GEOFF BROWN, the vulcanologist, was one of two British delegates at a workshop in Colombia designed to establish a comprehensive geophysical and geochemical monitoring programme at Galeras volcano, Colombia.The meeting was funded by the US National Science Foundation, and Galeras had been identified as one of the most important volcanoes to study in this International Decade of Natural Disaster Reduction because of its high level of activity and proximity to large towns such as Pasto. Brown was killed when the cone inside the crater erupted, sending rock fragments hundreds of metres into the air at over 1,000C.Brown was an active and productive researcher in several fields, from experimental studies on granites, to geothermal energy evaluation, to physical vulcanology. I worked closely with him on the latter project over the last 10 years developing techniques, first to map out the sub-surface structure of active volcanoes and then to monitor and model changes within them. The objective of the research is to understand how volcanoes work and what processes operate within them before and during eruption. We use gravity and ground deformation measurements to do this and it was while setting up a network of observations within the active crater of Galeras volcano that Brown was killed. His untimely death is a tremendous loss to vulcanology - his insight into the relationships between geophysics, geochemistry and geology and their applications inspired his colleagues and enthused every one he met.Vulcanology was only one aspect of Brown's busy life. He had been the Head of the Earth Sciences department at the Open University since 1983, responsible for teaching the equivalent of 1,000 undergraduate students. A gifted teacher and communicator, he wrote several undergraduate teaching texts and presented television and radio programmes both for the OU and BBC, including a Horizon documentary. He also co- authored and co-edited respectively the much praised textbooks Understanding the Earth and The Inaccessible Earth. As if this was not enough, he somehow found time to chair the Research Committee, co-ordinating research enterprises throughout the Open University.Brown's philosophy of life was to live to the full and he threw himself wholeheartedly into everything he did. The University Grants Council identified his department as one of the top seven in the UK in 1989, but the unique funding of the Open University meant that no funds for further expansion were forthcoming. He therefore actively sought external and internal monies and a new laboratory wing partly funded by the Wolfson Foundation was opened by the Secretary of State for the Environment yesterday. This is the first building on the campus to be financed in this way and to be devoted entirely to research activities; it is tragic that Geoff Brown, who worked so hard for this moment, was not there in person.