185 



aboriginal legends, it may be mentioned, that in the recorded 

 legends of the Mount Gambier tribes there is frequent refer- 

 ence to the lakes, etc., of the district, but nothing that I 

 have read to suggest that the race had any record of an 

 actual eruption. 



Summing up this evidence, we may conclude that Mount 

 Gambier and its associated vents represent a western mar- 

 ginal outburst from the great basaltic magma that gave rise 

 to the Victorian Newer Basalts, occurring near the close of 

 the Newer Basalt Period, and possibly dating to quite late 

 pre-historic time. 



7. Duration of the Eruptive and Effusive Phases. 



As pointed out by previous observers, the preliminary 

 phase of the Mount Gambier volcano was an explosive one, 

 brief in duration, as evidenced by the thin layer of ash to 

 be seen immediately overlying the Janjukian Limestones,, 

 and. underlying the basalt flow. 



Following this, the lava welled up and flowed for a couple 

 of miles or so in an easterly direction. There is no evidence 

 to suggest that the lava belonged to a later stage of activity 

 and was forced along in its present position as a "sill." The 

 effusive phase, like the other features of this volcano, was 

 on a diminutive scale, and lasted probably for a few hours 

 only. 



Subsequently the volcanic activity was wholly explosive,, 

 at times with considerable violence. In the effort to discover 

 the probable duration of the building of the cinder cones, 

 investigation has been made of all available descriptions of 

 cases where the duration of activity is known, either actually 

 or approximately. The best comparison might be made with 

 the well-known case of Monte Nuova, near the Bay of Naples, 

 since that particular cone, though smaller, is comparable to 

 the chief cone at Mount Gambier in height and circumfer- 

 ence. It will be remembered that, about 400 years ago, 

 Monte Nuova was built up before the eyes of observers in. 

 a few days. 



Mount Gambier is larger and. more complex in structure, 

 but it is clearly possible that its volcanic history was very 

 brief. As already mentioned, effort was made to discover 

 evidence regarding the duration of activity from comparison 

 of the graphic records of present-day wind direction with the 

 distribution of the ash. The evidence is admittedly of no 

 high value, but, taken for what it is worth, it suggests that 

 the cones were built up in the later months of the year. 



It has been pointed out that cinder cones, in some cases, 

 preserve their shape in a remarkable manner. This is 



G 



