In flight fragmentation reduces bomb size range and hazard during explosive volcanic eruptions

Area of Science:

• Volcanology
• Geophysics
• Earth and Planetary Sciences

Background:

• Explosive volcanic eruptions eject molten magma fragments (volcanic bombs).
• In-flight fragmentation of volcanic bombs influences their dispersal and hazard potential.
• The extent and drivers of bomb fragmentation during flight are not well understood.

Purpose of the Study:

• To quantify the in-flight fragmentation of volcanic bombs.
• To identify the primary mechanisms driving bomb fragmentation during aerial transit.
• To provide data for improving volcanic hazard models and interpreting eruption deposits.

Main Methods:

• Utilized high-speed and high-definition imaging of three explosive volcanic eruptions.
• Analyzed bomb trajectories and fragmentation patterns post-ejection.
• Estimated the proportion of bombs undergoing in-flight fragmentation.

Main Results:

• In-flight fragmentation affects 73% of volcanic bombs coarser than approximately 0.2 meters.
• Bomb-to-bomb collisions and aerodynamic drag are the main fragmentation drivers.
• Drag forces selectively fragment larger, faster bombs, limiting their range.

Conclusions:

• In-flight fragmentation is a significant process in explosive eruptions.
• Understanding fragmentation mechanisms improves volcanic deposit interpretation.
• Quantified fragmentation data enhance volcanic bomb hazard modeling.