Volcanoes release plumes of gas and ash to the atmosphere during episodes of passive and explosive behavior. These ejecta have important implications for the chemistry and composition of the troposphere and stratosphere, with the capacity to alter Earth's radiation budget and climate system over a range of temporal and spatial scales. Volcanogenic sulphur dioxide reacts to form sulphate aerosols, which increase global albedo, e.g., by reducing surface temperatures, in addition to perturbing the formation processes and optical properties of clouds. Released halogen species can also deplete stratospheric and tropospheric ozone. Volcanic degassing, furthermore, played a key role in the formation of Earth’s atmosphere, and volcanic plumes can affect air quality, pose hazards to aviation and human health, as well as damage ecosystems. The chemical compositions and emission rates of volcanic plumes are also monitored via a range of direct-sampling and remote-sensing instrumentation, in order to gain insights into subterranean processes, in the respect of the magmatic bodies these volatiles exsolve from. Given the significant role these gases play in driving volcanic activity, e.g., via pressurisation, the study of volcanic plumes is proving to be an increasingly fruitful means of improving our understanding of volcanic systems, potentially in concert with observations from geophysics and contributions from fluid dynamical modelling of conduit dynamics. This Special Issue is aimed at presenting the state of the art of the multidisciplinary science concerning all aspects of volcanic plumes, of relevance to the volcanology, climatology, atmospheric science, and remote sensing communities.

Volcanic plumes, made up of material that has explosively erupted from a volcano, are of fundamental importance to volcanology because their deposits record the past activity of a volcano. They also pose a wide range of hazards to humans and can have significant environmental effects. This book integrates observation, theory, and experimental studies and contains recent research ideas and results.

The Physics of Explosive Volcanic Eruptions includes seven review papers that outline our current understanding of several aspects of the physical processes affecting magma during volcanic eruptions. An introductory chapter highlights research areas where our understanding is incomplete, or even completely lacking, and where work needs advancing if our knowledge of volcanic processes is to be substantially improved. The book covers topics on the physical properties of silicic magma, vesiculation processes, conduit flow and fragmentation, gas loss from magmas during eruption, models of volcanic eruption columns, tephra dispersal and pyroclastic density currents.

Volcanoes release gases to the atmosphere both during and between eruptive phases. Primary and secondary processes occurring within the mantle and crust control the gases’ chemical and isotopic compositions as well as their emission rates. Therefore by measuring these gases a wealth of scientific information concerning the source and fate of these fluids is provided. Fluid geochemistry has been highly useful in advancing both our fundamental scientific understanding and procedures for operational volcano monitoring and eruption forecasting. Gases from low-to-high temperature fumaroles and those diffusively released through the soils of volcanic flanks are investigated using various sampling and measurement techniques. Furthermore, a variety of remote sensing methods are applied at relatively great distances from the source to gather major gas composition and flux data for volcanic plumes using ground based, airborne (including UAV) and space borne platforms. The acquired data have advanced science in a number of key ways: • firstly, with parallel thermodynamical modelling to advance our capacity to interpret acquired degassing data; • secondly, through improved constraints on budgets for volcanically mediated geochemical cycling, particularly via regional subduction processes; • thirdly, through improved constraints on the effects of volcanic gases on atmospheric composition, chemistry and radiative transfer, particularly in terms of halogen chemistry, volcanogenic climate change and impacts on human health; • fourthly, there has been a growing body of work focused on combining degassing data with contemporaneous geophysical data and studies on conduit fluid dynamics to advance our understanding of how subterranean gas flow mediates activity at the surface; • and fifthly, there have been considerable advances in the methods themselves, used to make the gas measurements, in particular in terms of extractive sampling (e.g., using MultiGAS units, mass spectrometry, spectroscopic isotope measurement approaches and diffusive denuder sampling) and remote sensing approaches (e.g., DOAS, UV cameras and other imaging techniques, LIDAR and FT)

Volcanic Ash: Hazard Observation presents an introduction followed by four sections, each on a separate topic and each containing chapters from an internationally renowned pool of authors. The introduction provides a volcanological context for ash generation that sets the stage for the development and interpretation of techniques presented in subsequent sections. The book begins with an examination of the methods to characterize ash deposits on the ground, as ash deposits on the ground have generally experienced some atmospheric transport. This section will also cover basic information on ash morphology, density, and refractive index, all parameters required to understand and analyze assumptions made for both in situ measurements and remote sensing ash inversion techniques. Sections two, three, and four focus on methods for observing volcanic ash in the atmosphere using ground-based, airborne, and spaceborne instruments respectively. Throughout the book, the editors showcase not only the interdisciplinary nature of the volcanic ash problem, but also the challenges and rewards of interdisciplinary endeavors. Additionally, by bringing together a broad perspective on volcanic ash studies, the book not only ties together ground-, air-, academic, and applied approaches to the volcanic ash problem, but also engages with other scientific communities interested in particulate transport. - Includes recent case studies highlighting the impact of volcanic ash, making methods used for observation more accessible to the reader - Contains advances in volcanic ash observation that can be used in other remote sensing applications - Presents a cross-disciplinary approach that includes not only methods of tracking and measuring ash in the atmosphere, but also of the fundamental science that supports methodological application and interpretation - Edited by an internationally recognized team with a range of expertise within the field of volcanic ash