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16 October 2014

mountainman - August 2007


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This is just for information, rather than to show you any pretty pictures! I am hoping to get the geology classes and field trips up and running again sometime soon. Hopefully I can do this through Argyll College again.

Last years were very successful and I would hope to be able to repeat that this year again. I'll keep you posted via this site as well as my own www.mullgeology.com

Also, the Scottish Geology Festival is back again, in September and there will be numerous events happening all over the country. If you want details, see www.scottishgeology.com

There was supposed to be a "social event" to celebrate the end of last years classes, but this didn't happen for a variety of reasons. We are hoping to have this fairly soon, so keep watching.

Another event which is being refined at present is for some of us to walk the length of the famous Loch Ba Ring Dyke. This dyke is a classic of geology, worldwide, not just as far as Mull is concerned.

This trip will be quite strenuous and obviously weather dependent, so here's hoping for good weather.

On a different tack and a different "ology" (No actually, its an "onomy" MOST DEFINITELY NOT AN OLOGY!!!) there is a major astronomical event happening soon. The Perseid meteor shower, which reaches its climax on the 12th of August, takes place this year against a sky with no moonlight as the moon will be in its New phase. ie conditions should be perfect, assuming that the sky is not cloudy.

Look to the north east after midnight and hopefully you will see meteors at a rate of maybe one per minute. The rate increases towards dawn.

Right that's it, the weather is pretty awful right now - been pretty poor for a few days now, so no nice pics of rocks and stuff. I did try, but the best I could get was this one on Sunday afternoon of two junior explorers at Kinloch bridge:



Despite the weather, they really enjoyed. Something to do with puddles, trousers and getting soaked....
Posted on mountainman at 18:48



Near a famous cave

Well it was back to Iona again on Thursday. I usually travel down from Tobermory on the Glen More road, returning by Gribun on the coast road. The Gribun road isnt nearly so fast, but the scenery on a good day is superb.

And more to the point, there are some rather nice places along the way to go and look at rocks and stuff! A lot of the good things to see are actaully right beside the road or not too far from it.

Anyway, near to Gribun is Mackinnons Cave which I hadnt been to for a long time. The tide was actually too far in to go to the cave itself, but the rocks round that whole area are simpy fascinating, Huge soaring cliffs, jagged rocks, pounding seas and birds shreiking. Tremendous stuff.

I parked the car at Balmeanach and followed the well sign posted path. First thing of interest is in the cliffs up above - a "transgressive " sill can be seen cutting across the lavas, meandering like a snake:


Actually, its not too clear at this resolution - you'll have to take my word for it!

Down to the shore and the cliff scenery starts to take shape:



The walking is quite ruggged in places and also muddy in parts. Watch for the tide as well!

Looking back the way, the inclined rocks you can see are quartzites, or psammites to give them the more up to date term. These rocks are very distinctive here - metamorphosed sandstones, with a very regular dip of about 40 degs.

There is rather a fine waterfall near the cave:



The tide was too far in for getting into the cave itself, so that was as far as I went. The entrance to the cave can be seen, sort of in this pic:



A wild place!

Heading back the way,the psammites show very clearly their sedimentary origin. The various layers are very obvious:





The pen is about 5 inches long, just for scale.

A very distinct quartz vein cuts across the psammites:



Although a lot of the rock is psammite, there are huge boulders of the various sedimentary and igneous rocks that outcrop further up the cliffs. One of the great things about this area is that you get the "big three" - igneous, sedimentary and metamorphic rocks all occuring together, and showing tremendous variety as well. The sedimentary rocks are conglomerates, limestones, sandstones and stuff like that. Some of the boulders are huge.



That grey stuff in the foreground is a conglomerate - all from above! Some of it almost looks artificial, like concrete. A close up view shows the pebbles embedded in it:



Looking out to Inch Kenneth, we can see the psammites that make up the foreshore - the rocks have a very distinctive "jointing" pattern - looks like hexagons and triangles:



Close up:



Finally, just before heading back up the cliff path and then back to the car, I found this rather neat orchid:



See, I'm not all hard rock - got a softer side as well!
More rocks soon!
MM


Posted on mountainman at 22:32



Ardmore again, beautiful day

Well it was back out to Glengorm yesterday afternoon - a great walk out there along the main road and then back via the track through Ardmore Forest. What a difference in the weather! And it is supposed to be good all week as well. Hope so - some of us are planning a major walk this Saturday coming, and a week of good weather to dry out the ground would be super.

