Fig. 6: Relationship between SO₂ mass and magma volume across different magma types, emphasizing basaltic gas-rich events.

A Relationship between SO₂ mass and the corresponding magma volume sustaining past eruptive events. It distinguishes the magnitude of gas output during eruptive events as a function of magma type. The blue, black and red lines are regression lines between SO₂ releases during eruptions and corresponding magma source volumes for basalt, andesite and dacite respectively. The dashed lines are included to clearly distinguish the individual eruptions for better visualization. Bezymianny (1956) and Nevado del Ruiz (1985) eruptions were gas-rich events, whilst Soufrière Hills eruption (1995–1998) was a gas-poor event for andesitic magma. Agung (1963) and Arenal (1985–1996) eruptions are gas-rich events contrasting with Galunggung (1982-1983) for basaltic-andesite magma. Similarly, in the case of basaltic magma, Ambae 2017–2018 eruption stands out as a gas-rich event. The relatively calm phases contributed significantly to the overall release of SO₂. Ambrym’s situation in 2005–2015 shares this same analysis with its annual 2.5 Tg of SO₂⁶² while the 2018 eruption was gas-poor event suggesting a degassed source. Dacite magmas are poor-gas source. Data are recalculated from ref. ³⁶.