How the Flashes were
formed
The Flashes (or lakes) are a legacy of the town's
industrial past and were formed as a result of mining subsidence.
Some of the flashes were partially filled with colliery waste and
ash from the nearby Westwood Power Station. Ince Moss Colliery
closed in 1962 and Westwood Power Station was demolished as
recently as 1989. Natural colonisation and large-scale reclamation
works have helped heal the industrial scars, turning the area into
the amenity it is today.
A "Flash" shows how a change at one level in
geology can result in multiple changes in other levels. A working
mine is cut, and coal is extracted. The mine is strengthened using
wooden structures, to support the roof. Once the mine has reached
the end of its working life, it is closed off at the entrance.
However, the internal structure remains, and over time, the wooden
support struts will age and eventually collapse. This results in
the creation of a "sump", or a shallow recess, at ground
level. Depending on the permeability of the ground above,
this shallow may eventually fill with water, and create a lake,
known as a FLASH.
About "Coal
Meaures"
There are some technical terms here, so I've provided a link to
each one.
The Coal
Measures is
a
lithostratigraphical term
for the coal-bearing part of the
Upper
Carboniferous System.
It represents the remains of fluvio-deltaic sediment, and consists
mainly of clastic rocks
(
claystones,
shales,
siltstones,
sandstones,
conglomerates) interstratified with the beds
of
coal. In most places,
the Coal
Measures are
underlain by coarser clastic sequences known as Millstone Grit, of
Namurian age. The top of
the Coal
Measures may
be marked by
an
unconformity, the overlying rocks
being
Permian or
later in age. In some parts
of
Britain, however,
the Coal
Measures grade
up into mainly coal-barren red-beds of late Westphalian and
possibly Stephanian age.
To log this
cache
* Take a photograph of you and/or
your GPS at the posted co-ordinates. Post the
photo(s) to your log.
* At the co-ordinates, please
identify, photograph and name one of the
Clastic Rocks described above.
* Explain what non-permeable base
material you see.