Volcanic landforms and deposits found across Central and Western Victoria, together with related areas in SE South Australia, form the Newer Volcanic Province of SE Australia (Figure 1). Some 400 volcanoes are known, and lava, scoria and ash cover approximately 15,000 sq. km. Absolute dating, supported by some stratigraphic evidence, indicates activity began some 7 Ma ago, and the most recent activity at Mt Gambier in South Australia was about 5,000 years ago. A major part of the activity occurred during the Quaternary, including during occupation of the area by aboriginal people, and future activity cannot be ruled out.

An M.Sc. study of the Geelong area by Jim Bowler, completed in 1963, was mainly concerned with the Tertiary sediments of the area, but also discussed Tertiary and Quaternary sequences, including basaltic lava flows, weathering of sediment and basalt, and the physiography of the Geelong area. The Moorabool Viaduct Sand, a calcareous sand and calcarenite of late-Miocene to Pliocene age, is an important marker for post-Quaternary volcanics. Originally defined in the Geelong area by Bowler (1963) as the sediments between the Fyansford Formation and the overlying Newer Volcanics, its ferruginous weathering and silicification clearly show the influence of late-Tertiary climate. Bowler also recognised evidence for young tectonic activity during and since the time of volcanic activity, evidence of importance in current neotectonic studies in Victoria.

Across Victoria and SE South Australia Quaternary volcanism has left well-preserved cones, craters and crater lakes, scoria with irridescence and stony rise lava flows with ropy and glassy surface textures, and such an obvious youthful appearance overall that the explorer Major Mitchell, the first person to recognise the area as volcanic in 1836, suggested that eruption had been "within the memory of man". However, the thin and widely-separated flow and ash deposits mean volcanic stratigraphic correlation is difficult, and occasional interfingering of these deposits with equally thin and discontinuous Quaternary sediments provides little help with broad correlation across the area.

Further dating, including a new program of Uranium series dating with Ken Collerson and Ph.D. student David Murphy of the University of Queensland, should help clarify the age of activity during the last 0.5 to 1 Ma. Current regolith landform mapping, based largely on radiometric imagery acquired by the GSV in the last few years, and incorporating many detailed student maps of individual volcanoes and deposits, provides a good idea of activity during the last 2 Ma or more (see Joyce 1999). From this work a new estimate of the number, type and distribution of the Quaternary volcanoes and their deposits can now be made, and it is clear they are a major feature of the Quaternary for this part of the Australian continent.

The chronosequence of regolith, landforms and drainage on the Newer Volcanic lava flows of Western Victoria also provides an excellent setting in which to study climate and climatic change, and especially a major change ~2.5 to 3 Ma. Late-Tertiary active weathering and iron movement has produced on lavas deep pallid kaolinitic profiles with ferruginous and mottled upper zones, and these contrast with the slow rate of soil formation since that time which has produced clay soils only 1 to 2 m deep (Figure 2).

Volcanism in Victoria is both an aspect of the Quaternary, and also a key to its further study. It is a major aspect of the landscape, dramatically affecting drainage, groundwater, landforms and soils, and so influencing plants and animals, and aboriginal and later settlers, who have inherited and used a volcanic landscape overprinted with the effects of Quaternary climates. Volcanism is a key to future Quaternary studies which will use volcanic deposits and landforms as age markers, as traps for sediment, fossil pollen and other aeolian deposits, and as sources of archaeological materials for hand axes, and construction such as eel traps and houses. Most recently interest in neotectonics has begun to demonstrate that faulting, warping and doming is a young and probably continuing aspect of the region, affecting the landscape generally but also related to the difficult problem of when volcanism occurred, and why it has occurred in certain areas and not others.

Future work should include studies of the interaction of aeolian and volcanic deposition, particularly in soil formation, and of possible cycles and climaxes in past volcanic activity, and their relevance to predictions of future activity. It is also important to be able to describe the physical effects on the landscape of a scoria cone–lava flow eruption, or a more explosive maar eruption, both to help understand the Quaternary landscape, but also to consider the likely effects of any future activity.