HR: 13:40h
AN: V13E-01 INVITED [Abstracts]
TI: The Stability of Lava Lakes
AU: * Witham, F
EM: fred.witham@bristol.ac.uk
AF: Dept Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol,
BS8 1RJ, United Kingdom
AU: * Witham, F
EM: fred.witham@bristol.ac.uk
AF: BP Institute, University of Cambridge, Cambridge, CB3 0EZ, United Kingdom
AU: Llewellin, E W
EM: ed.llewellin@durham.ac.uk
AF: Dept Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol,
BS8 1RJ, United Kingdom
AU: Llewellin, E W
EM: ed.llewellin@durham.ac.uk
AF: Dept. Earth Sciences, Durham University, Science Labs, Durham, DH1 3LE, United
Kingdom
AU: Woods, A W
EM: andy@bpi.cam.ac.uk
AF: BP Institute, University of Cambridge, Cambridge, CB3 0EZ, United Kingdom
AU: Gladstone, C
EM: lotty@bpi.cam.ac.uk
AF: BP Institute, University of Cambridge, Cambridge, CB3 0EZ, United Kingdom
AB:
Lava lakes may exhibit complex cycles of filling and draining on time-scales of hours to weeks. Such activity is
recorded at Pu`u `O`o, Hawai`i. Other examples, e.g. Erta Ale in Ethiopia, do not display these draining episodes;
instead an ‘equilibrium' system is observed in which the lake may persist for years. We present the results of a
theoretical and experimental investigation of lava lakes and identify behavioural regimes distinguished by system
geometry and gas content.
Laboratory analogue modelling shows that even a simple conduit-lake system, driven by a constant gas flux, can
display steady-state equilibrium or cyclic behaviour, depending on the rate of gas flux. A theoretical approach to
the same system captures this range of behaviour. By testing the stability of an ‘equilibrium' lake to small
perturbations, we show that the degree of stability is controlled by the ratio of conduit to lake areas, and the gas
volume fraction at the top of the conduit. Despite the simplicity of the modelled system, a rich spectrum of
behaviour is found.
The model predicts that a stable system must drain over time. This implies that lakes which exhibit ongoing
degassing for years or decades (e.g. Erta Ale) either must have an exogenous supply of gas bubbles from depth,
or an effective conduit convection mechanism must exist.
DE: 8425 Effusive volcanism
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting