TY - JOUR

T1 - Experimental insights into pyroclast‐ice heat transfer in water‐drained, low pressure cavities during subglacial explosive eruptions

AU - Woodcock, Duncan Charles

AU - Lane, Stephen John

AU - Gilbert, Jennifer Susan

N1 - An edited version of this paper was published by AGU. Copyright 2017 American Geophysical Union. Woodcock, D. C., S. J. Lane, and J. S. Gilbert (2017), Experimental insights into pyroclast-ice heat transfer in water-drained, low-pressure cavities during subglacial explosive eruptions, J. Geophys. Res. Solid Earth, 122, 5048–5063, doi:10.1002/2016JB013872.

PY - 2017/7

Y1 - 2017/7

N2 - Subglacial explosive volcanism generates hazards that result from magma-ice interaction, including large flow rate meltwater flooding and fine-grained volcanic ash. We consider eruptions where subglacial cavities produced by ice melt during eruption establish a connection to the atmosphere along the base of the ice sheet that allows accumulated meltwater to drain. The resulting reduction of pressure initiates or enhances explosive phreatomagmatic volcanism within a steam-filled cavity with pyroclast impingement on the cavity roof. Heat transfer rates to melt ice in such a system have not, to our knowledge, been assessed previously. To study this system, we take an experimental approach to gain insight into the heat transfer processes and to quantify ice melt rates. We present the results of a series of analogue laboratory experiments in which a jet of steam, air, and sand at approximately 300°C impinged on the underside of an ice block. A key finding was that as the steam to sand ratio was increased, behavior ranged from predominantly horizontal ice melting to predominantly vertical melting by a mobile slurry of sand and water. For the steam to sand ratio that matches typical steam to pyroclast ratios during subglacial phreatomagmatic eruptions at ~300°C, we observed predominantly vertical melting with upward ice melt rates of 1.5 mm s−1, which we argue is similar to that within the volcanic system. This makes pyroclast-ice heat transfer an important contributing ice melt mechanism under drained, low-pressure conditions that may precede subaerial explosive volcanism on sloping flanks of glaciated volcanoes.

AB - Subglacial explosive volcanism generates hazards that result from magma-ice interaction, including large flow rate meltwater flooding and fine-grained volcanic ash. We consider eruptions where subglacial cavities produced by ice melt during eruption establish a connection to the atmosphere along the base of the ice sheet that allows accumulated meltwater to drain. The resulting reduction of pressure initiates or enhances explosive phreatomagmatic volcanism within a steam-filled cavity with pyroclast impingement on the cavity roof. Heat transfer rates to melt ice in such a system have not, to our knowledge, been assessed previously. To study this system, we take an experimental approach to gain insight into the heat transfer processes and to quantify ice melt rates. We present the results of a series of analogue laboratory experiments in which a jet of steam, air, and sand at approximately 300°C impinged on the underside of an ice block. A key finding was that as the steam to sand ratio was increased, behavior ranged from predominantly horizontal ice melting to predominantly vertical melting by a mobile slurry of sand and water. For the steam to sand ratio that matches typical steam to pyroclast ratios during subglacial phreatomagmatic eruptions at ~300°C, we observed predominantly vertical melting with upward ice melt rates of 1.5 mm s−1, which we argue is similar to that within the volcanic system. This makes pyroclast-ice heat transfer an important contributing ice melt mechanism under drained, low-pressure conditions that may precede subaerial explosive volcanism on sloping flanks of glaciated volcanoes.

U2 - 10.1002/2016JB013872

DO - 10.1002/2016JB013872

M3 - Journal article

VL - 122

SP - 5048

EP - 5063

JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 2169-9356

IS - 7

ER -