Fvof. G. A. J. Cole— Destruction of Chalk. 553 



V. — The Destruction of the Chalk. 



By Grentillb A. J. Cole, M.R.I.A., F.G.S., 



Professor of Geology in the Royal College of Science for Ireland. 



MB. A. C. G. CAMERON, of the Geological Survey of England 

 and Wales, published in 1893 ' an account of a boulder of chalk 

 so large that the village of Catworth has been built upon it, while 

 springs arise between it and the clays which underlie the mass. 

 Sir A. Geikie^ now reports the interesting discovery that "a cake 

 or floor of chalk, lying at the base of the Boulder-clay, may be 

 traced over an area of more than twenty square miles in the west 

 and north of Huntingdonshire and in northern Bedfordshire. It 

 crops out more or less continuously along the brow of the hills 

 under the Boulder-clay and rests on the Oxford Clay. It probably 

 consists of many large sheets of chalk which, at the beginning of 

 the deposit of the Boulder-clay, were transported from the chalk 

 hills lying to the east and north-east." 



Here we are met by the old question which has so often been 

 discussed in presence of the chalk-masses of Cromer. Have we 

 necessarily to do with glacial action on a large scale, or with 

 processes of disintegration which have broken up the Chalk almost 

 in situ ? This massive limestone, traversed by continuous vertical 

 joints, is a ready prey, in our cliflfs and quarries, to undermining 

 influences, and to the flaking 'action of frost. The great rock-falls 

 of Dover or of the Dorset coast would furnish very respectable 

 boulders to any "drift" now forming in the Channel. The famous 

 landslip of Axmouth affected the Chalk to a depth of more than 

 100 feet, and was accompanied by the contortion and upthrust both 

 of the older and more recent strata along the shore. Hence blocks 

 of very various age became mingled together, " invested with sea- 

 weed and corallines, and scattered over with shells and star-fish," ^ 

 representing the existing fauna. Mr. Mellard Reade* has elaborated 

 a combined terrestrial and drift-ice origin for the Cromer boulders ; 

 and, in the discussion on his most suggestive paper. Prof. Hughes 

 compared the phenomena to those of the landslips near Lyme Regis, 

 in the Isle of Sheppey, and along the river Clwyd. 



Chalk resting upon clay along a shore-line is liable to a rapidity 

 of destruction, taking place on an extensive scale, which is nowadays 

 scarcely realized by those who dwell at some distance from the 

 coast. Since catastrophic sea-waves and recurrent deluges have 

 been all but banished from our speculations, it has been the custom 

 to ascribe anything that shows evidence of violence to the glaciers 

 of the Ice Age; and these glaciers have grown in dimensions in 

 proportion to the work ascribed to them. But the storms of the 



^ "Notes on a transported mass of Chalk in the Boulder-clay, at Catworth, in 

 Huntingdonshire" : Glacialists' Magazine, vol. i, p. 96. Also Fortieth Eeport of 

 Department of Science and Art (1893), p. 249. 



^ "Annual Eeport of the Geological Survey and Museum of Practical Geology for 

 1894" : Forty-second Report of Department of Science and Art, p. 274. 



•^ W. D. Conybeare, letter quoted by Lyell, "Principles of Geology," eighth 

 edition, p. 310. 



^ " On the Chalk-masses or Boulders included in the Contorted Drift of Cromer" : 

 Quart. Journ. Geol. Soc, vol. xxxviii (1882), p. 222. 



