‘Silent’ Dome Emplacement into a Wet Volcano: Observations from an Effusive Eruption at White Island (Whakaari), New Zealand in Late 2012

Abstract

The 2012–2016 White Island (Whakaari) eruption sequence encompassed six small explosive events that included one steam driven and five explosive phreato-magmatic eruptions. More enigmatic, a dome was observed at the back of the vent and crater lake in November 2012. Its emplacement date could not be easily determined due to persistent steam from the evaporating crater lake and because of the very low levels of discrete volcanic earthquakes associated with its growth. During this period, seismicity also included persistent tremor with dominant frequencies in the 2–5 Hz range. Detailed assessment of the tremor reveals a very slow evolution of the spectral peaks from low to higher frequencies. These gliding spectral lines evolved over a three-month time period beginning in late September 2012 and persisting until early January 2013, when the tremor stabilised. As part of the dome emplacement episode, the crater lake progressively dried, leaving isolated pools which then promoted persistent mud/sulphur eruption activity starting in mid-January 2013. We interpret the emplacement of the dome as a non-explosive process where the hot, mostly degassed, magma intruded slowly through the hydrothermal system in late September 2012 and cooled in a relatively quiet state. The tremor evolution might reflect the slow contraction of subsurface resonant cavities, which increased the pitch of the peak resonant frequency through time. Alternatively, spectral evolution might reflect a ‘comb function’ due to clockwork beating of the slowly cooling dome, although direct evidence of clockwork beats is not seen in the waveform data. Finally, it might represent frothing of the hydrothermal system ahead of the slowly propagating magma.

On data reduction methods for volcanic tremor characterization: the 2012 eruption of Copahue volcano, Southern Andes

“…Active volcanic environments are prone to generate long-period sustained seismic signals, known as volcanic tremors. Due to their link with hydrothermal-magmatic systems (e.g., Ripepe and Gordeev 1999;Fujita 2008;Girona et al 2019;Jolly et al 2020), their detection and characterization is a key practice for volcano monitoring (Ogiso et al 2015) and their analysis can, for example, provide insights into the dynamics of phreatic activity (Yukutake et al 2017).…”

Exploring and Modeling the Magma–Hydrothermal Regime

“…White Island Volcano (Whakaari in Te Reo Māori) is a composite, mostly submerged basaltic andesite to dacite volcano characterized by frequent small eruptions and extensive fumarolic activity. Jolly et al [5] describe how magma rose intact through the hydrothermal system and reached the surface in 2012. The ascent is surmised to have begun after ash venting on 2 September and lava was first observed at the surface in late November, all rather quietly.…”

“…The new magma would have also introduced new CO2 into the hydrothermal system, with the result that some geyser activity switched to sub-boiling CO2 bubble-lift (what water well drillers would call airlift) activity, rather than geysering due to boiling White Island Volcano (Whakaari in Te Reo Māori) is a composite, mostly submerged basaltic andesite to dacite volcano characterized by frequent small eruptions and extensive fumarolic activity. Jolly et al [5] describe how magma rose intact through the hydrothermal system and reached the surface in 2012. The ascent is surmised to have begun after ash venting on 2 September and lava was first observed at the surface in late November, all rather quietly.…”

Machine Learning in Volcanology: A Review

“…In many papers also "Tremor episodes" (TRE events) are described and counted, usually associated to magma degassing [20]. However, a volcano with any activity produces a continuous "tremor" which detectability only depends on the seismic instrumentation sensitivity [29,30]. So, the class "TRE" should be better defined as "tremor episode that exceeds the detection limits".…”