544 Fisher — Denudations of Norfolk. 



III. — On the Denudations of Norfolk. 



By the Rev. O. Fisher, M.A., F.G.S. 



A Paper prepared at the request of the Local Committee, and read at the Meeting 

 of the British Association at Norwich, 1868. 



AFTER referring to the scope of the subject which had been named by the 

 Local Committee, the Author said — I will first ask your attention to the 

 denudations, by land and sea, now taking place in the county. 



Upon the Lajid Stcrface^ a certain amount of the finer material is being carried 

 into the rivers, and by them deposited at the heads of the broads, or, where such 

 do not exist, in the sea. This denudation by pluvial action is undoubtedly greater 

 where the land is under the plough than it would be otherwise. 



Up07i the Coast, the sea is reducing the solid surface to a uniform level. Where 

 the land is high it cuts away the bottoms of the cliffs, which then founder down, 

 and the fallen matter is in its turn carried oif. Where the land is low, the general 

 contour of the coast is being continued by sand dunes, or (as they are locally 

 called) "marram hills," so that where the lower end of a valley is submerged, as 

 behind Yarmouth, its bottom is being raised seaward, and all reduced to a uniform 

 level and continuous coast line. 



But when the waves have played their part, the action of the sea is not ended. 

 As the waves cut further and further into the land, carrying off, as has been known 

 to be the case, from two to twenty yards during a single storm, ^ the ground thus 

 laid under water becomes subject to the action of the tides, and its surface is con- 

 tinually removed, so as to be kept on the whole at a depth uniform for a given dis- 

 tance from land. If the waste of the shore line is prevented by artificial means, 

 such as sea walls or groins, then the sea is found to deepen more rapidly, and the 

 inclination of the bottom from the shore to be increased. This has notably been 

 the case at Walton-on-the-Naze, in the neighbouring county of Essex. 



Sand and mud are, in the meanwhile, carried by the prevailing winds and currents, 

 and arrange themselves in definite forms, more or less taking the directio!i of the 

 contiguous coast, and shifting, as the shore shifts its position by the destruction of 

 the cliffs. 



If this marine action be considered, it does not appear possible that it can give 

 rise to any very great inequalities of surface, but, on the other hand, that it must 

 tend to reduce those already existing, whether above or below the waters. All 

 great inequalities of the sea bottom must either have been caused by the land having 

 become submerged more rapidly than the sea has had time to erode its coast-line, 

 or else by elevations and depressions taking place beneath the ocean, or in a few 

 instances by powerful currents confined by local circumstances to a narrow 

 course. 2 Nevertheless, since the tides do, in fact, deepen the sea below the level 

 to which the waves act upon the coast, it must follow that the harder rocks will be 

 lowered more slowly than the softer, and shoals be formed. 



Now it is to such a denudation as I have been describing, that we may suppose 

 the form of surface of this county to have been due, at the earliest period to which 

 I desire to call your attention, namely, that preceding the deposition of the Crag. 



The Chalk in Norfolk dips very gently towards the east ; but the inclination is 

 somewhat increased on the western side of the county towards its outcrop,' so 

 that, as seen in a quarry close to the railway station at Hunstanton, it becomes 

 very marked, and amounts to eight or ten degrees. This brings up the Carstone 

 (Neocomian) and the softer clays beneath- The altitude of the Chalk along the 

 watershed of the county is considerable, but has not, I believe, been exactly 

 determined. "VVe may safely then suppose that the sea bottom at the period of the 

 Crag consisted of a shoal bottom of Chalk, nearly level on the eastern side of our 

 area, while the same stratum rose as dry land to a considerable elevation towards 

 its central and western portions; but there is no distinct indication of the position 

 of the ancient coast line of the Crag sea. It certainly extended further inland than 



• For information on this point see Gunn's Geology of Norfolk, in White's History of the 

 Countv. 



* E.g. off the southern point of Norway. 



^ This is a very common case, and usually determines the run of an escarpment. 