Anyway, the forest track is a good stroll - been there often enough in the past - but today, it definitely had a bit of an autumnal feel to it. And with the good weather and good light it was a fine day for taking pics!

The view over to Kilchoan was good:


Heres another, a bit further on:


Ardmore Forest is a really neat place to see a lot of the features that are characteristic of the type of igneous rocks in the area - great swathes of what are called Plateau Basalts, the sort of thing that is found in places liek Iceland today. In fact some people reckon that Mull a long time ago would have looked a bit like Iceland does today.

A lot of the rocks are full of white crystals, mainly what are called zeolites. Whole areas of rock can appear spotted:



The pound coin gives an impression of scale (No child present today....!) In close up (these macro lenses are good):


These "amygdales" as they are called are quite small, but occasionally, large crystals can be found. When the Forestry get digging out new quarries for rock, I always get excited (sad, I know, but hey... we're talking rocks here)
Further alomg the track there is a really, seriously bright red "red bole" as its known - I've reported on these on other blog entries but this one is a cracker:



And seen in close-up with a bit of flash:


The red colour really stands out. That's the top of an old lava flow that you are looking at there. Would have been impressive at the time it was being poured out...

Definitely Autumn, its Toadstool Time:



There are several ruined houses in the area - now that a lot of the trees have been cut down, they are really obvious. Here's a couple:



So that was it - a really nice afternoon walk. It was good at nigt as well (steady, mountainman, steady...) No what I mean is the stars were pretty impressive. Definitely Autumn. Jupiter low in the west, seriously bright and the massive red giant Antares, just visible beneath him, grazing the horizon. Antares is one of the biggest stars known - pity it is hard to see from these latitudes. Just for reference, here is a link to give the impression of scale:

The Size of our World, its called:
http://www.rense.com/general72/size.htm

Thought provoking. (I have a feeling I may have referred to this link before, if so , apologies, if not, check it out - it is remarkable)

More mountainman madness soon!

Cheers
James



Posted on mountainman at 10:37



Loch Ba - The Ring Dyke Walk - well part of it anyway

On Saturday, 25th we (my geology students and a few others) planned to walk, at least part of the world famous Loch Ba Ring Dyke. At the time of its discovery, this was called the "most perfect example of a ring dyke known to science" and it represents one of the very last examples of igneous activity in Mull, if not the UK.

So its kinda special. And we had decided that walking the whole length of it was a good idea. Well, yes it is, if the weather is good. Saturday morning was wet. Very wet. The ground was saturated, the streams were seriously full and we all got soaked. But who cares? We had fun. Lots of it.

So for any of you who think I only go out on good days, this was different. Very different...

If you want some info on the Loch Ba Ring Dyke, my own geology pages have a whole section on the walk at: www.mullgeology.com/LBRD_walk.html Also there is a good section on the scottish geology portal site:

http://www.scottishgeology.com/outandabout/classic_sites/locations/mull_loch_ba_ring_dykes.html

Anyway, what did we see?

Th LBRD runs from Loch Ba up on to Beinn a Ghraig down to Glen Clachaig, round Beinn Chaisgidle, over to Glen Forsa and then back over to Loch Ba. It is about 15 miles in length. The most obvious part of it is the section running up to Beinn a' Ghraig, where it appears as a definite feature against the skyline. Ring dykes are also found in Ardnamurchan as well as Glencoe.Although the LBRD is one of the last igneous events in Mull, it is actually traversed by some later dykes. One of these has weathered out to give this chasm:



Here we have a classic example of a dyke that has eroded away to leave a steep sided gorge. The river that runs through it was absolutely charging through! Here is a picture taken a few weeks ago to show it when it was dry:



There is an interesting aspect to all of this. The word "dyke". In Scots English, it means a wall. In English English, it is a ditch. Since a geological dyke (or dike if you are American) can look like either a ditch or a wall, then the word is most apt. Incidentally, the Gaelic word for ditch is "dìg" pronounced jeek (with a long ee sound) which is much more like the English usage than the Scots.....

