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16 October 2014

mountainman - may 2007


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A walk to the Lighthouse and beyond

Friday night, needed some fresh air after a day in front of the PC. Might as well make the most of this good spell since the forecast is for change this weekend. The path from the Calmac pier to the Rubha nan Gall lighthouse is a popular walk although a bit muddy in places. There is also some interesting geology further north so that was tonights objective.

It's not far to the lighthouse - 20 minutes at a brisk pace. the view over to Ardnamurchan is very nice. Pic below (note this was taken on the way back after the sun had set.)



There is a good path to the lighthouse but beyond that, its a bit rough going.A short distance beyond the lighthouse there is an outcrop of rock of Jurassic age. Most of Mull is Tertiary volcanic (ca 60million years ago) but occasionally the underlying rocks which are much older peep through. That's what we have here. Limestones and sandstone, very hard and very sharp - the sedimentary layers are very obvious:


.
Further on and looking back at the cliff:



The sun was beginning to set so but was just right for showing the cliff. Most of the rock in these cliffs is very crumbly basalt with dykes and sills running through it. If this stuff was solid, secure and reliable, then Mull would be a climbers paradise!

Moving on, I knew that there were basalt columns to be found near here. Not nearly as impressive as the Ulva ones, but you can see the form in the pic below.


The rocks are almost completely covered in lichen. From this point onwards, the going is quite rough and eventually you reach a point where the cliff goes straight into the sea. Time to head back! Besides, the light was going.

Time for a couple more pics. Primroses:


And finally, I managed to catch the sun going down behind Ardmore Point:


That's the Hebridean Princess at anchor there. Beautiful night for a luxury cruise!

There are actually some really nice dykes and sills near Ardmore Point- one in particular doesnt even look natural - it's like a man made wall - really impressive! Next time I take a trip there, I'll post it to this blog. That was actually the first field trip I did with the geology class - easy to get to and well worth a look.

That's all for today!
JW


Posted on mountainman at 23:39



Iona for work then Carsaig for play...

It was up early on Wed for the trip to Iona - work not pleasure. Anyway, on the way back, I thougt that Carsaig would make a good detour. I did a geology talk in the sle of Mull Hotel last night, and having spoken about Carsaig a couple of times, I felt the urge to go back!

Anyway,. heres Fionnphort, early in the morning, first ferry about to go:


However, it was after 5pm before I got to Carsaig. Weather wasnt quite so good, but still dry. And midgy.

Carsaig is a geologist's dream. There is stuff of interest absolutely everywhere. For those who have never been there, make it a priority for your next Mull trip. The scenery is spectacular. And the road has been improved as well!

I didnt have a lot of time, but parked the car near the old pier and headed east along the track towards Lochbuie. There are lots of good things to see. The pics below will give you an idea.


A sill cuts across the shales of the rocky shore. This whole area is criss crossed with dykes and sills.

In the same area, the casts of several ammonites are to be found:




That first one is a real beauty. The compass gives an idea of the scale - it is about 4" long. Note that this is just the cast - I wonder what happened to the ammonite itself - whose collection is it in?

Some of the flowers that are common here (thrift):


And some of the inhabitants:


Further on along the shore - the path is a bit boggy in places, so take care, there is a good view onto the shore and more dykes:


Two thin dykes on the shore can be seen , one cutting the other:


Here we see the side of an exposed dyke - the pattern of the joints as they are known, looks like squares. This is the same sort of thing that you get with basalt columns, except these are smaller. These patterns are quite common where dykes are exposed.


And finally, before heading back to the car, a pic of some fossil shells in the shales on the shore (try saying that quickly...)


The Carsaig are is very rich in fossils - many can be found simply lying loose on the shore.

That's all for this quick trip but I'll be back soon hopefully for a look at the other side, west from the old pier. A whole day I reckon. There's some good stuff there....

MM

PS: Many thanks to all who came along to the "Geology and Landscape" talk I did last night, The turnout was very encouraging. From what I gather, there has a been a good attendance at all the Wild Isles talks and lectures this year. Maybe see you again soon!
Posted on mountainman at 21:27



Back to Iona: more work and more play...

Well it was back to Iona again to try to finish off last week's work.Much fun with dodgy routers, dodgy broadband, even dodgier VPNs and a PC with tamper proof tape which wouldnt switch on. Dodginess of the highest order. Of course, the problem was a disconnected internal power lead which lay behind the tamper proof tape..... however, old age and treachery will defeat anything that youth can offer, and service was quickly resumed. The great thing about walking and exploring is that it puts this sort of nonsense into perspective. Now if it would only pay the bills....

Anyway, the stuff you really want to know:
Here is the view, just off the 5pm ferry, looking back to Mull:



Right, Sunday evening after a very nice meal at the best B and B in Iona, and off I trundled to search out what one heretic once described as "jist look like a load o auld stanes tae me". The west side of Iona is beautiful. Even more so in perfect sunny weather and a light breeze. From the machair, looking south ish:



The machair on the left is the golf course, of course.

