8s 



MARINE EROSION IN THE WHITBY DISTRICT. 



J. T. SEWELL. 



Lias Shale Cliffs. — The sea wears these away but slowly. 



Oolite Shale Cliffs. — These are more liable to be wasted 

 by the sea's action than are the Lias. Wind and frost are 

 certainly more effective in wearing away these cliffs than is 

 the sea. 



Where the cliff foot or shore is formed of level shales the 

 Lias frequently stands out some yards in front of the perpen- 

 dicular cliff rising- above it ; the sandstones from above as they 

 fall gradually wash into deeper water. 



Clay Cliffs. — The solid blue glacial clay is only slowly 

 wasted by the water, especially when compared with the red 

 boulder-clays. The surface drainage percolates into the 

 vertical cracks formed in the cliffs, and not infrequently brings 

 them down very rapidly. The cause of the subsidence of clay 

 cliffs is either due to the want of surface drainage or to 

 allowing such drainage to run over the cliff face. When once 

 the angle of resistance is formed the sea has little power, 

 especially if the shingle foot is groined. 



Sand and Shingle. — Both sand and shingle appear to be 

 decreasing- in quantity along- this coast, thus giving the waves 

 better access to the cliffs. There are two great causes of sand 

 diminution, ist.: The Tees dredging, which carries the natural 

 river spoil into deep still water, and thus prevents the flood 

 tides depositing it upon our coast ; also this same deep Tees 

 mouth catches the littoral detritus ever washing south along 

 the Durham coast — the waste of cliffs and of rivers, the latter, 

 like the Tees, not having- been dredged until comparatively 

 recent times. 2nd : The other cause that has reduced the amount 

 of shingle on this coast is the stoppage of alum working some 

 40 or 50 years ago. When this trade was flourishing at Boulby, 

 Kettleness, Sandsend, and at Saltwick, an immense quantity of 

 burnt shale and waste earth was shot over the cliff ; the failing 

 of this supply, which had been feeding the sands for 200 years, 

 is now having a marked effect in many of the smaller bays. In 

 Sandsend bay it is probably this cessation of supply, coupled 

 with the lowering of the surface rock by a depth of 6 ft. over 

 a large area outside the Ness point when blasting for jet some 

 30 years ago, that has lowered the sand level some 12 feet and 

 caused the North Riding County Council to build a retaining 



1905 March i. 



