FROM MAGMA TO TEPHRA (Developments in Volcanology)
Editorial Reviews
Review
(S. Self)
...Those who want a timely summary of much widely disseminated work will find it invaluable... It is a very good addition to the volcanological literature and the editors are to be commended.
Journal of Volcanology and Geothermal Research
(R. Carniel)
...gives the reader access to the status of research and modelling in a series of fields of volcanology that literally accompany him/her from the dynamics of magma vesiculation and fragmentation to the deposits of explosive eruptions. ...this is a most valuable book ... advanced students but also (or especially) professional volcanologists and researchers will find in a single book an impressive amount of high standard and updated information about the topics covered by the book, together with a conspicuous number of relevant references to the literature published in the past and especially in the very last years.
Volcano Quarterly Online
(J.C. Tanguy)
Cet ouvrage constitue une mise au point et un recueil de données quantitatives fondamentales pour chercheurs et étudiants de haut niveau.
Geochronique
(C. Oppenheimer)
Almost twenty years ago, at 08:32 Pacific Daylight Time on the 18th May, 1980, a magnitude 5.1 earthquake triggered an explosive eruption of Mount St. Helens which, in turn, triggered huge interest in the physics of volcanic processes. More recently, the pace has, if anything, accelerated thanks to the motivation provided by further well-studied eruptions, including Pinatubo (Philippines) in 1991, and Soufriere Hills volcano (Montserrat) in 1995–1999. An impressive body of literature has accumulated just in the past decade spanning empirical, theoretical and observational approaches; physical models have been tested, validated and compared using laboratory experiments and remote sensing observations of real eruptions. Much of this recent research has focused on experimental and theoretical treatments of micro-scale processes and scaling issues – for example, how inter-grain interactions influence transport of, and sedimentation from, pyroclastic density currents, and how the mechanisms of bubble nucleation and transport in silicate melts ultimately influence eruption styles. These results greatly flesh out the first-order eruption physics that had been elucidated through research in the 1970¿s and 1980¿s. In addition, actual eruption deposits have been scrutinised in increasingly detailed and diverse ways supporting the development of techniques for inversion of the tephrastratigraphic record to infer eruption styles.
These developments have enormous implications for volcanic hazards assessment because eruption prediction based solely on empirical pattern recognition (e.g., from seismicity or ground deformation records) is often hampered by the limited periods of monitoring conducted prior to volcanic eruptions. All too often, surveillance networks are only installed after a volcano has shown obvious signs of unrest such that instrumental data are collected once the system is already in an abnormal state. This makes it difficult to judge what "baseline" seismicity, gas emission, ground deformation, etc., are and, hence, what constitutes a significant excursion in one or more observed parameters. For this reason, understanding the physical and chemical processes that control eruptions is crucial in that it enables interpretation of phenomenological data with respect to theoretically- based or experimentally tested models. Likewise, definition of hazard zones around a volcano – a crucial aspect of hazards mitigation – depends on a thorough appreciation of the physical factors that dictate the run-out of pyroclastic density currents and lava flows, the fallout of tephra, etc. Such considerations of the physics of eruptions have been highly prominent in the scientific approach to management of the Montserrat crisis, for example.
Freundt and Rosi¿s text brings together eight distinguished authors to cover the fundamental physical processes underpinning explosive volcanism. The title and organisation of chapters broadly reflect the evolution of a volcanic eruption – beginning with the de-volatilisation and fragmentation of magma (Dingwell on the physico-chemical processes involved in bubble nucleation and growth through to the fragmentation of magma; Zimanowski on magma–water interaction and the causes and consequences of phreatomagmatic explosions), its flow through a conduit towards the Earth¿s surface (Papale on transport equations and degassing-rheology feed-backs),the ascent of the eruption column into the atmosphere (Valentine on governing equations, buoyant vs. collapsing columns, and consequences of atmospheric structure), and the fallout (Rosi on clast dispersal, and modelling of eruption parameters from grain size and thickness characteristics) or flow (Freundt and Bursik on experimental and theoretical treatments of pyroclastic flows and deposit facies, and Wohletz on pyroclastic surges) of pyroclastic material on to, and beyond, the flanks of a volcano.
The chapters are of a uniformly high standard, and provide essential introductions to substantive topics in volcano physics - they synthesise hundreds of journal papers, many of them only published in the last few years. The book will be an important reference source for volcanologists from post-graduate level up. Ultimately, unified models should be achievable that link magma chamber processes to conduit flow to transport through the Earth's atmosphere, or across the surface, and sedimentation of tephra. The advanced state of the art reported in this book suggest that such models may not be so far off.
Clive Oppenheimer, Department of Geography, Downing Place, Cambridge, UK
Earth-Science Reviews, 49
Book Description
Hot magma rising through the Earth's crust releases gases that expand and may come into contact with external water that vaporizes. The magma is then fragmented into an accelerating gas-particle/droplet mixture that is shot into the atmosphere, possibly in an overpressured state, where it may buoyantly rise up into the stratosphere as an ash plume, partially or totally collapse back to the surface, or rapidly expand sideways, or undergo a combination of these processes. Tephra is then deposited on the Earth's surface by pyroclastic fall, flow or surge, or some hybrid mechanism. The combination of processes that operate from the degassing of magma to the emplacement of tephra makes an explosive volcanic eruption, and the physical characterization of these processes is the scope of this book.
In this book we summarize the insights into key aspects of explosive volcanic eruptions gained from physical modelling to date.
The seven chapters are arranged in an order reflecting the sequence from processes acting within the volcanic
conduit through dynamics of eruption and transport through the atmosphere to mechanisms of emplacement on the Earth's surface.
Chapter 1 reviews the progress made in understanding how magma vesiculates and fragments, considering results obtained by experiment, theory, and analysis of the vesicle-texture of pumice. Magmatic fragmentation is discussed in terms of brittle failure as tensile strength is exceeded by internal and/or external stresses. The explosive fragmentation of hot magma upon contact to external water is experimentally shown in Chapter 2, emphasizing the need for water-entrapment configurations to cause explosive interaction during which extremely high stresses fracture melt in a brittle fashion. The motion through the conduit of vesiculating magma below the fragmentation level, and of the gas-particle/droplet mixture above fragmentation is investigated in Chapter 3. Pressure evolution along the conduit and exit velocity at the vent are shown to
vary with initial magma chamber pressure, magma composition, and composition of the mixed H
Chapter 5, showing how deposit characteristics can be used to estimate eruption parameters such as discharge rate and column height. The generation, transport and emplacement of pyroclastic flows is discussed in Chapter 6, reviewing the presently much debated transport concepts ranging from grain flow through fluidized flow to suspension currents,
and elaborating the suspension-current model thought to be applicable to widespread ignimbrites. Finally, Chapter 7 summarizes observations from nuclear explosions and characteristics of pyroclastic surge deposits as a basis to then theoretically analyze the compressible two-phase flow of both dry and wet pyroclastic surges.
FROM MAGMA TO TEPHRA (Developments in Volcanology),A. Freundt,M. Rosi,Elsevier Science,0444507086,Earth Sciences - Geology,Science,Science/Mathematics,Volcanology,Science / Geology,Vulcanology & seismology
Books Review:
Recommended Books