There are so many nice little inlets with great beaches and tremendous rocks. This one is a cracker:





Most of the rock on the western side of Iona is Lewisian Gneiss, but in several places it is cut by various igneus intrusions of a much later date. These are in the form of dykes and sills. Dykes are approximately vertical and cut across strata - sills are intruded into the existing rocks and tend to be horizontal-ish. Not very scientific I know but you get the drift.



The vertical cleft is a worn away dyke, the red rock at the base of the rocks is a sill of what is referred to in many older books as "porphyrite". Micro-granite is the more modern name for it. It is quite common in several places in Iona and the bright red colour is very distinctive:



Just before heading back again, here is a view from the shore looking up at one of the very distinctive craggy knolls that are such a feature of the Lewisian gneiss:



I think that is Dun Cul Bhuirg in the picture. The blackish looking rock on the shore is an amphibolite - quite common on the west side.

The sun going down looked impressive:



And so, back to the B&B and off to bed...


Next morning, up nice and early, there was a beautiful thin crescent moon hanging above Fionnphort, but the pic did not turn out well - looked really nice as well. Never mind, the sky did look fine and moody later:



I headed down towards Traigh nan Siolag and the cliffs above the shore there. The rocks around here are Torridonian, not so old as the gneiss on the west side, but still as fascinating. Every so often, there are "erratic" boulders of Ross of Mull granite to be found, brought westwards during the ice age, carried by glaciers. Here is one on the cliff top:



And here is another, down on the shore:



The whole area is covered in granite boulders. The Ross of Mull granite which of course is the beautiful pink rock that you find at Fionnphort actually outcrops on the little islands just off the east coast of Iona. So the contact between the granite and the Iona rocks must lie just offshore. The little Island in this pic is made of granite:



Eilean Carrach, I think that one is. Well that was it for the morning walk - back for breakfast and then to work.

Later in the afternoon, I met up with Angus Miller who runs Geowalks. Angus specialises in geological tours all over Scotland (he is based in Edinburgh) and he has regular trips to Mull and Iona. Check out his web site - just do a search for geowalks - it is well worth looking at.

Bye for now

James





Posted on mountainman at 22:10



Gribun shore with Junior

18th May: Friday morning and it was a case of "Where shall we go?" The weather wasn't great but we needed a trip somewhere - the coast along Loch na Keal and Gribun can be quite interesting in bad weather - and the rocks are neat as well, so off we went. Actually, the weather was not too bad - windy rather than wet - white caps on the waves were plentiful. On the way towards Gribun, on the shore of Loch na Keal, I notice that the sun was really picking out some rocks on the opposite shore:



This pic is an enlargement of an image taken at the full telephoto setting of the camera - so it isnt great, but shows the columns well. Whether this is a sill or a lava flow needs more study. Quick update on Saturday: Having checked the maps and the Survey memoir, it appears that it is just a lava flow like so many others and not a sill. It looks similar to the columns in Ulva and may well be related.Need to get down to it some time and have a look!

On to Gribun - not a lot of good places there to park a car but just opposite Inch Kenneth there are a couple of places. We walked along the shore to a headland that sticks out towards Inch Kenneth.



The rocks in the foreground are a very hard limestone type of rock called cornstone - there is a lot of it in this area - there is also a lot of sandstone and conglomerate, all of Triassic age so this is a good place to see sedimentary rocks. There is a very distinct green sandstone found here. the next pic shows the junior geologist examining it closely (No he wasnt asked to stand there just to give a sense of scale...)



I noticed a very freshly brokern surface in this sandstone nearby. Probably some geologist hitting the rocks! One of the very distinctive things about this rock is the dessication cracks that cover it. See this pic:



and this one:



The cracks were caused by the rock drying out and then being infilled by soem other material. Judging by the colour, I would say that the infilling material was iron rich - it is certainly very different from the sandstone. It is also more resistant to weathering, so it stands up, proud of the surface.

The weather started to change and so it was back to the car with Iain.

Further back up the road, near Scarisdale Point, I stopped to have a look at something that relates to much more recent geological history. There are some very obvious grooves and channels cut in the shore rocks here. These are known as P forms, and represent the gouging effect of glaciers on the rock. Go to:

http://www.swisseduc.ch/glaciers/glossary/p-forms-en.html for a good explanation (and a picture from elsewhere in the Highlands)

Here are the Loch na Keal P Forms:





The whole are is cut by dykes as well, some of which are very interesting, but that can keep for another blog entry!

Actually, this whole coast is full of interesting stuff, it is also easily accesible and with the soaring cliffs behind you and great seascapes in front, you just cant go wrong!
Posted on mountainman at 13:04



Glengorm and great views

Had a quick visit up to Glengorm today -there really is a great network of paths and tracks there and it is really nice and safe place to take the young ones. And the views on a clear day are excellent. We headed down to the shore, straight down from where the cafe is really, beautiful weather and just great for walking about in that carefree sort of way.

