New Estimate on the Spatial Distribution of the Youngest Toba Tuff Ash

ABSTRACT Here, we introduce a new estimate on the areal extent and volume of globally dispersed Youngest Toba Tuff ash by considering the decay of grain size and primary ash thickness (PAT). The areal extent of ash dispersal is modelled by interpolating the farthest sites in four directions. For this modelling, it is assumed that (i) PAT at the farthest newly identified site is equal to the maximum size of grains retrieved and (ii) the ash particles blanket the earth up to the farthest sites in a non‐discrete manner. The volume of ash‐fall is calculated using two approaches: (i) the Voronoi tessellation and (ii) a GIS‐aided mathematical calculation. When the Voronoi tessellation estimated a maximum and minimum volume of ash as 2089 and 1276 km 3 , the GIS‐aided mathematical calculation yielded 1573 and 1312 km 3 of dense‐rock equivalent, respectively. Thus, the GIS method provided a more narrower range than the Voronoi method.