the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Oct 2026
First multiparametric observation of a mud volcano eruption
Abstract. Mud volcanoes (MVs) are geological structures emitting a mixture of gas (mostly methane), water, clayey sediments and rock fragments. Their background activity is sometimes interrupted by paroxysmal events, consisting of violent expulsions of huge amounts of these materials, determining geohazard conditions. Although MV eruptions have been reported to have caused damages and casualties worldwide, their surveillance protocols are poorly developed, and multiparametric instrumental recordings of paroxysmal phases have never been documented. Here we show the first-ever multiparametric dataset capturing the pre-, syn-, and post-eruptive evolution of a paroxysmal event at Maccalube di Aragona (Italy) on 29 August 2025. Seismic, geodetic, geomorphological, hydro-meteorological and geochemical data, acquired before, during and after the event allowed to reconstruct the eruption dynamics, identifying indicators for the implementation of monitoring protocols. In particular, variations of physical-chemical parameters of mud pools, soil electric conductivity, seismic tremor and ground deformation shed light on possible precursors, from days to minutes, of the paroxysmal phase.
- Preprint
(1305 KB) - Metadata XML
-
Supplement
(634 KB) - BibTeX
- EndNote
Status: open (until 05 Dec 2026)
-
RC1: 'Comment on egusphere-2026-4985', Anonymous Referee #1, 07 Oct 2026
reply
-
AC1: 'Reply on RC1', Simona Petrosino, 09 Nov 2026
reply
We thank the Reviewer for the positive assessment of work. Please find below our detailed replies (in bold) to his/her comments.
I have some questions about the interpretations. The authors appeal to pressurization as the trigger for the eruption. How is this shown by the data? It seems that only station L, and perhaps O, show a record that could be explained by pressurization (Figure 1 and 2). Why not invert the deformation data for a source model? This is an important issue to explain better as it features prominently in the discussion, and conclusions.
We agree that pressurization is not directly measured in our dataset and cannot be inferred from the GNSS data alone. In the manuscript, pressurization is inferred from the interpretation of the combined multiparametric evidence (Fig. 4), including density drops in the mud-pool water column, soil-EC variance anomalies, changes in seismic tremor, and the post-event fracture/deformation pattern. To make this point clearer and to avoid implying that pressure build-up is uniquely demonstrated by the deformation data we rephrased:
“The concentric fracture pattern, the semi-circular vent alignment, and the long-term deflation inside the caldera-like depression shown by GNSS data, which likely reflects fluid redistribution, all point to pressurization and weakening of the SW sector of the MV field”.
into:“The concentric fracture pattern, the semi-circular vent alignment, and the long-term deflation inside the caldera-like depression shown by GNSS data, which likely reflects fluid redistribution, all point to progressive mechanical weakening and preferential deformation of the SW sector of the MV field.”
About the suggestion of inverting data for extracting a source model, our opinion is that only few measures, irregularly sparse both in space and time are available, making very difficult calculating a deformation source, even roughly determined. Fixing the x,y,z position of the deformation source will need 4-5 sites of measures at least, whose displacements should be driven by the same source. In our specific study case, the deformation vectors are not coherently oriented supposing a punctual deformation source, namely the main mud emission point of the August 2025 paroxysm. In fact, we did not observe a radial deformation pattern centered on the emission point, but very variable moduli and directions, strongly influenced by the local topography and the presence of mechanical discontinuities (the pseudo-caldera rim limiting northward the main vent field), which made very complex the distribution of the deformation field. With so many independent variables controlling the deformation field, the availability of few measures along the observation period, our opinion is that there are not the minimal conditions for executing even a rough data inversion for locating the deformation source, without falling into an overestimation of our data.
More importantly, when referring to pressurization, we do not imply the inflation of a single, centrally located reservoir, as commonly assumed in geodetic models of comparable magmatic volcanic systems. Rather, we refer to pressure variations within the complex feeding system of the Maccalube mud-volcano field, which is likely represented by a distributed network of faults, fractures, and fluid pathways. Such a system cannot readily be represented by a simple central source producing a radial deformation pattern.
In addition, the observed GNSS displacement field does not necessarily reflect deformation associated with fluid-pressure changes alone. Because of the nature of the paroxysmal event, the measured displacements likely result from the superposition of several processes, including mud and debris extrusion, deposition and subsequent compaction of erupted material, changes in surface loading, local collapse and fracturing, redistribution of shallow material, and the mechanical influence of morphological discontinuities such as the scarp delimiting the main emission area.
The expression “overturning” is used to describe the event. What is meant by overturning? And why use this expression?
The term “overturning” is defined in the Introduction, lines 25-30, at its first occurrence in the text. This expression is commonly used in the literature on mud-volcano fields to describe paroxysmal mud eruptions. It derives from the Arabic-derived term maqlūbah, meaning “overturned” or “reversed”, from which the name Maccalube also originates.
Abstract: on the last line, expanding on what is meant by “shed light” would be helpful for readers. What was actually learned?
We clarified this point by rephrasing into: “In particular, variations of physical-chemical parameters of mud pools, soil electric conductivity, seismic tremor and ground deformation identify candidate precursory signals occurring from days to minutes before the paroxysmal phase.”
Line 11, remove “determining geohazard conditions”.
We removed it.
Lines 79-83 can be removed.
Sorry for the typo, we removed it.
Line 167: what is meant by “centrifugal”?
It refers to the spatial distribution of the erupted material. We replaced it with radial.
Citation: https://doi.org/10.5194/egusphere-2026-4985-AC1
-
AC1: 'Reply on RC1', Simona Petrosino, 09 Nov 2026
reply
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 286 | 106 | 49 | 441 | 56 | 42 | 55 |
- HTML: 286
- PDF: 106
- XML: 49
- Total: 441
- Supplement: 56
- BibTeX: 42
- EndNote: 55
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
This manuscript reports geochemical and geophysical data produced by a paroxysmal eruption of a mud volcano. The authors state that this is the first time a mud volcano has before, during, and after eruption data. The descriptions of the monitoring and data are clear.
I have some questions about the interpretations. The authors appeal to pressurization as the trigger for the eruption. How is this shown by the data? It seems that only station L, and perhaps O, show a record that could be explained by pressurization (Figure 1 and 2). Why not invert the deformation data for a source model? This is an important issue to explain better as it features prominently in the discussion, and conclusions.
The expression “overturning” is used to describe the event. What is meant by overturning? And why use this expression?
Abstract: on the last line, expanding on what is meant by “shed light” would be helpful for readers. What was actually learned? Line 11, remove “determining geohazard conditions”.
Lines 79-83 can be removed.
Line 167: what is meant by “centrifugal”?
Overall, a nice study that required forethought and patience. The only recommendation is to take one more step with the data and invert for a source.