Piergiorgio Scarlato - Academia.edu (original) (raw)

Papers by Piergiorgio Scarlato

To illuminate the exsolution of volatiles and the genesis of pyroclasts during Plinian-style volc... more To illuminate the exsolution of volatiles and the genesis of pyroclasts during Plinian-style volcanic eruptions, we performed the first experiments on the flow and fragmentation of a viscoelastic medium under fast, diffusion-driven, bubble expansion. As a magma analogue we use Silly Putty, an American toy made of a viscoelastic silicon polymer. The putty gets saturated by Argon gas under high

The exsolution and expansion of volatiles dissolved in magmas are well acknowledged as the main d... more The exsolution and expansion of volatiles dissolved in magmas are well acknowledged as the main driving force for Plinian-style volcanic eruptions. However, it is still unclear whether magma fragmentation during such activity results from the strain induced by gas expansion within individual bubbles, or from the strain that expansion and acceleration impose to the whole batch of exsolving magma. In

Strombolian explosive activity is generally characterized by a series of short, mild explosions c... more Strombolian explosive activity is generally characterized by a series of short, mild explosions caused by the bursting of large individual gas pockets at the magma free surface; however individual explosions at Stromboli Volcano (Italy) show how these events can be complex and heterogeneous. A new method to study the dynamics of Strombolian eruptions is proposed here, based on the acquisition and elaboration of high-speed videos at Stromboli Volcano. The analysis of high-speed videos of Strombolian explosions reveals previously unreported processes, including pre-and post-explosion crater floor deformation and multiple jet pulses within a single explosion, different explosive styles at individual vents, deformation and fragmentation of in-flight scoria clasts. Video frame elaboration allows us to measure the mass flux, velocity and exit angle of ejecta. In addition, particle velocity trends, in the light of shock tube fragmentation/ejection experiments, may provide information on the source depth of single explosion pulses. These results should be useful for future researches and may help describe quantitatively the dynamics and energetics of Strombolian eruptions, with implications on related hazard assessment.

Strombolian activity is characterized by low-intensity, impulsive explosions, which may occur rep... more Strombolian activity is characterized by low-intensity, impulsive explosions, which may occur repeatedly over long periods of time. Strombolian explosions are thought to result from the bursting of discrete pockets (slugs) of magmatic gas that, deep in the plumbing system, decouple from the surrounding, low-viscosity magma and ascend through it. There are several different physical parameters that control the ascent and explosion of slugs and influence the nature of the resulting geophysical signals, including slug volume, conduit geometry and magma rheology. In this study, we investigate the role of vertical contrasts in magma rheology within the conduit, and the nature of the boundary conditions on magma flow at the top and bottom of the conduit; these parameters have so far received little attention in combination with slug flow. Variations in magma rheology in the conduit are perhaps more a rule than an exception at persistently active volcanoes, where gas-rich, crystal poor magmas share the conduit with their degassed and partially-crystallized counterpart, and where stiffened plugs develop quickly in vents in repose.

Chemical Geology

For a better understanding of the final solidification history of eruptions at Mt. Etna volcano (... more For a better understanding of the final solidification history of eruptions at Mt. Etna volcano (Sicily, Italy), we have investigated cation redistributions at the interface between sub-millimetre-sized clinopyroxene and titanomagnetite crystal rims and coexisting melts. The studied products were scoria clasts from lava fountains and rock samples from pahoehoe and aa lava flows. Our data indicate that scoria clasts from lava fountaining were rapidly quenched at the contact with the atmosphere, preserving the original crystal textures and compositions inherited during magma dynamics within the plumbing system. Kinetics and energetics of crystallization were instantaneously frozen-in and post-eruptive effects on mineral chemistry were negligible. The near-equilibrium compositions of clinopyroxene and titanomagnetite indicate that lava fountain episodes were supplied by high-temperature, H2O-rich magmas ascending with velocities of 0.01-0.31 m/s. In contrast, magmas feeding lava flow e...

