Abstract Volume of the Second International Maar Conference [antikvár]

A tribute to Professor George P. L. Walker Dear Professor, We wholeheartedly dedicate the 2" International lAVCEI/IAS Maar Worlshop to Professor George Walker. George, who is now 78 years old, has made an immense contribution to our understanding of plate tectonics and Iceland geology between 1954 and 1964 and then to our beloved science of volcanology, more directly, starting in 1963. Many of us regard George as the father of modern quantitative physical volcanology. At a time when there were few detailed and systematic studies of volcanic processes and products, and when pyroctastic deposits in particular had received little attention, around the mid-to-iate 1960s, George pioneered such studies. George was in Iceland when Surtsey erupted between 1963 and 1965 and this exceptional phreatomagmatic eruption fascinated him and drew him into volcanology He has worked non-stop on volcanic processes and products ever since. In the last 5 years alone, he has worked, on subjects as diverse as cone-forming eruptions, rift zones and dike complexes, dynamics of lava flow fades formation, new methods of studies of tephra fallout deposits, assessments of tephra fall dispersal data quality, a reassessment of phreatosubpiinian eruptions, the origin of the diversity pyroclast shapes, and more. George promoted quantitative field studies in volcanology and emphasized the need for modeling and laboratory analogue experiments. He would often carry out experiments in the field and in the classroom, making a mess hard to clean up but enlightening his audience about how volcanic processes worked. He helped all these areas of volcanology start In earnest and develop through celebrated collaborative studies with colleagues such as Peter Francis and Lionel Wilson and numerous students whom he inspired including Ian Carmichael, Steve Self, Steve Sparks, John Roobol, Colin Wilson, John Wright and many others. New fields of enquiry including quantitative and process-oriented field volcanology, physical volcanology and volcano sedimentology, planetary volcanology, volcano geomorphology and volcano remote sensing, emerged as a direct result of George's inspiring example. At a time when quantitative studies of pyroclastic deposits were rare, George introduced rigorous methods to recognize them and study them In the field and In the laboratory. This included deposits associated with maar volcanoes such as base surges and ash falls. He also carried out the first detailed studies of littoral cones, documenting that the entrance of some lava flows into the sea can result in highly explosive and hazardous cone-forming eruptions. His studies of the Rabaul eruptions, and of the AD 180 Taupo eruption sequences with Colin Wilson, have become great classics and set new standards in volcanological field work and eruption reconstruction from deposits. This inverse modeling approach, fine-tuned with a few others like Steve Sparks and Lionel Wilson, was successfully applied to hazard assessment at hazardous volcanoes around the world and has enabled to save countless lives at volcanoes (e.g. at Mt Pinatubo). George was particularly Interested In the phreatomagmatic phases of the Taupo or Rabaul eruptions and he was the first to point out that volcanological and meteorological processes can interact and to document how this affected the deposit features. Not surprisingly this Is now starting to be recognized as one of the most exciting contemporary areas of volcanology. Of course, George's interest in monogenetic volcanoes and basaltic volcanism generally Is also well known. During his 15 years as Gordon Macdonald Professor of Volcanology at the University of Hawaii (1981-1996), George spent much of his time mapping the Hawaiian volcanic systems. He was able to do this thanks to the realization that the different Hawaiian Islands had formed In a similar way but were at different stages of erosion. He carried out systematic field work for many years on these volcanoes, integrated all the data, and was able to shed new light on the 3D structure and time-evolution of basaltic systems like those in Hawaii. His work on rift zones and dike complexes, notably in Iceland and Hawaii, remains the best to date. Asked if he would write a few words to inspire this conference a few weeks ago, George told us that there were plenty of good reasons for studying monogenetic fields and especially maar volcanoes and their deposits. He noted that of course any work that would enable to avoid another Lake Nyos-like disaster would be most welcome, but he said that an overwhelming reason for studying maars and monogenetic fields is that "they are there". How could we not study them? One will recognize in this statement that scientists are often driven by a simple and powerful urge to describe the natural world and by an irresistible curiosity and need to understand how the Earth works. George is delighted that the workshop is taking place and that once again it will be attended by such a diversity of scientists, covering all the aspects of volcanology that he promoted including several that he helped pioneer George has always championed quantitative and process-oriented field and laboratory work and no doubt he would have taken special delight in attending those talks and posters presenting an abundance of new field and laboratory data, and in those modeling presentations informed by such field and laboratory constraints.