One-, two- and three-phase viscosity treatments for basaltic lava flows

Area of Science:

• Geophysics and Volcanology
• Rheology of complex fluids
• Materials science

Background:

• Lava flows are complex three-phase mixtures of melt, crystals, and bubbles.
• Existing models inadequately address the combined effects of crystallinity and vesicularity on lava viscosity.
• Accurate viscosity assessment is crucial for understanding lava flow dynamics and eruption hazards.

Purpose of the Study:

• To investigate the applicability of existing one- and two-phase lava viscosity models.
• To evaluate a novel three-phase model for predicting the viscosity of basaltic lava mixtures.
• To compare model predictions with field measurements from Mauna Loa and Mount Etna.

Main Methods:

• Analysis of existing one- and two-phase viscosity models for lava flows.
• Application of a three-phase mixture viscosity model incorporating melt, crystals, and bubbles.
• Case studies using lava flow data from Mauna Loa, Hawaii, and Mount Etna, Italy.

Main Results:

• The three-phase model accurately predicts measured viscosities for Etnean lava (5600-12,500 Pa s) with coexisting crystals and vesicles.
• The three-phase model successfully characterizes the full range of eruption viscosities at Mauna Loa (110-1400 Pa s).
• The model demonstrates sensitivity to variations in crystal content, bubble content, and bubble shape.

Conclusions:

• The three-phase model provides a robust framework for characterizing basaltic lava mixture viscosity.
• This approach enhances the understanding of how melt, crystals, and bubbles influence lava flow rheology.
• The validated three-phase model has significant potential for improving volcanic hazard assessment and eruption forecasting.