Re: Very few trees in Scotland

PJ Halls wrote: 
« Paul » wrote:

Thanks everyone.
I have been reading about Hadrian's Wall and have a book on it that I got from the
English Heritage.  There are lots of panoramic views in the book.  Every view is
lacking trees.  The wall is run on the top of grass covered outcrops from coast to
coast (more or less).  I have a small chunk of black rock from an outcrop from
near Housesteads.  It is the same stuff the wall and fort at that place is made
of.  I brought it home thinking it was SS or perhaps basalt.  However,
concentrated HCl reduced a small piece of it to nothing in just a few minutes.
Fairly soft also.
Paul.



This is exactly the same issue as in Scotland: sheep (or, as a forrester
friend prefers to call them, 'land maggots').  Hill sheep, especially,
will eat almost anything green and chomp it close to the ground.  The
net effect is close cropped turf and no trees, except where the sheep
cannot get.

Your 'black rock' could easily be Carboniferous limestone - parts of the
Great Scar Limestone are pretty black to look at, or could be magnesium
limestone, dolomite.  The difference to the basalt/ dolerite of the Whin
Sill is hardness and grain size - as well as whether it dissolves in
HCl.

Peter



First of all, for those that haven't realised, Hadrians Wall is not the border with Scotland and as far as I am aware never has been. It follows a natural defensive line from Wallsend (near Newcastle upon Tyne) to the east, to the Solway firth northwest of Carlisle. for much of its length it follows an outcrop of the Whin Sill, a white speckled dark grey quartz Dolerite (QD). The Whin Sill can be found at several other scenic locations from High Cup Nick near Dufton on the western side of the Pennines, Cauldron Snout, Cronkley Scar, High Force, Low Force and the quarries near Middleton in Teesdale, Stanhope in Weardale, and several locations along the Northumberland coastline.

In some locations (such as Teesdale) there is a range of grain sizes within the Whin Sill from glassy or very fine grained materials at the margins through to pegmatites with magnetite crystals up to 10mm long.

There are several locations where the Carboniferous Limestone and Whin Sill can be confused if for example there are no obvious fossils in the limestone. Adding dilute Hydrochloric acid may result in little reaction from the muddy limestone with a stronger reaction from the dolerite, except the dolerite gives a slight smell of hydrogen sulphide (rotten egg smell).

Not certain but I don't know of any locations where dolomitic limestones (Permian deposits in this part of the world) are present near wall. In any case the dol lst around here is typically a light yellow brown colour and often recovered as a silt where altered or weathered.
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