大象传媒

This is just a quick note to say thanks to all the students who took part in the recent geology night class at Argyll College. I hope you all got as much out of it as I did - it was great fun! Hopefully you all learned something as well.

Anyway, next trip is the Iona one on Saturday 14th. Here's hoping for good weather. According to the 大象传媒 forecast, it shouldnt be too bad.

Actually, when it comes to forecasts, one of the best is Geoff Monk's Mountain Weather. www.mwis.org.uk It is aimed at walkers, climbers and skiers really, but it tends to be quite accurate and gives a good general forecast as well. Have a look.

Next geology trip will be to Scoor / Uisken / Ardalanish on the 28th. Exact itinerary is to be worked out yet.

So that's it. Thanks again and I'll see you soon.

In the meantime here are a few Ardtun pics:

On Saturday, the 14th we had the Geology class field trip to Iona. This had been postponed in the past because of adverse weather, but this time the weather more than made up for it. Not particularly sunny, but warm and dry with a gentle wind. The light wasnt great for taking photos (see notes below) as it was very hazy, but apart from that, the weather was superb.

It was a very good day for observing all sorts of things, not just the rocks!

Hopefully you all enjoyed it - it was certainly a great day out - we didn't get to see as much as I had planned, but I am sure the other stuff can keep for another trip.

Actually, Iona is well worth visiting when the weather is wild - you see a completely different aspect of the island.

Remember the next field trip is to Scoor / Uisken /Ardalanish on the 28th. Dinner at Mediterranea will be in the evening, probably at 6pm. I will be emailing you all before then of course!


Stay tuned and thanks for being such a great class!

James

Here are some Iona geology pics (note these were taken about a fortnight ago, when I was planning out the trip, not on the day of the trip as the lighting wasnt very good)


Glacial erratic boulder of Ross of Mull granite sitting on top of Torridonian rocks of Iona



Lewisian Gneiss in Iona, with epidote veining (the green stuff)


Pebbles on the beach at Port na Curraich - St Columba's Bay



Port an Fhir-bhreige, west of Columba's Bay



Heart shaped xenolith in granite boulder at Port Ghoirtein Iar. Many of the granite boulders found on the south east of Iona have these xenoliths in them.



The Marble Quarry in Iona - looking inland from near the sea. Note the large blocks of quarried marble.

Had been meaning to get over to Ulva for some time, so with good weather and th fact I was working near Ulva Ferry anyway, I had a quick visit to get some pics of the basalt columns that are found on the south coast of the island.

Someone once pointed out that the columns on Ulva are second only to those in Staffa. Not sure if I would go that far, but they are certainly impressive and fairly easy to get to. Well worth a visit.


Basalt Columns in Ulva. Looking south east across Loch na Keal

A columnar basalt stack




A sill running across the shore - contact with the basalt was very clear and the chilled margin really obvious.




A closer in view of the columns




A close up view of the columns - just like steps!




Looking down onto the columns - hexagon shapes very obvious




Looking westwards to the main columns

'S Airde Beinn. Even the name is evocative. Why isnt it "A' Bheinn as Airde" if the name really means the "highest mountain"? A fascinating little hill and an absolute classic of the type of hill that isnt all that high, but has tremendous character. Munros? Pah!

Anyway, I was sort of near it, and round it, but not quite "up on it" today - maybe later this week when the weather is better. Its not a big deal anyway, 40 minutes to go up and down including all the way round the top of it.

So what makes it special?

First let's look at a popular misconception: SAB is a volcanic plug. It is NOT a volcano per se - it is an example of a feeder system for the lava flows that cover north Mull. It is well described in the Mull Geological Memoir. So why does it have a crater? Well, it would be nice to think of it erupting and building up like some sort of Mull version of Fujiyama, but the reason is a bit more prosaic than that.

The "crater" is actually a glacial depression, filled with water (Lochan S Airde Beinn). A geological fault runs all the way through it, and this has probably provided the line of weakness which was gouged out by the glaciers, and is now filled with water.

The rock itself is a very coarse dolerite, the same sort of material that makes up the rocks that Edinburgh and Stirling Castles stand on. SAB is actually a very important geological site - it gets listed in the governments Geological Conservation Review papers and web site. If you want to know more, a lot more, try this:

http://www.thegcr.org.uk/Sites/GCR0021.htm

Numerous other Mull sites are listed in the GCR, such is the importance of the island to igneous petrology.

