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Time scales of volcanic unrest and dynamics of magma ascent

Petrological studies can inform of the processes and time scales of magma movement and ascent, and thus allow associating them with monitoring unrest signals, and thus better mitigate volcano hazards. This year we made significant progress in linking time scales and monitoring data for Kelut 1990 eruption, and found that crystals mainly record magma ascent rather than intrusion.

This is a grayscale image of spinel crystals collected from lavas emitted during an eruption of Mayon volcano in the Philippines. The brightness of the image reflects the relative abundance of iron. The darker grey lines we see within the spinel tell us that these crystals have resided in a magma for long periods of time. This information combined with the chemistry of other minerals like orthopyroxene and plagioclase helps us build a picture of what the magma chamber looked like before eruptions (Source: Dawn C. S. Ruth)

False colour image of a zoned orthopyroxene crystal (orange mineral) and magnetite (white mineral) surrounded by melt (blue) from a pumice erupted in 1990 from Kelud volcano, Indonesia. Measuring compositional changes across mineral zones allow scientists to model timescales of pre-eruptive processes for volcanoes like Kelud.

F-Cl-OH compositions of apatite occurring in different textural positions from the 2006 and 2010 Merapi samples. Scale bar is 100 m for the three BSE images on the left, and 10 m for the image on the right. Abbreviations accompanied by symbols on the right are: hbl, hornblende; cpx, clinopyroxene; plag, plagioclase; GM, groundmass. Apatite included in hornblende from both deposits (2006-hbl, 2010-hbl, in red solid-line ellipse) show distinctly higher OH contents than crystals hosted by other minerals or in the groundmass (in black dashed-line box). Apatite data from literature 1Peng et al. (1007); 2Scott et al. (2015); 3Stock et al. (2016); 4Boyce and Hervig (2008); 5Piccoli and Candela (2002); 6Boudreau (1995); 7Kusebauch et al. (2015) (Source: Weiran Li)

CO2, H2O and S concentrations in apatite from the 2006 and 2010 deposits of Merapi, measured using secondary ion microprobe (SIMS). Apatite standards and compositions, including CO2, were measured by Clark et al. (2016). Analyses background is <10ppm H2O, and ~20-30ppm CO2. Errors are marked with black solid line or are smaller than the symbols. All apatite included in amphibole (2010-hbl, 2006-hbl) show higher S contents (in red solid-line ellipse), among which the 2010 apatite in hbl (indicated by yellow diamonds) show the highest S and CO2 concentrations, indicating volatile-rich magma in the deeper reservoir. Abbreviations accompanied by symbols are: hbl, hornblende; cpx, clinopyroxene; plag, plagioclase; GM, groundmass (Source: Weiran Li)

Funding Sources:

Earth Observatory of Singapore
Stephen Riady Geoscience Fund

Project Years:

2016

2017

2018

Causes, Processes, and Forecasts of Eruptions of Open Vent Volcanoes in Southeast Asia

Using an approach that integrates geochemistry, mineralogy, numerical modelling, and physical models, this project aims to improve open-vent volcano forecasts in Southeast Asia.