Such explosions are characterised by a first bomb-rich ash-poor pulse, followed by the the emissi... more Such explosions are characterised by a first bomb-rich ash-poor pulse, followed by the the emission of concentrated ash and pyroclasts. These eruptions can last up to 40 seconds, much longer then the previous (usually lasting than 10 seconds).

content: Dynamics of strombolian eruptions at Batu Tara volcano (Indonesia). In September 2014, h... more content: Dynamics of strombolian eruptions at Batu Tara volcano (Indonesia). In September 2014, high­speed imaging and acoustic data were acquired at Batu Tara volcano (Indonesia) during a field experiment aimed at investigating its degassing and explosive dynamics. The small isolated island of Batu Tara in the Flores Sea (about 50 km N of Lembata) is very similar to the Italian Stromboli Volcano in both eruptive style and edifice morphology. It is characterized by several strong episodic strombolian and vulcanian eruptions with recurrence time of minutes to hours. We temporarily deployed in direct view of the active vent one high­speed visible camera acquiring images at 500 frames per second (fps), one thermal infrared (FLIR) camera acquiring at 50­200 fps, two broadband microphones (range of tens of kHz to 0.1 Hz), synchronized with the cameras, one visible time­lapse camera. The main information retrieved from the observations are: i) gas and pyroclast ejection processes, their a...

Seismic and acoustic surveillance is routinely performed at several persistent activity volcanoes... more Seismic and acoustic surveillance is routinely performed at several persistent activity volcanoes worldwide. However, interpretation of the signals associated with explosive activity is still equivocal, due to both source variability and the intrinsically limited information carried by the waves. Comparison and cross­correlation of the geophysical quantities with other information in general and visual recording in particular is therefore actively sought. In July 2014 Strombolian­style explosive activity occurred at two adjoined vents formed along a new eruptive fissure. Visually, the activity appeared as short­lived explosions ejecting bomb­ to lapilli­sized, molten pyroclasts at a remarkably repeatable time interval. The frequent occurrence and the highly repeatable nature of the explosions provided us with a rare occasion to systematically investigate the seismic and acoustic fields radiated by this common volcanic source. During July 15 and 16, 2014 we deployed FAMoUS (FAst, MUl...

The electrical conductivity of geomaterials can vary by several orders of magnitude over small ch... more The electrical conductivity of geomaterials can vary by several orders of magnitude over small changes in temperature and/or chemical composition. The variation in electrical conductivity of Earth's mantle is largely dependent on temperature as it increases from approximately 0.01 S/m in the upper mantle to 1 S/m in the shallow depths of the warmer lower mantle. Activation energies for electrical conduction of iron-bearing silicate minerals are on the order of 1 eV and depend mostly on Fe and H2O contents. Over a more restricted temperature range, the importance of chemical composition on the conductivity of natural silicate melts is much more evident. From a database of several experimental data we have generated an empirical model for the electrical conductivity of natural silicate melts as a function of chemical composition and temperature. The data include those obtained in our laboratory and others taken from the literature. All melts are anhydrous and we take into account ...

Volcanic jets of pyroclasts and hot gases are injected in the atmosphere during explosive eruptio... more Volcanic jets of pyroclasts and hot gases are injected in the atmosphere during explosive eruptions. Despite aerodynamic gas-pyroclast interactions exert a prime control on eruption dynamics and pyroclast emplacement, field-based parameterization from direct measurements are still challenging. Here, we report detailed measurements of pyroclast and gas motion in volcanic jets from persistent activity at Stromboli volcano. High-speed videos were collected at 500 frames per second with a resolution of 1.7 cm/pixel in an area of 9x9 m right above the active vents in June 2009. Images of ash-free jets allowed the tracking of individual pyroclasts and to outline the velocity field from the core to the margins of the jet, while specific video-processing evidenced the motion of the ambient air upon entrainment at the jet boundaries. Overall, fluctuating gas-pyroclast velocity trends reveal the pulsating nature of Strombolian jets. The front of the jet shows initial velocities in the order o...

Istituto nazionale di geofisica e vulcanologia (pierreyves.tournigand@ingv.it) Subaerial explosiv... more Istituto nazionale di geofisica e vulcanologia (pierreyves.tournigand@ingv.it) Subaerial explosive volcanic activity ejects a mixture of gas-ash-pyroclasts in the atmosphere. Parameterizing the physical processes responsible for ash injection and plume dynamics is crucial to constrain numerical models and forecasts of potentially hazardous ash dispersal events. In this study we present preliminary results from a new method based on visible and thermal high-speed video processing from Strombolian and Vulcanian explosions. High-speed videos were recorded by a Optronis CR600x2 camera (1280x1024 pixels definition, 500 Hz frame rate) for the visible and by a FLIR SC655 (640x480 pixels definition, 50 Hz frame rate) for the thermal. Qualitatively, different dynamics of ash injection and dispersal can be identified. High speed cameras allow us to observe all the different phases during volcanic plume dispersion with a very good time resolution. Multiple features were already observed about ...