So the next time you are up there, just stop and think, you are on top of something quite special - but I think you knew that anyway! Pics below:

Now how about a real close up view of this place? These wide angle shots are all very well, but what really lies beneath your feet?. REAL close up as in 30 microns thick, under a geological microscope, in plane polarised light:

And the same stuff again, this time in crossed polars, looks quite coloirful doesnt it? Amazing how a dull looking piece of rock can appear when ground thin and seen through the microscope:

Many, many thanks to Rob of Geosec Slides in Spilsby, Lincs, who visits regularly and makes thin sections of rocks like these. Some rocks are truly amazing under the microscope. Rob has an Ebay shop where he sells these slides: http://stores.ebay.co.uk/Geosec-Slides, These 2 pictures of the rock in thin section are HIS, not mine, by the way!

Mountainman

Well, that's it then - the final trip of the current series of classes. We had a great day on Saturday 28th in the Ross of Mull. The turnout was excellent - it is always encouraging when you finish a course with more students than you started with!!! Anyway, first stop was Ardalanish Bay to look at the rocks there - the whole area just buzzes with geological interest -everywhere you look there is something.

I have put up some pics below to give you a feel for it:


Ardalanish Bay - nice folding in the Moine schists in this pic

After Ardalanish we had a quick little trip to Uisken for lunch and then headed off again, up to Scoor.


This rock seen in the pic above is a garnet amphibolite, near Uisken. Notice the size of the garnets (the ruler is one foot long) . This rock outcrops in several places between Ardalanish and Traigh Bhan na Sgurra, the beautiful bay below Scoor. The garnets although very large, are no good as gem stones as they are full of inclusions and quite impure. However, to find garnets of this size is unusual. Actually, some of the best examples are found as beach boulders - when eroded and polished by wave action, the garnets are really obvious in the rock. I'll try to find a pic for you!


Incidentally, my very first trip to Mull was as a geology undergraduate from St Andrews and we stayed at Scoor House - Nov 1979 it was.

There is a great little car parking area near the Kilvickeon church - anyone know how old that is? - from there it isnt far to the beach. And a great spot that is - beautiful, sunny, clean sand and no-one else about! We had a lot of fun investigating a sill intruded into the Moine metamorphic rocks - made more entertaining by the incoming tide so there was a bit of rock-hopping needed!


The beach at Kilvickeon - the island is connected by a sand bar - a feature called a tombolo. Most of the rocks in this pic are Moine schists and psammites (AKA quartzite) However, a sill has been intruded into the rocks on the left hand side of this pic - it isnt too obvious in the photo, but when down on the beach, the sill shows up as a very distinct brown rock in the grey schists.

The sill sof the Ross of Mull are famous for their xenoliths - xenoliths are large lumps of the surrounding "country" rock that get caught up in igneous intrusions. There is an absolute beauty at Kilvickeon:

Xenolith in the sill. Shaped a bit like the Isle of Wight! You can get a sense of the scale from the hammer (you can just see it - it has a blue handle and is about 12" long)

Here's another picture of the beach:

Looking westwards across Kilvickeon Beach

Final stop was the cliff above Port Bheathain - unfortunately we didnt have time to check it out properly as we had to be back in Salen at 6pm for the celebratory end of course dinner. The highest point here is a "dun" - Dun na Ceaird. A very fine vantage point witha great view of the beach below:

The beach below Dun na Ceaird, looking towards Port Bheathain. The coastline here is characterised by long promontaries and inlets with white sandy beaches.

Final picture is from the shore looking back towarsd the cliffs - note the almost vertical schists that are found here. The rocks are very shiny in places because of the large amounts of mica in them. When the sunlight catches them it can be quite impressive!

After this there was a bit of a sprint to Salen for dinner at Mediterranea!

Finally, just to say, this has been a very enjoyable experience - you were a great bunch of people to work with and I hope you all got as much out of it as I did. This is not the end of the story however - there will be more geological events over the summer - I shall keep you posted!

Thanks to everyone for taking part and I hope to see you all very soon!

JW (mountainman)