Abstract
Persistent non-explosive passive degassing is a common characteristic of active volcanoes. Distinct periodic components in measurable parameters of gas release have been widely identified over timescales ranging from seconds to months. The development and implementation of high temporal resolution gas measurement techniques now enables the robust quantification of high frequency processes operating on timescales comparable to those detectable in geophysical datasets. This review presents an overview of the current state of understanding regarding periodic volcanic degassing, and evaluates the methods available for detecting periodicity, e.g., autocorrelation, variations of the Fast Fourier Transform (FFT), and the continuous wavelet transform (CWT). Periodicities in volcanic degassing from published studies were summarised and statistically analysed together with analyses of literature-derived datasets where periodicity had not previously been investigated. Finally, an overview of current knowledge on drivers of periodicity was presented and discussed in the framework of four main generating categories, including: (1) non-volcanic (e.g., atmospheric or tidally generated); (2) gas-driven, shallow conduit processes; (3) magma movement, intermediate to shallow storage zone; and (4) deep magmatic processes.
Highlights
IntroductionActive volcanoes commonly exhibit persistent (i.e., continuous or quasi-continuous) emission of gases from summit vents or fumaroles (Figure 1)
Active volcanoes commonly exhibit persistent emission of gases from summit vents or fumaroles (Figure 1)
Stationarity required within an individual analysis window; but, can visualise non-stationary periodicity when employed in the form of the short-term Fourier transform (STFT) moving window method
Summary
Active volcanoes commonly exhibit persistent (i.e., continuous or quasi-continuous) emission of gases from summit vents or fumaroles (Figure 1). Could at with best achieve resolutions of minutes because of the need at to frequencies traverse or scan gas plumes [12,13,14]. Whilst low frequency periodic components are widely to originate from deep processes[21]. Related to large-scale magma movement [22,23], are widely thought to originate from deep processes large-scale magma movement [22,23], high frequency signals can be derived from a wide related range oftopotential drivers [16]. Transform Infrared Spectroscopy (OP-FTIR) can capture high temporal resolution datasets ofa molar range of gases, including trace speciesincluding such as chlorine [28,29,30,31,32].
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