Plenty River and Andersons Creek. 165 



If the Plenty were captured at the Barber's Creek Gap before 

 the flow of the newer basalt, its upper waters would be diverted 

 into the old Merri Creek basin, but the original valley south- 

 west of Morang would remain, carrying an independent stream 

 until the newer basalt eruptions. 



The Relations of the Plenty and Yarra Rivers. 



The old Plenty gives evidence of having been fairly well 

 developed before the flow of the newer basalt ; and from the 

 width of the old Merri Creek valley, the same may be said of 

 thai. (From the geological maps, it seems probable that the 

 old Merri Creek was joined by the old Moonee Ponds Creek). 

 The Yarra for some distance above Templestowe has all the 

 characters of a youthful valley, as Prof. Gregory has pointed 

 out.i Between Templestowe and the mouth of the Darebin 

 Creek, the river meanders through its own alluvium. Dr. Hall^ 

 has remarked that the newer basalt (down the Darebin Creek 

 valley) checked the flow of the river above the Fairfield railway 

 bridge, the effect of which was to build up a plain of sediment 

 up the Yarra as far as Templestow^e, and up the Plenty, where, 

 a mile above its junction with the Y^arra, the alluvium is 30 

 feet deep. The checking of this body of water would also cause 

 the river to meander and so to widen its valley. It has simi- 

 larly atfected the Koonung Koonung Creek, although this is not 

 shown on the geological maps. The effect of the basalt bar at Fair- 

 field extends to the Plenty, and up that stream to some extent. As 

 mentioned above, the upper Plenty waters were diverted at 

 Morang by the newer basalt floAv into the present Plenty 

 channel. Hence practically at the same time the Yarra was 

 checked at Fairfield, and a large additional volume of water 

 from the upper Plenty basin was poured into the Yarra through 

 the present Plenty mouth. This water, without the bar at 

 Fairfield, would tend to widen the stream below its entry (if 

 the stream were at or near its grade), and tend to a somewhat 

 sharp disparity between the nature of the valley above and 

 below the mouth of the present Plenty. It would be accentuated 

 by the basalt at Fairfield, and in this way the existing condi- 

 tions have arisen. The limitation of the alluvial flats up 



1 lb., pp. 106 and 107. 



•2 Victorian Hill and Dale (1009), p. 42. 



