Linking lava morphologies to effusion rates for the 2014–2015 Holuhraun lava flow field, Iceland

Joana R.C Voigt,Gregor Steinbrügge,Ingibjörg Jónsdottir,Ármann Höskuldsson,Christopher W Hamilton,Thorvaldur Thordarson

doi:10.1130/g49251.1

Joana R.C Voigt, Gregor Steinbrügge + Show 4 more

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https://doi.org/10.1130/g49251.1

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Abstract

AbstractDetermining the parameters that control fissure-fed lava morphologies is critical for reconstructing the complex emplacement histories of eruptions on Earth and other planetary bodies. We used a geomorphological map of the 2014–2015 Holuhraun lava flow field, in combination with new constraints on lava emplacement chronology and two independently derived time-averaged discharge rate (TADR) data sets, to analyze correlations between lava morphology and effusion rate. Results show that lava morphologies are dominantly controlled by effusion rate at the vent during the early phases of the eruption and by lava transport processes as the system evolves. Initially, TADR and its variance, which reflect pulsation in the lava supply rate from the vent, directly affect lava emplacement styles. However, as the eruption progresses, the lava transport system exerts a stronger control with channels and ponds that can either dampen variation in local effusion rate or create surges during sudden drainage events. The Holuhraun eruption predominantly produced rubbly lava in its earlier eruption phases and transitioned into the production of spiny lava toward the end of the eruption. However, a drop of TADR during the first phase of the eruption correlates with a decrease in rubbly lava formation and an increase in spiny lava production. This suggests that a change in effusion rate caused the observed transition in lava type. Our findings show that rubbly lava is formed under relatively high local effusion rates with pulsating supply conditions, whereas spiny lava is formed under lower local effusion rates and steadier supply.

Highlights

In the case of variations in the local effusion rate, due to changes in the lava transport system, such as the development of the lava pond, which can cause a sudden surge in lava flux within a newly formed pathway, the showing breaching event at Holuhraun lava flow field, Iceland
Analysis of the lava morphology combined with the chronological emplacement of lava units and time-averaged discharge rate (TADR) for the 2014–2015 Holuhraun eruption in Iceland demonstrates a strong correlation between TADR and the final lava products
Our findings indicate that it is most likely not just the TADR, but rather the local effusion rate that exerts the dominant control on the morphologies of transitional lava types

Summary

Introduction

Linking lava morphologies to physicalparameters is key for understanding how post emplacement characteristics can be used to reconstruct eruption conditions on Earth and other planetary bodies—especially where lava flow fields record a complex history of initial flow emplacement followed by processes of dis ruption and inflation.Many parameters have been suggested as controls for lava morphologies (see the Supplemental Material1), but, generally, mor phologies are affected by a combination of the initial chemical and thermophysical properties of the lava (Macdonald, 1953; Williams and McBirney, 1979) and dynamic processes, such as volumetric flow rate and shear strain rate (Rowland and Walker, 1990; Jurado-Chichay and Rowland, 1995), which in turn depend pri marily on flow thickness and viscosity, local slope, gravitational acceleration, and the exter nal environment (Glaze et al, 2014). We created a novel chronological map of the flow growth for the 2014–2015 Holuhraun lava flow field in Iceland, and investigated relationships between time-av erage discharge rates (TADRs; Coppola et al, 2017; Bonny et al, 2018) and observed lava morphologies, or facies (Voigt et al, 2021).

Results

Conclusion