620 SAND-MOVEMENT ON THE NEW SOUTH WALES COAST, 



formed, as there will be no salient points to erode nor indenta- 

 tions to fill up. 



When a coast is in process of rapid subsidence it is character- 

 ised by deep indentations, with rocky headlands and with a fore- 

 shore steep to. When the subsidence is slow the currents and 

 waves have time to erode the shore and convey the resultant 

 shingle and sand to the quiet bays and inlets, to form flats and 

 beaches. Should the geological formation be coarse sandstone or 

 other easily eroded rock, the beaches are quickly formed, the 

 indentations filled up, and the scenery assumes the character ho 

 familiar to the residents near Sydney. When the cliffs and 

 salient points are composed of shale, which, on disintegration, 

 forms a fine mud, we have no sandy beaches, but, except at the 

 head of deep indentations where the mud is deposited to form 

 mangrove flats and marshes, the water is generally deep right up 

 to the shore-line. 



When the subsidence is very slow, or when there is no change 

 in the relative level of sea and land, and there is a good supply 

 of shingle and sand, even the deepest indentations are filled up 

 and islands may be joined to the mainland and form salient points 

 on the coast. There are several instances of this on the coast of 

 New South Wales; the most notable being Cape Hawke, Charlotte 

 Head, Sugar Loaf Point, and Treachery Head and Yacaaba Head 

 at the entrance to Port Stephens. The low-lying sandy country 

 to the west of Cape Hawke is undoubtedly of marine origin, and 

 Wallis Lakes are the only remnants of the large sheet of salt 

 water which originally extended to the foothills of the Dividing 

 Range about eight miles away. 



The sand-reef between the eastern shore of the lakes and the 

 sea beach probably started as a banner reef from Cape Hawke, 

 and as the littoral drift and the prevailing wind both favoured a 

 southerly movement, the reef eventually joined Charlotte Head, 

 South Woody Peak, and then Sugar Loaf Point and Treachery 

 Head. The Myall and Smith's Lakes are not yet filled up, but 

 as time goes on they assuredly will be. 



