Donald B. Dingwell

The 2008 Robert Wilhelm Bunsen Medal is awarded to Donald B. Dingwell for his achievements in the study of the physics and chemistry of silicate melts.

We recommend Prof. Donald B. Dingwell for the Bunsen Medal based on his achievements in the study of silicate melts. Don’s research covers most aspects of the physics of silicate melts. He has made outstanding contribution in the field of silicate melt viscosity. Through an impressive experimental work he explored the roles of temperature and chemical composition on melt viscosity and developed the field of viscometry. He used his results to develop basic understanding of the viscous phenomenon at the atomic level and apply it to models that allow the calculations of the viscosities of a wide range of melt compositions. In addition to studying the effect of the network forming and modifying ions, Don also explored the role of the volatile species on melt viscosity. All these results were applied in numerous papers and serve the volcanological community and the melt scientists alike.

Viscosity is closely related to chemical diffusion and Dingwell made some important contributions to the diffusion of various species in silicate melts. In particular he distinguished between two modes of diffusion, extrinsic diffusion that is related to the mobility of the silicate framework and intrinsic diffusion that related to the ability of an ion or a molecule to move across the silicate framework. He also led the study of halogen diffusion and contributed to the understanding of water diffusion. In order to do this properly, it was necessary to know volatile solubilities in silicate melts and Don contribute to this field as well.

Another phenomenon that is closely-related to viscosity is the glass transition. This is the topic that is most identified with Don Dingwell. His work with Sharon Webb and others on the glass transition and the structural relaxation of silicate melts is a fine example of his ground-breaking science. He was among the first to recognize the importance of the glass transition to geology. He studied the fundamentals of the phenomenon, presented a model that allows both deeper understanding of the underlying physics and practical calculations of relaxation times, and applied the results to studying cooling rates of natural magmas.

Dingwell realized that the structural relaxation of melts is important at the late stages of volcanic eruption and is crucial for understanding the fragmentation of lavas during volcanic eruptions. As he formulated it in his 1996 article in Science magazine this is “A volcanic dilemma: Flow or Blow”. He began studying the properties of volcanic foams and the systematics of their expansion and then developed an experimental device to study fragmentation. Together with Oliver Spieler he studied many natural pumice and lava samples to explore the systematics of fragmentation. Again, in collaboration with geologists on one hand and modelers on the other he pushed for basic understanding of the mechanism and for many volcanological applications of the results.

Dingwell also made important contributions in measurements of thermal expensivity and molar volumes of melts including the development of new experimental technique for their measurements, in element partition between immiscible melts and on trace element solubility in melts.