Characteristics of the summit lakes of Ambae volcano and their potential for generating lahars

Abstract

Abstract. Volcanic eruptions through crater lakes often generate lahars, causing loss of life and property. On Ambae volcano, recent eruptive activities have rather tended to reduce the water volume in the crater lake (Lake Voui), in turn, reducing the chances for outburst floods. Lake Voui occupies a central position in the summit caldera and is well enclosed by the caldera relief. Eruptions with significantly higher magnitude than that of 1995 and 2005 are required for an outburst. A more probable scenario for lahar events is the overflow from Lake Manaro Lakua bounded on the eastern side by the caldera wall. Morphology and bathymetry analysis have been used to identify the weakest point of the caldera rim from which water from Lake Manaro Lakua may overflow to initiate lahars. The 1916 disaster described on south-east Ambae was possibly triggered by such an outburst from Lake Manaro Lakua. Taking into account the current level of Lake Manaro Lakua well below a critical overflow point, and the apparently low potential of Lake Voui eruptions to trigger lahars, the Ambae summit lakes may not be directly responsible for numerous lahar deposits identified around the Island.

First estimate of volcanic SO2 budget for Vanuatu island arc

“…8 reveal substantial differences in SO 2 flux from the six studied volcanoes, which primarily reflect their levels of activity. The highest SO 2 emission rate (33 Gg day − 1 ) was recorded at Ambrym during a three-month pulse of strong lava lake degassing in 2005 (Bani et al, 2009a), while the smallest emission rate (9 Mg day − 1 ) is from fumarolic activity on Vanua Lava. Ambrym is a predominantly basaltic volcano, with persistent lava lake activity and a prodigious plume emission that makes it by far the strongest source of SO 2 in Vanuatu ( [Allard et al, 2009] and [Bani et al, 2009a] ).…”

“…A total of 55 days of fieldwork were necessary to assemble this dataset. We integrate here data that have been presented in our previous studies ( [ Bani and Lardy, 2007] , [Bani et al, 2009a] and [Bani et al, 2009b] ) but more than two-thirds of the flux measurements reported here are new (Table 1). Measurement frequency has been strongly determined by access conditions, available funding and serendipity.…”

“…SO 2 flux measurements were made using ultraviolet differential optical absorption spectroscopy (DOAS). At Ambrym, Ambae, Gaua and Lopevi volcanoes, spectroscopic measurements were performed onboard of an aircraft (Brittan-Norman Islander or U206G Cessna), following the traverse method (Bani et al, 2009a), flying just below the volcanic plumes in the cross-wind direction, and with the spectrometer's fiber-coupled telescope pointing to zenith. Flight altitudes ranged from 500 m to 2000 m above sea level.…”

“…Plume speed is a key parameter for flux calculations. During airborne measurements it was obtained using the aircraft navigation system, from the difference in recorded ground speed when flying into and against the wind at the plume altitude (Bani et al, 2009a). For ground-based measurements, wind speed was measured with a hand held anemometer at plume altitude (e.g., the crater rim of Yasur).…”

Lake Pavin Paleolimnology and Event Stratigraphy

“…Maar lakes basin fi lls are frequently considered as key environments for paleoclimate reconstructions (Sifeddine et al 1996 ;Thouveny et al 1994 ;Oldfi eld 1996 ;Ariztegui et al 2001 ;Brauer et al 1999 ;Caballero et al 2006 ;Augustinus et al 2012 ;Zolitschka et al 2013 ) but little is known about the triggering factors of gravity reworking phenomena and related natural hazards (Giresse et al 1991 ;Truze and Kelts 1993 ;Bacon et al 2002 ;Bani et al 2009 ;Zolitschka et al 2013 ). There is particularly a need to improve our understanding of subaquatic slope stabilities, since maar basins are frequently characterized by steep slopes, a conical morphology and no large infl ows (Chap.…”