Recent advancements in the use of high speed thermal and visible cameras allowed a precise quanti... more Recent advancements in the use of high speed thermal and visible cameras allowed a precise quantification of key parameters of explosive eruptions. However, the large volume of video data poses several processing issues and hinders parameter extraction. In this methodological investigation we show how computing techniques based on Particle Image Velocimetry (PIV, measuring the displacement of sub-areas of an image between successive frames by correlating features identified in any sub-area) and Particle Tracking Velocimetry (PTV, detecting and tracking single particles along a series of images) allows for the automatic processing of high-speed videos and explosion parameterization. We developed a 3-steps automatized routine for volcanic high-speed video processing. Step 1 pre-processes the images, removing image background with different techniques to improve image contrast and possibly accounting for camera shaking. Step 2 involves running the custom-made PTV and PIV softwares. Ste...

Strombolian activity style is characterised by discrete explosions at variable frequency, lasting... more Strombolian activity style is characterised by discrete explosions at variable frequency, lasting a few to tens of seconds, and ejecting pyroclasts at heights of tens to hundreds of meters. New imaging techniques, including high speed camera observations, have already shown that these explosions are complex phenomena that include pyroclast ejection pulses, typically lasting tenths of seconds, characterized by a non-linear decay on the ejection velocity over time and related to individual pressure release events. Here, we show the results of a new computing techniques (described in a companion abstract, Eruptions on Fast Track, part a), based on joint application of Particle Image Velocimetry (PIV, providing information on the ash and gas clouds) and Particle Tracking Velocimetry (PTV, providing information on the cm-to m-sized pyroclasts) to high-speed visible and thermal videos of Strombolian explosions at Stromboli (Italy) and Yasur (Vanuatu) volcanoes. In comparison to previous s...

The mechanics of earthquakes and faulting is a multidisciplinary topic involving seismologists, g... more The mechanics of earthquakes and faulting is a multidisciplinary topic involving seismologists, geologists and rock deformation experimentalists. The main difficulty in reconciling multidisciplinary observations is the scale dependence that characterizes the underlying physical processes. To tackle this challenge the first prerequisite is the availability of high resolution data collected near the causative sources: this implies the access to state-of-the-art research infrastructures (e.g. rock deformation laboratories) and observation systems (e.g. dense seismic networks). The GLASS project, funded by the European Research Council Starting Independent Research Grant, is centered on two innovative aspects. First, we have been developing a state-of-the-art biaxial deformation apparatus within a pressure vessel. The machine will be able to work on large blocks of rocks (up to 20 x 20 cm) and to characterize fluid flow and frictional properties of faults over a wide spectrum of realist...

Lava lakes offer unique opportunities for understanding how magmatic volatiles physically escape ... more Lava lakes offer unique opportunities for understanding how magmatic volatiles physically escape from lowviscosity, vesicular magma in openvent conditions, a process often referred to as magma outgassing. Largescale lava convection movements and meter scale bubble explosions, sometimes triggered by rock falls, are acknowledged outgassing processes but may not be the only ones. In 2013 we used highfrequency (50500 Hz) thermal and visible imaging to investigate the shorttimescale dynamics of the currently active Halema`uma`u lava lake. At that time, besides the dominant release of large bubbles, three types of peculiar outgassing features were observed on the lava lake surface. The first, diffusely observed throughout the observation experiment, consisted of prolonged (up to seconds) gas venting from 'spot vents'. These vents appeared to open and close without the ejection of material or bubble bursting, and were the site of hot gas emission. Spot vents were located both between and inside cooling plates, and followed the general circulation pattern together with the rest of the lava lake surface. The second feature, observed only once, consisted of the transient wobbling of the whole lava lake surface. This wobbling, with a wavelength of meters to tens of meters, was not related to any external trigger, and dampened soon without apparent consequences on the other lake dynamics. Finally, we observed large (meters) doming areas of the lake surface randomly fluctuating over seconds to minutes. These areas were either stationary or moved independently of the general lake surface circulation, and usually were not affected by other lake surface features (e.g., cooling plate boundaries). These three features, though trivial for the overall lake outgassing, testify that the lava lake has a complex shallow subsurface architecture, in which permeable channels and gas pockets act independently of the more common bubble bursts.

