Plenty River and Anderson's Creek. 161 



The head of this independent stream was probably forked, 

 the prongs representing the small valleys occupied by the two 

 tongues of newer basalt already mentioned. These small 

 valleys had notched the ridge forming the eastern side 

 of the old Plenty valley, the ridge itself probably being 

 reduced by the proximity of two valleys, as commonly 

 occurs. The newer basalt flowing down the old Plenty 

 valley above Morang was, in comparison to the flow to 

 the westward, south of the Morang Hills, cramped for room. 

 It would thus tend to increase in height and bank itself against 

 the bounding ridges. Tracing the eastern edge of the basalt 

 northerly from about l^ miles north of Bundoora to the head 

 of the southern tongue of basalt, the country rises very rapidly. 

 This is shown also by the heights recorded on Quarter Sheet 

 2 S.E. along the Yan Yean Reservoir Pipe Track, where a rise 

 of 100 feet occurs in about a mile (340 feet to 440 feet). At 

 South Morang Railway Station (about 2 miles from the 440 feet 

 level), the height is 512 feet (a rise of 72 feet). Between here 

 and South Yan Yean (3 miles) there is only an increase of 20 

 feet. The easterly tributaries of the old Plenty provided 

 more room here. 



Possibly the greatest check to the flow would be just to 

 the south of Morang, where the basalt coming down the 

 old Plenty valley would meet the main mass from the 

 western side of the Morang Hills; and it is precisely at this 

 point (as the heights above given show) that the greatest amount 

 of ridging up has taken place. This ridging up was sufficiently 

 high to enable the basalt to overflow at the two notches men- 

 tioned above, and to run down as two narrow tongues into the 

 present lower valley of the Plenty ; and thence continue as the 

 narrow strip down such valley. After the basalt flow, the upper 

 Plenty found its way and kept mainly to the junction of the 

 basalt and the older rocks, and so worked its way down as far 

 as Morang. 



If the two tongues of basalt liad not existed, in all 

 probability the course of the river would have continued in a 

 south-westerly direction, between the junction of the main 

 basaltic mass and the older rocks to the east, and would have 

 eventually entered the present Darebin Creek valley below 



