IAVCEI Proceedings in Volcanology – serie

The contributions in this book were presented, orally or as posters, at the International Volcanological Congress held in New Zealand from 1 to 9 February 1986, the centenary year of the Tarawera eruption of 10 June 1886. More than 500 people, from 29 countries, attend­ ed the Congress. Most of these works formed part of Symposium 4, "Volcanic Hazards - Prediction and Assess­ ment", convened by J.H. Latter, R.R. Dibble, D.A. Swanson and C.G. Newhall. The collection represents over half of the published abstracts of Symposium 4, together with three papers given at the Symposium, which lacked abstracts, and two which were part of Symposium 1 on pyroclastic flow deposits. The contribu­ tions cover a good proportion of the volcanically active parts of the world, with Italy, Japan, the West Indies and the USA especially well represented. Mount Erebus, Vulcano and Rabaul are individual volcanoes which have been treated in particular detail. Unfor­ tunately, there are no chapters in the book dealing with Africa, the Atlantic islands (except Iceland), Hawaii, Central America (except Mexico), or South America (in spite of the major disaster at Nevado del Ruiz Volcano in 1985).

This collection of papers is based on a symposium held in 1987 at the Interna­ tional Union of Geology and Geodesy Congress in Vancouver, British Colum­ bia. The Symposium was planned as a follow-up to a session at the 1984 Geo­ logical Society of America Annual Meeting in Reno, Nevada, which dealt with the emplacement of silicic lava domes. In both cases, emphasis was placed on the physical and mechanical rather than chemical aspects of lava flow. The IUGG Symposium consisted of two lecture sessions, a poster session, and two discussion periods, and had 22 participants. The contributions to this volume are all based on papers presented in the various parts of the Sym­ posium. The motivation for studying lava flow mechanics is both practical and scientific. Scientists and government agencies seek to more effectively predict the hazards associated with active lavas. Recovering mineral resources found in lava flows and domes also requires an understanding of their emplacement. From a more theoretical standpoint, petrologists view lava studies as a way to directly observe the rheologic consequences of mixing crystals, bubbles, and solid blocks of country rock with silicate liquids. This information can then be used to constrain processes occurring in the concealed conduits, dikes, and chambers that feed flows and domes on the surface.

For many centuries people living on volcanoes have known that the outset of seismic activity is often a forerunner of a volcanic eruption. This understand­ ing allowed people living close to the sites of the Mt. Nuovo 1538 eruption at Campi Flegrei, Italy, and of the Mt. Usu 1663 eruption, in Hokkaido, Japan (to quote only two examples) to flee before the eruptions started. During the second half of the 19th century seismographs were installed on some volcanoes, and the link between seismic and eruptive activity started to be assessed on a firmer scientific basis. The first systematic observations of the correlations existing between seismic activity and volcanic eruptions were probably those carried out at Mt. Vesuvius by Luigi Palmieri in 1856. Palmieri was the Director of Osservatorio Vesuviano and built an electromagnetic seismograph with the aim of "making visible the smallest ground motions by recording them on paper and indicating direction, intensity and duration". He was able to show the relationship between earthquakes and the different phases of volcanic activity. He identified the harmonic tremor which he indicated was a precursor of volcanic activity: "the characteristic feature of the ground mo­ tions preceding eruption is its continuity . . . (before the eruption of 1861) the electromagnetic seismograph began to show a continuous tremor". The Palmieri seismograph was also utilized in Japan until 1883, when it was replaced by the new Gray-Milne seismographs, and, later, by the Omori in­ struments.