The radius of the umbrella cloud helps characterize large explosive volcanic eruptions

Eruption source parameters (in particular erupted volume and column height) are used by volcanologists to inform volcanic hazard assessments and to classify explosive volcanic eruptions. Estimations of source parameters are associated with large uncertainties due to various factors, including complex tephra sedimentation patterns from gravitationally spreading umbrella clouds. We modify an advection-diffusion model to investigate this effect. Using this model, source parameters for the climactic phase of the 2450 BP eruption of Pululagua, Ecuador, are different with respect to previous estimates (erupted mass: 1.5-5 x 10(11) kg, umbrella cloud radius: 10-14km, plume height: 20-30km). We suggest large explosive eruptions are better classified by volume and umbrella cloud radius instead of volume or column height alone. Volume and umbrella cloud radius can be successfully estimated from deposit data using one numerical model when direct observations (e.g., satellite images) are not available. Total erupted volume and umbrella cloud radius can inform estimates of eruption characteristics and volcanic explosivity more reliably than column height or volume alone, according to simulations of the eruption of Pululagua, Ecuador, 2,450 years ago.

Automated summary

By modifying a model and studying the eruption in Pululagua, Ecuador 2,450 years ago, it was found that the umbrella cloud radius and erupted volume are more reliable parameters for estimating eruption characteristics.