Photo credit: Prof. Dave Selby (Durham).

Jon was born in Welwyn Garden City, UK. Having excelled whilst gaining a first class honours degree in Geology from Durham University (Collingwood College) in 1981, Jon undertook a PhD at Leeds University (1981–84) on the petrogenesis of Lesser Antilles arc magmas, which fuelled a life-long interest in volcanology and magmatic processes. Jon moved to the USA where he undertook postdoctoral research at Southern Methodist University and at the University of Michigan, rapidly making a name for himself through his insightful publications and his incisive, common-sense, self-deprecating contributions to international conferences.

In 1988 Jon obtained an academic position at the University of California Los Angeles (UCLA) where he rapidly progressed to full professor. During this time Jon demonstrated his prowess in all aspects of academic practice. His growing body of highly-regarded research publications was complemented by lead authorship of an undergraduate textbook Exploring the Earth: An Introduction to Physical Geology which, typical of Jon, used an innovative layout to engage the reader's attention. His work at this time was recognized through receipt of UCLA's Luckman Distinguished Teaching Award (1994) and the Wager Medal of the International Association of Volcanology and Chemistry of the Earth's Interior (1998).

In 2001 Jon returned to Durham as Chair of Earth Sciences. He served as Head of Department from 2002 to 2005 initiating a period of tremendous reform. Under Jon's leadership the Department revised its entire undergraduate and taught postgraduate curricula, moved into a newly constructed building and developed an entirely new approach to research organization, the benefits of which can be seen in the health and vigour of the research and teaching cultures at Durham today.

Jon's wider contribution to the earth sciences community includes chairing the Volcanic and Magmatic Studies Group (VMSG; 2006–9), chairing the Committee of Heads of University Geoscience Departments (2007–10), membership of a 2014 Research Excellence Framework subpanel (Unit of Assessment 7) and presidency of the Mineralogical Society (2012–13). During this period he also further supported Durham University as Deputy Head of the Faculty of Science (2010–2015) and as a member of Council (2008–2016).

Jon fought a long, hard battle against leukaemia from 2008 until it claimed his life on September 26^th 2016. Jon never let this disease affect his desire to work as is reflected in his receiving the Coke Medal of the Geological Society of London (2011), the VMSG Award (2014), and, in 2016, both Fellowship of the American Geophysical Union and the Distinguished Geologic Career Award from the Mineralogy, Geochemistry, Petrology and Volcanology Division of the Geological Society of America.

Jon was an inspirational teacher and an outstanding researcher who was interested in every aspect of geology. He loved being in the field, whether to teach, learn, or simply enjoy the outdoors, taking every opportunity to visit new locations to broaden his experience of magmatism and the rocks it produces.

Jon will be missed by his many friends for his wisdom, honesty and good-humoured wit. He is survived by his wife Donna and their two children, Max and Daisy.