CHAPTER 8: The Greta Headwaters

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