To illuminate the exsolution of volatiles and the genesis of pyroclasts during Plinian-style volc... more To illuminate the exsolution of volatiles and the genesis of pyroclasts during Plinian-style volcanic eruptions, we performed the first experiments on the flow and fragmentation of a viscoelastic medium under fast, diffusion-driven, bubble expansion. As a magma analogue we use Silly Putty, an American toy made of a viscoelastic silicon polymer. The putty gets saturated by Argon gas under high

The exsolution and expansion of volatiles dissolved in magmas are well acknowledged as the main d... more The exsolution and expansion of volatiles dissolved in magmas are well acknowledged as the main driving force for Plinian-style volcanic eruptions. However, it is still unclear whether magma fragmentation during such activity results from the strain induced by gas expansion within individual bubbles, or from the strain that expansion and acceleration impose to the whole batch of exsolving magma. In

Strombolian explosive activity is generally characterized by a series of short, mild explosions c... more Strombolian explosive activity is generally characterized by a series of short, mild explosions caused by the bursting of large individual gas pockets at the magma free surface; however individual explosions at Stromboli Volcano (Italy) show how these events can be complex and heterogeneous. A new method to study the dynamics of Strombolian eruptions is proposed here, based on the acquisition and elaboration of high-speed videos at Stromboli Volcano. The analysis of high-speed videos of Strombolian explosions reveals previously unreported processes, including pre-and post-explosion crater floor deformation and multiple jet pulses within a single explosion, different explosive styles at individual vents, deformation and fragmentation of in-flight scoria clasts. Video frame elaboration allows us to measure the mass flux, velocity and exit angle of ejecta. In addition, particle velocity trends, in the light of shock tube fragmentation/ejection experiments, may provide information on the source depth of single explosion pulses. These results should be useful for future researches and may help describe quantitatively the dynamics and energetics of Strombolian eruptions, with implications on related hazard assessment.

Strombolian activity is characterized by low-intensity, impulsive explosions, which may occur rep... more Strombolian activity is characterized by low-intensity, impulsive explosions, which may occur repeatedly over long periods of time. Strombolian explosions are thought to result from the bursting of discrete pockets (slugs) of magmatic gas that, deep in the plumbing system, decouple from the surrounding, low-viscosity magma and ascend through it. There are several different physical parameters that control the ascent and explosion of slugs and influence the nature of the resulting geophysical signals, including slug volume, conduit geometry and magma rheology. In this study, we investigate the role of vertical contrasts in magma rheology within the conduit, and the nature of the boundary conditions on magma flow at the top and bottom of the conduit; these parameters have so far received little attention in combination with slug flow. Variations in magma rheology in the conduit are perhaps more a rule than an exception at persistently active volcanoes, where gas-rich, crystal poor magmas share the conduit with their degassed and partially-crystallized counterpart, and where stiffened plugs develop quickly in vents in repose.

Chemical Geology

For a better understanding of the final solidification history of eruptions at Mt. Etna volcano (... more For a better understanding of the final solidification history of eruptions at Mt. Etna volcano (Sicily, Italy), we have investigated cation redistributions at the interface between sub-millimetre-sized clinopyroxene and titanomagnetite crystal rims and coexisting melts. The studied products were scoria clasts from lava fountains and rock samples from pahoehoe and aa lava flows. Our data indicate that scoria clasts from lava fountaining were rapidly quenched at the contact with the atmosphere, preserving the original crystal textures and compositions inherited during magma dynamics within the plumbing system. Kinetics and energetics of crystallization were instantaneously frozen-in and post-eruptive effects on mineral chemistry were negligible. The near-equilibrium compositions of clinopyroxene and titanomagnetite indicate that lava fountain episodes were supplied by high-temperature, H2O-rich magmas ascending with velocities of 0.01-0.31 m/s. In contrast, magmas feeding lava flow e...