We walked up a bit onto the dyke itself - the rock is fascinating, being a mixture of basic and acidic igneous material. In this picture you can see swirls of basic material (basalt) in the main rock type which is acidic - called a felsite. This combination of both types is actually a highly unusual type of rock.



However, the weather was pretty grim so we decided that it would be best to head over and down and call it a day. A quick lunch stop took place beside a lochan - look at the mist:



Wet but quite happy (I think)! As always, if there are toadstools to be snapped, I'll take its pic:


That one was about 2" across.

From this point, just south east of the dyke, we needed to head down to the estate road. It got rather interesting at this point. There are several small streams to cross. Normally, these are a doddle. Not today. Because off all the heavy rain, they were seriously swollen and were actually a very good illustration of the dangers that can exist in the hills at any time of year (its supposed to be summer in mid August...) However with a bit of care we got down OK

And then it was back to the cars at the end of the road. Great fun, but the complete Ring Dyke walk will have to wait for a better day! And then there was the social evening later - many thanks to all who attended and a huge thanks to Alison and Vic for letting their house be taken over for several hours. A great evening and hopefully I'll see you all when the classes start again in a few weeks time!

Just to finish with, here are a couple of pics of what it SHOULD look like up on the dyke: (Note these were taken some time ago)


Up high , the dyke just looks like a wall of rock at the back of Beinn a' Ghraig


And this pic is the view back down the dyke towards Loch Ba


Posted on mountainman at 16:48



Pillows...

Every now and again the opportunity arises to get out and about with a professional geologist. I had this occasion today, Thursday, well the morning anyway. Dr John Faithfull works at the Hunterian Museum in Glasgow, but was up on one of his many visits here. We had agreed to meet up and try to locate the "pillow lavas" above Loch Sguaban in Glen More.

What's a pillow lava? Well, to put it simply, if lava gets erupted under water, either in the sea or into a crater lake, it cools quickly and forms distinctive round pillow shapes. These are found in central Mull in various places and have been used to deduce the presence of a large crater lake way back in Tertiary times.

Today's project was to track down these locations

It was wet to begin with but gradually got better - we had a great day. And we found the pillows after much searching. Pics are better than me rabbitting on, so here we go:


This is the start of the walk, at Loch Sguaban. Note the crannog in the loch. Its quite boggy and tussocky here, so we were keen to get as far uphill as possible.


However, there were stepping stones to cross. Fun that was let me tell you....


This is more like it. Rock. Hard Rock. Lots of it. Here we have an intrusion breccia. Good word that. The basalt that lies at a higher level has been intruded and generally chopped up by other igneous material. Very common in this area.


Heres this sort of thing again.That's John's GPS in the middle there for scale. Actually it looks better in a larger pic - these small pic sizes dont do the subject justice.


The view over to Glen Forsa was a bit misty as you can see above


Like most of Mull there are lots of dykes crossing the rocks. This one shows very clearly what is called a chilled margin - where the hot rock comes in contact with cooler rock, it cools much faster and can develop a different appearance and a much finer grain size. Geologists get all excited about this sort of thing.


Here's another example of chilling. Actually, there was a lot of stuff that I saw today that would be great as a teaching resource. Any students of mine reading this, be warned, you'll see these pics again. Bigger. Better.

Time to find those pillow lavas. Not easy let me tell you. We had consulted a recent publication which gave a grid reference. The grid ref was hopelessly wrong...


No this isnt it either - this was an odd looking rock - it appears a bit like the stuff that makes up the Loch Ba Ring Dyke (qv) - one type of rock with bits of the other kind in amongst it - strange, and I dont think its mentioned in the Memoir or other books on the subject. The pillow lavas had to be close:


This is more like it. Lots of rounded lumpy looking bits. Fascinating to think that when that lot went hard, it was molten rock pouring into a crater lake. Now on a wet miserable day above a tussock defended Loch Sguaban, it looks like this. Well we got all excited about it. So there.

Back down the hill again after taking some more pics and measurements, GPS stuff and notes. This isnt just for fun you know, this is to help further the public understanding of science. And my students will be the first victims when the nw classes start up! Hah!


One last view of Loch Sguaban and the crannog from a heathery knoll.

What a great morning that was - the pics at this resolution probably dont do it justice, and the weather and lighting was about as flat as you could get, but we saw what we came to see and a whole lot more..

More mountainman madness soon!
MM
Posted on mountainman at 15:01





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