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Meanwhile, Kingsdale Beck (if it exists) has run<br />
along its straightened course to be replenished at Keld<br />
Head, where <strong>the</strong> becks that disappear into <strong>the</strong> potholes reemerge.<br />
At Keld Head <strong>the</strong> waters meet <strong>the</strong> impermeable<br />
Silurian rocks that underlie <strong>the</strong> limestone and form a<br />
huge underwater cavern. At first glance, it seems that<br />
Kingsdale is enclosed on all four sides by higher ground,<br />
with Raven Ray forming a barrier to <strong>the</strong><br />
south. It is easy to imagine Kingsdale as<br />
a glaciated valley, with terminal moraines<br />
being deposited at Raven Ray, so enclosing<br />
a large lake. But <strong>the</strong>re is now a way through<br />
for Kingsdale Beck.<br />
If you innocently follow <strong>the</strong> beck by<br />
taking <strong>the</strong> path over Ravenray Bridge you<br />
may be surprised to find yourself struggling<br />
against <strong>the</strong> flow <strong>of</strong> walkers in <strong>the</strong> opposite<br />
direction. Clearly <strong>the</strong>re is something<br />
special downstream – and we soon hear<br />
and see it, that is, Thornton Force, which<br />
many regard as <strong>the</strong> most picturesque<br />
waterfall in <strong>the</strong> Dales. At 14m it is not <strong>the</strong><br />
highest but <strong>the</strong> graceful cascade within a<br />
shrub-topped cliff face seems perfectly<br />
designed for tourists’ snapshots from <strong>the</strong><br />
footpath. It is even possible, with care, to<br />
scramble behind <strong>the</strong> waterfall to enhance<br />
<strong>the</strong> magic.<br />
A better reason for doing so is to<br />
investigate at close quarters <strong>the</strong> geological<br />
unconformity in <strong>the</strong> cliff face. An<br />
unconformity does not just mean that <strong>the</strong>re<br />
is a change in <strong>the</strong> type <strong>of</strong> rock, which is<br />
obvious to even <strong>the</strong> untrained eye, but that<br />
two rocks are adjacent when <strong>the</strong>y shouldn’t<br />
be: a younger rock rests upon an older rock<br />
with an expected intervening middle-aged<br />
rock missing, because <strong>the</strong> sediment ei<strong>the</strong>r<br />
was never laid or has been eroded away.<br />
Here, <strong>the</strong> sediments <strong>of</strong> 350 million year old<br />
Carboniferous limestone lie above distorted<br />
Silurian slates some 100 million years<br />
older, with <strong>the</strong> Devonian layer missing,<br />
<strong>the</strong> whole forming a textbook illustration<br />
Left: Ingleborough from Tow Scar.<br />
Right: Thornton Force.<br />
Kingsdale Beck 137<br />
<strong>of</strong> severe earth movement and erosion. Between <strong>the</strong>m is<br />
a narrow band <strong>of</strong> s<strong>of</strong>ter conglomerate limestone that has<br />
eroded to give <strong>the</strong> overhanging waterfall lip.<br />
<strong>The</strong> region clearly has a complex geology. Chapel<br />
Beck and Kingsdale Beck are crossed by <strong>the</strong> North<br />
Craven Fault, one <strong>of</strong> several Craven Faults that run<br />
across <strong>the</strong> sou<strong>the</strong>rn Yorkshire Dales, from Grassington<br />
This is Chapter 8 <strong>of</strong> <strong>The</strong> <strong>Land</strong> <strong>of</strong> <strong>the</strong> <strong>Lune</strong> (2nd edition), http://www.drakkar.co.uk/land<strong>of</strong><strong>the</strong>lune.html, Copyright © 2010 John Self