Couldnt keep away from the rocks however - the whole of North Mull is basalt, criss crossed with dykes and sills - some of the best places to see these are on the shore from Ardmore round to Glengorm. Lots to see. Some pictures below which should give a flavour of the place.


The view over to Ardnamurchan - great weather!


A sill cutting across the rocks on the shore - really obvious it was. I know there is not much to indicate scale, (didnt have my hammer with me, as on other trips) but it was no more than 4" in thickness. Here's a closeup view of it:



And if you look at the top surface, which is visible in a few places, you can see the jointing really well - these rough polygonal shapes are similar to how basalt columns form.



This type of thing is quite common in the area. Another very good example can be seen near the Ardmore Point light - this was where my geology class had their first field trip. Again, a good place for a quick trip and lots to see.

We also came across a dyke cutting the basalts, but it wasnt too photogenic. I noticed that there were several round holes in it. It had obviously been sampled by geologists in the past - they use a special drill to cut out small cores from the rock. In many cases this is much better than whole scale hammering, but it does leave unsightly holes. Ideally, the holes should have been filled afterwards.

A boat came into view, lifting creels:



And the view further round the coast to the west looks like this:

The great thing about this sort of place is that you can spend hours just wandering about looking at stuff. A word of caution however - some of the basalt rock is very crumbly - not nice to climb on. Treat it with respect!

And then it was back up the track and off to the cafe for refreshment. Coming back into Tobermory, you pass by this little hillock at the side of the road:



This is Creag a Chrochair - its a volcanic plug. Same sort of thing as 'S Airde Beinn not far away. There is also a thin sill cutting across it - you can see it in this enlargement of part of the pic ( the horizontal band on the right hand side)



So that's all for now - just a quick trip I know, but its amazing what you can find if you know what to look for.

All the best! MM.




Posted on mountainman at 20:39



Iona, yet again..

Well, it was back to Iona again, via Bunessan and Kintra fro a couple of jobs that needed doing. Weather didnt look too promising this time, so I wasnt too hopeful of getting in much "rock time".

After getting the work done on "mainland" Mull, it was the 17:45 ferry to Iona and check into the B and B.

Joyce and Lindsey suggested going to the old marble quarry, so accompanied by Nipper the dog, off we went!

Heres the view northwards from the track over to the marble quarry. As you can see it is a bit damp looking. Damp underfoot as well!




Then onto the quarry. Nipper found it all very interesting:



Nice block of marble you've got there Nipper! Would make a good kitchen surface if it were sliced and polished.

Heres the view to the south east:



No matter what the weather is like, the sea always seems to be rough at the quarry. How on earth they managed to get boats in to get the marble out is beyond me. There is virtually no shelter. Must have been quite hazardous.

Heres another view of the quarry showing lots of blocks of marble:



The dark looking rock immediately behind the marble blocks is known as the "Green Rock". It is a sort of amphibolite - a metamorphosed igneous rock. Quite different from the marble.

On the right hand side, about half way up the pic there is another light coloured rock. This is the stuff called anorthosite. Anorthosite is interesting. It is quite rare, it is found on the moon. And it is the stuff that the super-quarry in Harris would have exploited. In Iona, it occurs near the marble quarry, but is quite different from the marble - much harder, and more of a creamy white in colour.

After a well earned cup of coffee, we were ready to head back:



But before the soggy trudge back, here's a quick pic of some of the swirly, contorted folding that you can find in metamorphic rocks:



Check back soon!
Mountainman


Posted on mountainman at 21:56



Ulva Ferry - columnar stuff ...

Last week I remarked on how the sun was shining on some rocks on the north side of Loch na Keal. Today I decided to investigate it. After a few IT jobs in Salen, the idea of luinch near Ulva Ferry seemed a very pleasant one, so off I went.

After driving out westwards for a few miles, I came to a place where the rock has been getting quarried, a good place to park the car. Actually, ther is a lot of geology to see here, so maybe get back to you on this sometime.

I headed on down through trees, bog, rock, bog, tussocks, bog, water, wet stuff,, bog, stinky, mushy yeuchy stuff, oh yes and more bog, until I reached the shore.

Ahhhh. Blisssss. hard rock! solid rock. Something you can stand on. Without a schloooooooping sound.

The view westwards was great -look at those basalt columns:


This was the stuff that I saw from near Gribun last week.

Further investigation showed some very interesting features - a sill which splits in two:


Notice this bifurcating sill - it splits in two - the upper prtion being much thinner than the lower part.

At this point the baslat clearly shows its polygonal columnar structure:


The polygonal structure is clearly seen in this pic.

Moving on a bit:


The view over to Ben More is great! It looks really "pointy" from this angle. Wonderful view!

Moving on a bit, we can see the view to Ulva Ferry itself:



And then back up on to the cliffs fro a view back to Ben More:



Nice view over Loch na Keal. From here it was a simple walk back up to the main road and back to the car. Hope you enjoyed this short trip.

All the best, Slainte!

Mountainman

Posted on mountainman at 22:30





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