Such explosions are characterised by a first bomb-rich ash-poor pulse, followed by the the emissi... more Such explosions are characterised by a first bomb-rich ash-poor pulse, followed by the the emission of concentrated ash and pyroclasts. These eruptions can last up to 40 seconds, much longer then the previous (usually lasting than 10 seconds).

content: Dynamics of strombolian eruptions at Batu Tara volcano (Indonesia). In September 2014, h... more content: Dynamics of strombolian eruptions at Batu Tara volcano (Indonesia). In September 2014, high­speed imaging and acoustic data were acquired at Batu Tara volcano (Indonesia) during a field experiment aimed at investigating its degassing and explosive dynamics. The small isolated island of Batu Tara in the Flores Sea (about 50 km N of Lembata) is very similar to the Italian Stromboli Volcano in both eruptive style and edifice morphology. It is characterized by several strong episodic strombolian and vulcanian eruptions with recurrence time of minutes to hours. We temporarily deployed in direct view of the active vent one high­speed visible camera acquiring images at 500 frames per second (fps), one thermal infrared (FLIR) camera acquiring at 50­200 fps, two broadband microphones (range of tens of kHz to 0.1 Hz), synchronized with the cameras, one visible time­lapse camera. The main information retrieved from the observations are: i) gas and pyroclast ejection processes, their a...

Seismic and acoustic surveillance is routinely performed at several persistent activity volcanoes... more Seismic and acoustic surveillance is routinely performed at several persistent activity volcanoes worldwide. However, interpretation of the signals associated with explosive activity is still equivocal, due to both source variability and the intrinsically limited information carried by the waves. Comparison and cross­correlation of the geophysical quantities with other information in general and visual recording in particular is therefore actively sought. In July 2014 Strombolian­style explosive activity occurred at two adjoined vents formed along a new eruptive fissure. Visually, the activity appeared as short­lived explosions ejecting bomb­ to lapilli­sized, molten pyroclasts at a remarkably repeatable time interval. The frequent occurrence and the highly repeatable nature of the explosions provided us with a rare occasion to systematically investigate the seismic and acoustic fields radiated by this common volcanic source. During July 15 and 16, 2014 we deployed FAMoUS (FAst, MUl...

The electrical conductivity of geomaterials can vary by several orders of magnitude over small ch... more The electrical conductivity of geomaterials can vary by several orders of magnitude over small changes in temperature and/or chemical composition. The variation in electrical conductivity of Earth's mantle is largely dependent on temperature as it increases from approximately 0.01 S/m in the upper mantle to 1 S/m in the shallow depths of the warmer lower mantle. Activation energies for electrical conduction of iron-bearing silicate minerals are on the order of 1 eV and depend mostly on Fe and H2O contents. Over a more restricted temperature range, the importance of chemical composition on the conductivity of natural silicate melts is much more evident. From a database of several experimental data we have generated an empirical model for the electrical conductivity of natural silicate melts as a function of chemical composition and temperature. The data include those obtained in our laboratory and others taken from the literature. All melts are anhydrous and we take into account ...

Volcanic jets of pyroclasts and hot gases are injected in the atmosphere during explosive eruptio... more Volcanic jets of pyroclasts and hot gases are injected in the atmosphere during explosive eruptions. Despite aerodynamic gas-pyroclast interactions exert a prime control on eruption dynamics and pyroclast emplacement, field-based parameterization from direct measurements are still challenging. Here, we report detailed measurements of pyroclast and gas motion in volcanic jets from persistent activity at Stromboli volcano. High-speed videos were collected at 500 frames per second with a resolution of 1.7 cm/pixel in an area of 9x9 m right above the active vents in June 2009. Images of ash-free jets allowed the tracking of individual pyroclasts and to outline the velocity field from the core to the margins of the jet, while specific video-processing evidenced the motion of the ambient air upon entrainment at the jet boundaries. Overall, fluctuating gas-pyroclast velocity trends reveal the pulsating nature of Strombolian jets. The front of the jet shows initial velocities in the order o...

Istituto nazionale di geofisica e vulcanologia (pierreyves.tournigand@ingv.it) Subaerial explosiv... more Istituto nazionale di geofisica e vulcanologia (pierreyves.tournigand@ingv.it) Subaerial explosive volcanic activity ejects a mixture of gas-ash-pyroclasts in the atmosphere. Parameterizing the physical processes responsible for ash injection and plume dynamics is crucial to constrain numerical models and forecasts of potentially hazardous ash dispersal events. In this study we present preliminary results from a new method based on visible and thermal high-speed video processing from Strombolian and Vulcanian explosions. High-speed videos were recorded by a Optronis CR600x2 camera (1280x1024 pixels definition, 500 Hz frame rate) for the visible and by a FLIR SC655 (640x480 pixels definition, 50 Hz frame rate) for the thermal. Qualitatively, different dynamics of ash injection and dispersal can be identified. High speed cameras allow us to observe all the different phases during volcanic plume dispersion with a very good time resolution. Multiple features were already observed about ...

