Gopal K. Mulukutla

The size range of bubbles that produce ash during explosive volcanic eruptions

Volcanic eruptions can produce ash particles with a range of sizes and morphologies. Here we morphologically distinguish two textural types: Simple (generally smaller) ash particles, where the observable surface displays a single measureable bubble because there is at most one vesicle imprint preserved on each facet of the particle; and complex ash particles, which display multiple vesicle imprints on their surfaces for measurement and may contain complete, unfragmented vesicles in their interiors. Digital elevation models from stereo-scanning electron microscopic images of complex ash particles from the 14 October 1974 sub-Plinian eruption of Volcán Fuego, Guatemala and the 18 May 1980 Plinian eruption of Mount St. Helens, Washington, U.S.A. reveal size distributions of bubbles that burst during magma fragmentation. Results were compared between these two well-characterized eruptions of different explosivities and magma compositions and indicate that bubble size distributions (BSDs) are bimodal, suggesting a minimum of two nucleation events during both eruptions. The larger size mode has a much lower bubble number density (BND) than the smaller size mode, yet these few larger bubbles represent the bulk of the total bubble volume. We infer that the larger bubbles reflect an earlier nucleation event (at depth within the conduit) with subsequent diffusive and decompressive bubble growth and possible coalescence during magma ascent, while the smaller bubbles reflect a relatively later nucleation event occurring closer in time to the point of fragmentation. Bubbles in the Mount St. Helens complex ash particles are generally smaller, but have a total number density roughly one order of magnitude higher, compared to the Fuego samples. Results demonstrate that because ash from explosive eruptions preserves the size of bubbles that nucleated in the magma, grew, and then burst during fragmentation, the analysis of the ash-sized component of tephra can provide insights into the spatial distribution of bubbles in the magma prior to fragmentation, enabling better parameterization of numerical eruption models and improved understanding of ash transport phenomena that result in pyroclastic volcanic hazards. Additionally, the fact that the ash-sized component of tephra preserves BSDs and BNDs consistent with those preserved in larger pyroclasts indicates that these values can be obtained in cases where only distal ash samples from particular eruptions are obtainable.

Sizing up the bubbles that produce very fine ash during explosive volcanic eruptions

] Explosive volcanic eruptions emit large proportions ofvery fine ash (<30 mm) into the atmosphere, posing hazardsto aviation, infrastructure, and human health. Here wepresent an analysis of bubble size distributions at the pointof fragmentation during the 18 May 1980 eruption of MSHthrough the examination of simple ash particles in distallydeposited fall samples. The external surfaces of individualfine ash grains preserve the morphology of the bubbles thatburst to form the ash, so bubble sizes can be measuredusing stereo-scanning electron microscopy. Simple ashparticles are those that allow the measurement of a singlevesicle imprint per individual grain. These simple ashparticles are the finest component of the tephra, and canthus travel great distances from the source volcano.Analyses of samples provided bubble volume distributionswith a dominant peak between 560 and 5600 mm

Deployment of a large-scale soil monitoring geosensor network

We provide an overview of our practical experience with developing a distributed sensor network to monitor soil response to climate change and increase our understanding of the complex interactions of the surrounding ecological, biogeochemical and meteorological processes. The network consists of seven sites with unique topographical, and land-use characteristics, spread across a large area in the state of New Hampshire (US). The system was designed to measure soil moisture, soil CO2 efflux and make other ancillary measurements (air temperature, precipitation, wind speed etc.). The system design encompasses sensor and hardware selection, customization and the overcoming design constraints such as the need to operate a power hungry sensing system at remote locations with access only to solar power. The data we collect streams to the web as an outreach and teaching resource, provides input to ecosystem models used to predict how ecosystems in the region will respond to climate and land-use change, and directly monitors soil properties and processes in a changing climate.

Whole object surface area and volume of partial-view 3D models

A technique for estimating a whole object surface area and volume of a micro-scale three-dimensional model with a partially visible surface includes receiving a single-view stereoscopic image of an object of interest and an unconstrained three-dimensional point cloud of the object, generating a constrained three-dimensional point cloud using the image, the unconstrained three-dimensional point cloud, and a digital elevation model (DEM) of the object generated from the image, generating, using the constrained three-dimensional point cloud, a three-dimensional mesh representing an estimate of the surface of the object, calculating a partial surface area and/or partial volume of the object using the three-dimensional mesh, estimating an extent of a visible surface of the object, and calculating a whole surface area and/or a whole volume of the object based on the partial surface area of the object and the estimated extent of the visible surface of the object.