ash in Iceland and Argentina (Liu et al 2014;Panebianco et al 2017) and is also similar to (windtransported) loess (Sun et al 2004). Semi-desert and tundra environments, which we infer a substantial proportion of the tephra was deposited in (Fig.…”

The interpretative value of transformed tephra sequences

“…This phase of reworking may persist for as long as the tephra remains on the surface and can last for years to decades, particularly in parts of the world where vegetation cover is limited, such as Iceland (Liu et al, 2014) and elsewhere, e.g. in Patagonia (Panebianco et al, 2017). Once tephra has been buried, forming a tephra layer, subsurface processes such as cryoturbation, solifluction and bioturbation can affect the tephra (Table 1).…”

Mapping Areas of the Southern Ocean Where Productivity Likely Depends on Dust‐Delivered Iron

“…Although our study does not quantify dust deposition, we assume that deposition of dust rich in bioavailable iron occurs along the transport pathway. Moreover, because we focus on select, major dust sources, we do not account for other potential vectors of airborne bioavailable iron such as volcanic ash (e.g., Duggen et al, 2007;Panebianco et al, 2017;Crespi-Abril et al, 2018) sourced from large but usually infrequent volcanic eruptions and combustion aerosols (e.g., Ito, 2015) or for emissions from cultivated land (Tegen & Fung, 1995;Tegen et al, 2004).…”