Another very successful Selwyn Symposium and Medal Presentation was held at the University of Melbourne on 29 October 1999. The theme of the symposium 'Geological Catastrophism' was a prelude to the Selwyn Lecture given by Dr Walter Pitman as part of his GSA Public Lecture Tour.

The symposium attracted 73 participants to hear four invited speakers discuss wide ranging aspects of catastrophism. Neil Archbold’s paper "Extinction, Evolution, Catastrophism and Uniformitarianism" examined the anatomy of mass extinctions with particular reference to the end-Premian, the mechanisms that trigger them and the implications of mass extinctions on evolutionary theory. Neil questioned the simplistic view of classical catastrophism and uniformitarianism and quoted authors agreeing with T.H. Huxley that the gradualist view of uniformitarianism may not be correct for it is very conceivable that major catastrophes are part and parcel of uniformity.

Marion Anderson's presentation on "Catastrophic Flooding on Mars" contained brilliant high-resolution images of the Martian surface, which appeared to support theories dating back to the 19th century about the presence of water and flooding on Mars. Landform features and 'outflow channels' on the images show bedforms consistent with high-volume water flow suggesting a catastrophic outpouring of liquid. After reviewing research speculation on likely flooding, the source of water and volume flows, Marion concluded that the majority of researchers still appear to favour the concept of catastrophic flooding on Mars.

Back to earth and Bob Musgrave explained the workings of the earth's outer core and the recent realisation of how complex and chaotic the behaviour of the outer core is. Supercomputer modelling is beginning to show that the earth's magnetic field periodically exhibits a dramatic change when the pattern of frequent polarity reversals stops abruptly and a long interval of constant polarity follows. In his discussion "Catastrophism and the Earths Interior! It's not all Calm under the Surface" Bob suggested that the extinction of polarity reversals is akin to mass extinctions in biostratigraphy and is related to the non-linear chaotic behaviour of the liquid-iron outer core which may have an equally dramatic geological corollary—the formation of mantle plumes and consequent eruption of flood basalts. Finally, Ray Cas concluded proceedings with "The Catastrophism of Volcanic Phenomena: never underestimate the scale and the effects". Of all known geological processes, volcanic phenomena are amongst the most catastrophic and the effects are not always instantaneous but cover a variety of time scales. For those interested the above papers are contained in Geological Society of Australia Abstracts 57 "Geological Catastrophism".

The 1999 Selwyn Medal was presented at the conclusion of the symposium to Dr Bill Birch AM, Curator of mineral, rock and meteorite collections at the Museum of Victoria. The Medal is awarded annually to recognise geoscientific output and significant contribution to Victorian geology.