32 
MORTIMER: ORIGIN OF CHALK DALES 
As early as 1873, 1 expressed my opinion in a paper which I read 
to the Members of the " Driffield Literary and Scientific Society," 
that nearly all the valleys on the chalk wolds of Yorkshire, were due 
in the first instance and in a great measure, to cracks or fissures 
caused by the elevation of the bed of chalk into dry land, and that 
since the commencement of that elevation, those gaping cracks have 
been widened and acted upon by submarine subaerial, and all the 
denuding and abradmg forces of natiure ; some of which are slowly 
at work now. The following is an extract from the paper I read 
in 1873. 
" There is little doubt that the chalk was originally deposited 
**at the bottom of the cretaceous sea, horizontally or nearly so, and 
" probably in somewhat extensive areas, and that about the close of 
" the chalk formation, or sometime after, an upward motion, probably 
" due to a lateral thrust, took place, and consequently, as there is 
" but little elasticity in a piece of chalk, the whole mass began to 
" suffer rents and fissures in every direction. As the upheaval 
" proceeded these fissures w^ould widen and lengthen until the 
" upward motion ceased. Since then, subaerial and submarine forces 
" have assisted to produce the present smooth appearance of these 
valleys." 
As early as 1873, observations in the field had forced upon 
me these views, and since then they have been strengthened by 
repeated examination and study. I wish it to be clearly understood 
that my views and remarks in this paper are confined entirely to the 
chalk area of Yorkshire. I fully admit that many valleys formed 
entirely by erosion do exist on many parts of the earth's surface, and 
to a gTeater or less degree exist almost everywhere. But, because 
we find in one place a series of valleys which have clearly been cut 
out by river action, we must not overlook the fact that a somewhat 
similar series of valleys may have been excavated in other places by 
other forces. 
The accompanying section. No. 1, gives very strong evidence 
of the chalk-dales being the result of extensive dislocations, arising 
probably, as before mentioned, from lateral pressure. This section 
extends in nearly a straight line from Hanging Grimston, a point at 
