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George Patrick Leonard Walker, 1926-2005

George Walker was one of Britain’s most outstanding geologists of the last few decades and one of the world’s most influential volcanologists. He obtained his BSc Honours and Master of Science degrees at Queens University, Belfast, and completed his training with a PhD in mineralogy at Leeds University (1956). By then he had already been appointed to a lectureship at Imperial College, London.

George’s earliest scientific achievements were in the field of mineralogy when he recognised and mapped secondary zeolites mineral zones in the basaltic lava flows of northeastern Ireland. This resulted in a classic series of papers on the burial and alteration of flood basalt lavas published between 1951 and 1960. Later, in the 1960s, he turned his interests to the lavas of Eastern Iceland. From mineral zones in Icelandic lavas, he went on to discover welded ash deposits between the lavas, to describe whole volcanic centers, and to be one of the first to investigate sub-glacial volcanic deposits. His work included several ground-breaking insights, including contributing to the growing picture of plate tectonics by showing how dyke swarms in Eastern Iceland were produced during crustal spreading. This research revolutionised the understanding of Icelandic geology and in 1980 he was one of the rare foreign citizens to be awarded the Order of the Falcon, conferred by the President of Iceland. During this period also began studies on the rheology of lavas from Mt. Etna and was the first to show a relationship between effusion rate and lava flow length.

Around 1968 George began to expand his interests to explosive volcanism. His papers on pyroclastic rocks, which form the fundamentals of modern quantitative volcanology, are numerous. During one decade, beginning in 1971, he essentially revolutionised the standard approach to studying and understanding explosive volcanism, turning it from a qualitative and descriptive enterprise to a quantitative science.

George left Imperial College in 1978, having been a Reader there since 1964, and took up a Captain James Cook Research Fellowship of the Royal Society of New Zealand based at the University of Auckland, from where he began his work on the young Taupo Zone volcanic rocks. This period led to many new concepts, including low aspect-ratio ignimbrites, deposits of particularly violent eruptions that (thankfully) do not occur very often. He also uncovered evidence for ultraplinian eruptions, this planet’s most explosive volcanic events. In 1981 he accepted the Macdonald Chair in Volcanology at the University of Hawaii, and during that decade his interests turned towards lava-producing volcanoes once again. He focused on the evolution of basaltic volcanoes and the dynamics of basalt lava flow and dyke emplacement, and included AMS palaeomagnetic studies to reveal flow and inflation processes. George retired from Hawaii in 1996 and returned to the UK to live in Gloucester, when he held an Honorary Professorship at the University of Bristol.

The achievements of George’s career were recognised by many awards, including election as Fellow of the Royal Society in 1975, an Honorary Doctorate at the University of Iceland, an Honorary Fellowship of the Royal Society of New Zealand, the Thorarinsson medal from the International Association of Volcanology and Chemistry of the Earth’s Interior (the highest award in volcanology), and the Wollaston Medal of the Geological Society of London.

George was a brilliant teacher and devoted much of his time to encouraging and nurturing young scientists. As an expert field geologist, there was nothing he liked better than showing students how to read the rocks on field classes or training postgraduate students how to extract the secrets of nature by simple systematic observations and logical deduction. In Hawaii he spent a considerable amount of time at schools talking about geology and volcanoes, and leading field trips for many non-specialist groups. He inspired thousands of people from primary school children to undergraduates, from to PhD students to eminent professors. Possibly his most influential, long-term contribution, other than his own writings on volcanology, will be the collaboration with, and training of, other scientists. Many now-distinguished volcanologists and petrologists studied with George, and also helped and encouraged many scientists from the developing world, where most active volcanoes are located.

George Walker was a quiet man who never sought the limelight. He was at his happiest in the field in remote parts of the world making observations that changed our understanding of volcanoes forever. His contributions to science were seminal and he will be remembered with admiration for his genius and great affection by everyone who crossed his path. George was a devoted husband and father, and leaves his wife Hazel, daughter Alison, son Leonard, and grandson Matthew. He was born on 2 March 1926, and died on 17 January 2005.

Stephen Self