The Old Marble Quarries at Cill Chriosd

5th August 2015

 Thin alternating layers of sandstone and limestone?

 Ben na Caillich (Mountain of the Old Lady - I was told there is a Scandinavian princess buried on the peak) north west of Loch Cill Chriosd. This granite mountain is amongst the earliest igneous intrusions on Skye. Somewhere on the left can be found rocks formed by explosive volcanic activity, i.e., a volcanic vent.

On the south west side of the Broadford to Elgol road a dolerite intrusion is exposed. Dolerite is a volcanic rock, similar to basalt but containing crystals visible with a hand lens as it has cooled underground (at a relatively shallow depth) and therefore slightly more slowly than basalt. Granite cools at a greater depth and therefore contains larger crystals than dolerite.

 The dolerite dyke retreating south eastwards from the road. According to Jo this intrudes through Durness limestone {dolostones [mostly dolomite - CaMg(CO3)2] ?} and, for a short distance, through granite. According to some sources the acidity of the granite bedrock around here encourages the growth of heather, whereas a rich growth of grass is associated with dolostones. The name of this area, Strath Suardal, means the dale of green pasture. The picture we saw wasn't that clear, dolerite being more basic than granite but more acidic than dolostones, and the location of vegetation not was not so well defined.

Pink granite.

Looking west down the valley where one can see the existing marble quarrying operation in the distance at Torrin and further still is Bla Bheinn (Blue Mountain) of the Black Cuillin.

We didn't know whether this effect was due to sedimentation or weathering.

This does appear to be weathering.

We thought this might be a fossilized dinosaur foot!

Approaching the remains of a cottage. 

Halfway up the wall lives a tree.

Sedimentary layers of limestone laid down around 480 million years ago when Scotland lay south of the equator on the southern margin of the "North American" continent Laurentia? 

Are these skarns, comprised mainly of magnetite (an iron oxide), formed where granite intrudes calcium-rich carbonate rock and releases hot aqueous solutions rich in silica, aluminium, iron, and magnesium which subject the rock to metasomatism (chemical alteration of rocks by hydrothermal and other fluids)?

A little piece of marble.

Is this granite bedrock or Durness limestone?

Nodules of iron-containing minerals?

The possible site of a seam of marble, mined out many years ago.

One of the many revealing fragments lying around.

Lots of tiny crystals of mineral embedded in this rock.

The remains of an old winch?

Possible signs of the green fibrous mineral serpentine which, according to Wikipedia, is a "group of common of rock-forming hydrous magnesium iron phyllosilicate minerals. This could be antigorite [(Mg,Fe)3Si2O5(OH)4] or the fibrous forms, chrysotile [(Mg3Si2O5(OH)4)] which is a type of asbestos.

What are these wavy lines?

And there were lots of whorly structures.

More serpentine?

A disused marble quarry.

The remains of a building which must have been part of the system for shipping out marble, perhaps a loading and sorting yard at the head of the railway?

And next to this, what looks like a platform at a railway station.

The Creation of Glen Brittle

4th March 2014

Sgurr na Bairnich and Sgurr an Fheadain tower over the head of Glen Brittle (Gleann Bhreatail). This is part of the Black Cuillin and represents part of the northern section of the roots of a massive volcano which erupted on the Isle of Skye during the Palaeogene period, 23-65 million years ago. The original volcano was hugely bigger but has mostly disappeared through millions of years of erosion.

 Glen Brittle runs westward to meet Loch Brittle.

 Glen Brittle is a glacial valley, scoured out over the course of cold periods during the last Ice Age which began around 750,000 years ago. The last cold period occurred 11,500-116,000 years B.C.

 Masters of t'Yooniverse.

 And it came to pass that by Friday evening the job was finished and they decided to have a party. Jesus had been busy making the beer, hinting at a future preoccupation with free alcohol that culminated in his famous party trick during the wedding feast at Cana.

 On the path to Coire Lagan, in the looming presence of Sgurr Sgumain.

Sgurr MhicCoinnich in the middle, just to the left of the Great Stone Shute, and Sgurr Thearlaich on the right. Well, maybe, I'm not sure, but this is part of the western ramparts of the ancient super-volcano.

Great masses of rock (much of the Black Cuillin comprises gabbro) scoured by a glacier as it flowed west towards the sea.

We were looking for a whale-shaped natural edifice etched with striations by small pieces of rock in the glacier and thought this was it, but in retrospect I'm not sure it was.

These looked more like cracks caused by cooling and warming, involving frost, than glacial "scratchings".

The parallel lines just left of centre seem more promising, but if you look carefully you can see some very worn grooves running left-to-right which I think are even more likely candidates.

The grooves are even more obvious here.

The birth of Halley's Comet