More Like this

1. Avalanche dynamics in sheared athermal particle packings occurs via localized bursts predicted by unstable linear response

   https://doi.org/10.1039/D1SM01451J  

   Stanifer, Ethan; Manning, M. Lisa (March 2022, Soft Matter)

   Under applied shear strain, granular and amorphous materials deform via particle rearrangements, which can be small and localized or organized into system-spanning avalanches. While the statistical properties of avalanches under quasi-static shear are well-studied, the dynamics during avalanches is not. In numerical simulations of sheared soft spheres, we find that avalanches can be decomposed into bursts of localized deformations, which we identify using an extension of persistent homology methods. We also study the linear response of unstable systems during an avalanche, demonstrating that eigenvalue dynamics are highly complex during such events, and that the most unstable eigenvector is a poor predictor of avalanche dynamics. Instead, we modify existing tools that identify localized excitations in stable systems, and apply them to these unstable systems with non-positive definite Hessians, quantifying the evolution of such excitations during avalanches. We find that bursts of localized deformations in the avalanche almost always occur at localized excitations identified using the linear spectrum. These new tools will provide an improved framework for validating and extending mesoscale elastoplastic models that are commonly used to explain avalanche statistics in glasses and granular matter. 

   more » « less
2. Many-Body Resonances in the Avalanche Instability of Many-Body Localization

   https://doi.org/10.1103/PhysRevLett.130.250405  

   Ha, Hyunsoo; Morningstar, Alan; Huse, David A. (June 2023, Physical Review Letters)

   Many-body localized (MBL) systems fail to reach thermal equilibrium under their own dynamics, even though they are interacting, nonintegrable, and in an extensively excited state. One instability toward thermalization of MBL systems is the so-called “avalanche,” where a locally thermalizing rare region is able to spread thermalization through the full system. The spreading of the avalanche may be modeled and numerically studied in finite one-dimensional MBL systems by weakly coupling an infinite-temperature bath to one end of the system. We find that the avalanche spreads primarily via strong many-body resonances between rare near-resonant eigenstates of the closed system. Thus we find and explore a detailed connection between many-body resonances and avalanches in MBL systems. 

   more » « less
3. Avalanche scaling in large neural populations with distributed coupling to multiple dynamical latent variables

   Morrell, Mia C.; Nemenman, Ilya; Sederberg, Audrey J. (January 2023, arXiv)

   Observations of power laws in neural activity data have raised the intriguing notion that brains may operate in a critical state. One example of this critical state is "avalanche criticality," which has been observed in a range of systems, including cultured neurons, zebrafish, and human EEG. More recently, power laws have also been observed in neural populations in the mouse under a coarse-graining procedure, and they were explained as a consequence of the neural activity being coupled to multiple latent dynamical variables. An intriguing possibility is that avalanche criticality emerges due to a similar mechanism. Here, we determine the conditions under which dynamical latent variables give rise to avalanche criticality. We find that a single, quasi-static latent variable can generate critical avalanches, but that multiple latent variables lead to critical behavior in a broader parameter range. We identify two regimes of avalanches, both of which are critical, but differ in the amount of information carried about the latent variable. Our results suggest that avalanche criticality arises in neural systems in which there is an emergent dynamical variable or shared inputs creating an effective latent dynamical variable, and when this variable can be inferred from the population activity. 

   more » « less
4. Reconstructing the dynamics of the highly similar May 2016 and June 2019 Iliamna Volcano (Alaska) ice–rock avalanches from seismoacoustic data

   https://doi.org/10.5194/esurf-9-271-2021  

   Toney, Liam; Fee, David; Allstadt, Kate E.; Haney, Matthew M.; Matoza, Robin S. (January 2021, Earth Surface Dynamics)

   null (Ed.)

   Abstract. Surficial mass wasting events are a hazard worldwide. Seismic and acoustic signals from these often remote processes, combined with other geophysical observations, can provide key information for monitoring and rapid response efforts and enhance our understanding of event dynamics. Here, we present seismoacoustic data and analyses for two very large ice–rock avalanches occurring on Iliamna Volcano, Alaska (USA), on 22 May 2016 and 21 June 2019. Iliamna is a glacier-mantled stratovolcano located in the Cook Inlet, ∼200 km from Anchorage, Alaska. The volcano experiences massive, quasi-annual slope failures due to glacial instabilities and hydrothermal alteration of volcanic rocks near its summit. The May 2016 and June 2019 avalanches were particularly large and generated energetic seismic and infrasound signals which were recorded at numerous stations at ranges from ∼9 to over 600 km. Both avalanches initiated in the same location near the head of Iliamna's east-facing Red Glacier, and their ∼8 km long runout shapes are nearly identical. This repeatability – which is rare for large and rapid mass movements – provides an excellent opportunity for comparison and validation of seismoacoustic source characteristics. For both events, we invert long-period (15–80 s) seismic signals to obtain a force-time representation of the source. We model the avalanche as a sliding block which exerts a spatially static point force on the Earth. We use this force-time function to derive constraints on avalanche acceleration, velocity, and directionality, which are compatible with satellite imagery and observed terrain features. Our inversion results suggest that the avalanches reached speeds exceeding 70 m s−1, consistent with numerical modeling from previous Iliamna studies. We lack sufficient local infrasound data to test an acoustic source model for these processes. However, the acoustic data suggest that infrasound from these avalanches is produced after the mass movement regime transitions from cohesive block-type failure to granular and turbulent flow – little to no infrasound is generated by the initial failure. At Iliamna, synthesis of advanced numerical flow models and more detailed ground observations combined with increased geophysical station coverage could yield significant gains in our understanding of these events. 

   more » « less
5. Plant Community Assembly on Volcanic Debris Avalanche Deposits around the World

   https://doi.org/10.1139/er-2025-0079  

   Denton, Elsie Mariah; Dale, Virginia H (September 2025, Environmental Reviews)

   Volcanic debris avalanches are among the largest and most severe disturbances known. Therefore, studying processes of ecosystem formation on the deposits emplaced by these landslides provides insights into the patterns of community assembly after the most severe disruptions. In this review we synthesize findings of 60 vegetation studies from 15 volcanic debris avalanche deposits. One of the most impactful drivers of the speed with which communities reestablish is the climatic region in which the debris avalanche occurs. The fastest recovery occurs in the tropics and slowest in the boreal latitudes. The existence of biotic legacies, or remnant soils or biota from the previous communities accelerates community establishment, and these legacies are found more frequently on smaller debris avalanche deposits. Where these legacies exist, recovery proceeds many times more rapidly than in primary successional areas of the deposits. Similar patterns across mountains are observed in the species guilds that arrive and become established on the deposits with nitrogen fixers and early seral species doing particularly well. Complete recovery, meaning that communities match those of surrounding undisturbed areas, from this extreme class of disturbance takes a very long time, decades in the tropics and centuries to millennia at higher latitudes. Secondary disturbances are frequent and often reshape the direction of community development. Understanding of community development on debris avalanches would be greatly expanded if continuous time series over decadal to millennial scales were available on more disturbances. This could be achieved through repeat monitoring of permanent plots, remote sensing, or use of pollen core analysis. Such studies may enable inference about whether long-lasting community differences from surrounding areas are due to alternative stable states or simply the slow turnover of long-lived species on volcanic debris avalanches. Further study of these topics will foster better management of human disturbed landscapes, such as those from large-scale mining. 

   more » « less