Abstract:
Eighteen years of heat flux data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to investigate cycles of lava lake activity at Ambrym volcano in Vanuatu. Lava lakes are dynamic manifestations of open-vent volcanic behaviour and time-series analysis of this behaviour reveals the timing and magnitude of magmatic processes. Pulsatory fluctuations in heat flux of > 50 MW over periods of 30 to >100 days during lava lake activity are interpreted to represent episodes of magma replenishment. These are periodically interrupted by rapid falls in heat flux (50–100 MW over <5 days) or variations in the relative heat flux from lava lakes in different vents of the volcano, which are interpreted to represent changes to the shallow plumbing system feeding lava lake activity. Sudden lava lake drainage and flank eruptions can interrupt or terminate lava lake cycles. Heat flux patterns preceding such events do not show an obvious consistent pattern, suggesting that different magmatic processes may initiate these potentially hazardous surges in eruption intensity. Comparison with the dynamics of other lava lakes reveals similarities in long-term behaviour, despite differences in lava lake size, surface motion or degassing. Collectively this suggests fundamental similarities in the processes that sustain open-vent behaviour, including, the stability of magma supply, conduit-plumbing/geometry and local strain-state.
