Art. X.—The Bluff at Bariuon Heads. 



(Witli Plate XIV.) 



By G. S. Griffiths, F.G.S. 



[Read November 6, 1891.] 



This bold headland, at the uioutli of the Riv^er Barwon, 

 presents some features of geological interest. A crag of 

 grey sandstone, it owes its preservation to the circumstance 

 that its seaward extremity stands upon a basement of hard 

 lava, which rises just above the level of high-water. The 

 result of such an arrangement of the rocks is illnstrated bj- 

 the profiles of two of the cliffs, one of which consists wholly 

 of calcareous sandstone, the lava foundation being wanting. 



Where the base is of lava, as it is in the cliff at B in 

 Section A B, the profile has an inclination of about 45°, and 

 can easily be scaled. This shows that the rate of recession 

 of the face of the cliff is much faster than that of the foot. 

 Now, the foot of such cliffs is cut back b}^ both the sea and 

 the weather, while the face is cut back by the weather alone. 

 As the waves and weather together work into the cliff much 

 more quickly than the unaided atmospheric agencies can, we 

 seek for some special condition in the cliff itself, to explain 

 the slanting profile, and we find it in the toughness of the 

 lava base, which here retards the encroachments of the 

 waves. 



If we now turn to the cliffs near D, we see that one is 

 vertical, and another, which I have not drawn, is deeply 

 undercut at the sea level, so that it continually falls in great 

 slabs, which encumber the beach. Here the entire face of 

 the cliff is of homogeneous material, and the greater wasting 

 jiower of the sea over the atmosphere shows itself in the 

 profile, which is vertical where it does not overhang its foot. 

 The aerial destruction is not less here, but the sea scour is 

 much greatei'. Hence the difference between the profiles of 

 the two cliffs. 



K 2 