Recent advancements in the use of high speed thermal and visible cameras allowed a precise quanti... more Recent advancements in the use of high speed thermal and visible cameras allowed a precise quantification of key parameters of explosive eruptions. However, the large volume of video data poses several processing issues and hinders parameter extraction. In this methodological investigation we show how computing techniques based on Particle Image Velocimetry (PIV, measuring the displacement of sub-areas of an image between successive frames by correlating features identified in any sub-area) and Particle Tracking Velocimetry (PTV, detecting and tracking single particles along a series of images) allows for the automatic processing of high-speed videos and explosion parameterization. We developed a 3-steps automatized routine for volcanic high-speed video processing. Step 1 pre-processes the images, removing image background with different techniques to improve image contrast and possibly accounting for camera shaking. Step 2 involves running the custom-made PTV and PIV softwares. Ste...

Strombolian activity style is characterised by discrete explosions at variable frequency, lasting... more Strombolian activity style is characterised by discrete explosions at variable frequency, lasting a few to tens of seconds, and ejecting pyroclasts at heights of tens to hundreds of meters. New imaging techniques, including high speed camera observations, have already shown that these explosions are complex phenomena that include pyroclast ejection pulses, typically lasting tenths of seconds, characterized by a non-linear decay on the ejection velocity over time and related to individual pressure release events. Here, we show the results of a new computing techniques (described in a companion abstract, Eruptions on Fast Track, part a), based on joint application of Particle Image Velocimetry (PIV, providing information on the ash and gas clouds) and Particle Tracking Velocimetry (PTV, providing information on the cm-to m-sized pyroclasts) to high-speed visible and thermal videos of Strombolian explosions at Stromboli (Italy) and Yasur (Vanuatu) volcanoes. In comparison to previous s...

The mechanics of earthquakes and faulting is a multidisciplinary topic involving seismologists, g... more The mechanics of earthquakes and faulting is a multidisciplinary topic involving seismologists, geologists and rock deformation experimentalists. The main difficulty in reconciling multidisciplinary observations is the scale dependence that characterizes the underlying physical processes. To tackle this challenge the first prerequisite is the availability of high resolution data collected near the causative sources: this implies the access to state-of-the-art research infrastructures (e.g. rock deformation laboratories) and observation systems (e.g. dense seismic networks). The GLASS project, funded by the European Research Council Starting Independent Research Grant, is centered on two innovative aspects. First, we have been developing a state-of-the-art biaxial deformation apparatus within a pressure vessel. The machine will be able to work on large blocks of rocks (up to 20 x 20 cm) and to characterize fluid flow and frictional properties of faults over a wide spectrum of realist...

Lava lakes offer unique opportunities for understanding how magmatic volatiles physically escape ... more Lava lakes offer unique opportunities for understanding how magmatic volatiles physically escape from lowviscosity, vesicular magma in openvent conditions, a process often referred to as magma outgassing. Largescale lava convection movements and meter scale bubble explosions, sometimes triggered by rock falls, are acknowledged outgassing processes but may not be the only ones. In 2013 we used highfrequency (50500 Hz) thermal and visible imaging to investigate the shorttimescale dynamics of the currently active Halema`uma`u lava lake. At that time, besides the dominant release of large bubbles, three types of peculiar outgassing features were observed on the lava lake surface. The first, diffusely observed throughout the observation experiment, consisted of prolonged (up to seconds) gas venting from 'spot vents'. These vents appeared to open and close without the ejection of material or bubble bursting, and were the site of hot gas emission. Spot vents were located both between and inside cooling plates, and followed the general circulation pattern together with the rest of the lava lake surface. The second feature, observed only once, consisted of the transient wobbling of the whole lava lake surface. This wobbling, with a wavelength of meters to tens of meters, was not related to any external trigger, and dampened soon without apparent consequences on the other lake dynamics. Finally, we observed large (meters) doming areas of the lake surface randomly fluctuating over seconds to minutes. These areas were either stationary or moved independently of the general lake surface circulation, and usually were not affected by other lake surface features (e.g., cooling plate boundaries). These three features, though trivial for the overall lake outgassing, testify that the lava lake has a complex shallow subsurface architecture, in which permeable channels and gas pockets act independently of the more common bubble bursts.