Physiography of Werribee Area, 217 



Physiographic evidence. — The line of the scarp is almost 

 .•straight, but, as shown on Fig. 5, is slightly concave to Port 

 Phillip Bay. The general height of the scarp is considerable. The 

 levels, indicated by 100 foot contours, as shown in Fig. 6, are 

 ■copied, by permission, from the Ballan and Meredith Sheets of the 

 Military Survey. These plans give the most exact interpretation 

 possible of the line of the fault, based on geological and physio- 

 graphic evidence, confirmed in the field. Smaller contour intervals 

 greatly emphasise the scarp. 



One may approach the scarp in a direction normal to it at any 

 part from the east, and travel twenty to thirty miles from sea level 

 to reach an average elevation of 500 feet at the base of the scarp, a 

 mean grade of 20 feet to the mile. Continuing in the same line, 

 the next mile of progress would carry us up to over 1300 feet, a 

 grade of 800 feet to the mile. Once on the plateau, we may proceed 

 westw^ard another twenty miles at a mean elevation of 1500 feet, 

 an average rise of ten feet to the mile. (See Fig. 12). 



The height of the scarp is greatest towards the northern part 

 ■^( about 900 feet), where it bounds the eastern face of the Lerderderg 

 Ranges. It is best demonstrated along the fifteen miles running 

 south from the Parwan area (average height here 800 feet), and is 

 least pronounced at Bacchus Marsh (about 300 feet), and at the 

 southern end, near the junction of the east and west branches of 

 Sutherland's Creek (about 200 feet). Scaled sections across the 

 scarp at various points are included in the portion of this paper 

 that deals with the geological evidence. 



The effect of the scarp has naturally been to give the established 

 rivers on the higher block greater eroding powers. On the lower 

 block the rivers all flow at even grades across the plains, while 

 .above the scarp deep precipitous gorges are the rule, especially 

 in the hard Ordovician slates and sandstones. The Lerderderg 

 gorge, at the point where that river crosses the fault, is nearly 1000 

 feet deep. The Werribee Gorge, one of the best-known scenic 

 features in the area, is much more precipitous than that of the 

 Lerderderg, and is up to 800 feet deep. Still further south, the 

 ''Anakie Gorge," on a tributary of the Little River, is about 700 

 feet deep where it crosses the fault. In all cases the rivers immedi- 

 ately pass, on leaving the gorges of the liiglier block, to shallow 

 channels cut into alluvial material. 



The multitude of minor streams which seam the scarp face, 

 heading back at high grades into, the higher block, closely approxi- 

 :mate, in the nature of their valleys and spurs, to those outlined by 



