Carboniferous Limestone
This is a well-cemented rock of low porosity, and occurring in
thick beds. As they have prominent vertical joints, they can be
easily spilt into blocks for use as building stone. It crops out,
for example, in the Peak District, Mendips and Yorkshire Dales. It
contains most of the country’s potholes and natural cave
systems. Mostly, Carboniferous limestone is either a fine calcite
mud, precipitated from warm shallow seas, or a shelly limestone,
formed by fragments of animals such as corals. It is a very tough
rock, and is commonly used as roadstone, but can also be used for
cement making because it is often quite pure, and as a source of
calcium carbonate for the chemical industry.
Formation of Trow Gill
Trow Gill was formed at the end of the last Ice Age in
periglacial times there were vast meltwater streams. These streams
didn't sink underground through the limestone rock because most of
the rock was still frozen and behaved as if it was impermeable.
This meant the meltwater streams cut valleys into the rock and
then, when the rock thawed out, the river disappeared underground
through lines of weakness in the limestone leaving a dry valley
behind.
The formation of this ravine has left behind a stunning land
scape that has to be seen to be believed .If you carry on the walk
through Trow Gill for another 45 mins you will come across another
natural wonder in Gaping Gill pothole.
To log the cache please upload a photo of you or your GPSr with
the narrowest part of Trow Gill in the background also E-Mail me
the answers to the following questions
1) Estimate the width of Trow Gill at its narrowest
2) Estimate the height of Trow Gill
Any logs without a photo may be deleted