Lava Residuals, 161 



(4) Newer Basalt Cycle. 

 Short lived cycles between successive flows of newer Icivas. 



(5) Post Newer Basalt Cycle. 



POET PHILLIP SYSTEM. 



Lateral Valleys — 



Yarra, between Heyington and 



Fairfield. 

 Merri Creek (part), 

 Darebin Creek (part). 

 Moonee Ponds Creek (part). 

 Saltwater River. 

 Eiddell's Creek. 

 Hovel's Creek (part). 



Valleys formed on Extensive Lava 

 Field— 



Kororoit Creek. 

 Werribee Eiver. 

 Skeleton Water Holes. 



Synopsis of Paper. 



The lava residual is the result of the greater resistance to erosion 

 of basaltic lavas compared to that on the softer rocks, contiguous to 

 them. 



The development of the Older Basalt residual is characterised by 

 three readily defined cycles — namely, (1) the Pre-Older Basalt 

 cycle, (2) the Older Basalt cycle, and (3) the Intermediate cycle. 

 The development of the Newer Basalt residual is also characterised 

 by three cycles — (3) the Intermediate cycle, (4) the Newer Basalt 

 cycle, and (5) the Post Newer Basalt cycle. 



The Intermediate and Post Newer Basalt cycles during which the 

 actual development of the residuals took place were, at their incep- 

 tion, characterised by two types of lava field, formed during the 

 preceding cycle, namely — (a) the confined lava field which was con- 

 tained within the watersheds of the Intermediate cycles, and (b) the 

 extensive lava field Avhere the lava escaped the limits of these water- 

 sheds. 



The development of a residual from a confined or extensive lava, 

 field proceeded, at its initial stages, on somewhat different lines. 

 From a confined lava field, a residual was developed by lateral 

 streams on the soft rocks at tlie parallel edges of the lava ; from an 

 extensive lava field, the development was by lateral streams on the 



