Publication Spotlight: Volcanic Eruptions
‘Video-based measurements of the entrainment, speed and mass flux in a wind-blown eruption column’
Paper by Dr Nicola Mingotti and Professor Andy Woods
Published May 2024
Direct observations of wind-blown volcanic plumes are limited which makes model validation difficult. However, this paper details how Andy and Nicola gained access to a high-resolution video of the May 4, 2010, Eyjafjallajökull Volcano eruption which enabled uniquely insightful analysis of the particle-laden air dynamics beneath the plume of this famous eruption.
Using advanced image processing on this footage, Andy and Nicola analysed how the plume’s horizontal speed adjusted to ambient wind and tracked changes in its radius and centre of mass over time. These observations yielded new constraints on wind-dominated plume entrainment rates, consistent with lab findings, and allowed Andy and Nicola to estimate a 43% decrease in the eruption rate over the observed 17 minutes.
Example time series image, located at a certain downwind distance in the plume. See figure 2 of the paper which displays time series comparisons.
The new contributions of this paper include:
- Direct Observational Data: This research uses high-resolution video footage of the Eyjafjallajökull Volcano eruption, examining detailed real-time dynamics of a wind-blown volcanic plume. This footage provided rare observational data on plume shape, turbulence, and particle descent speeds, which are typically challenging to obtain in field studies.
- Quantification of Horizontal Speed Adjustment: Through image processing of the footage, Andy and Nicola measured the length scale over which the horizontal speed of the plume adjusted to ambient wind speed. This measurement provides new insights into the interaction between the plume and environmental wind, which is critical for understanding plume behavior under different wind conditions.
- Analysis of Plume Radius and Center of Mass Evolution: The paper presents the evolution of the plume’s radius and center of mass over time as it moved downwind, providing quantitative data on the plume’s spatial and temporal development.
- New Constraints on Wind-Dominated Entrainment Rates: By comparing these observations with theoretical models and laboratory experiments, Andy and Nicola derived new constraints on entrainment rates in wind-dominated plumes. This contributes to improving the accuracy of models used to predict plume behavior.
- Estimation of Eruption Rate Change: Using a simplified theoretical model alongside the observational data, they estimated a 43% decrease in the eruption rate over the 17-minute sequence, offering insights into how eruption intensity can vary on short timescales.
These contributions advance our understanding of how wind influences volcanic plumes, offering more accurate data and models for future studies and improving eruption forecasting.