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Showing posts from March, 2018

Glac Mhor - Columnar basalt

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Afternoon walk today was to Glac Mhor, north of Tobermory. Its a small inlet on Bloody Bay and easily accessible by a rather obscure path through the Ardmore Forest. The great thing about this are is that you can find nice columnar basalt here  - nothing on the scale of Staffa or Ulva, but it is columnar nonetheless . It is mentioned in the Mull Memoir (Bailey et al, 1924)

Here are some photos of the area - as well as the columnar basalt there were a couple of other goodies on the way back!





















General view looking down on Glac Mhor























Two view looking over to Ardnamurchan from the shore





















A view of the columnar basalt at the shore. Some close up pics next:





Columnar structure is well seen.

And another couple of pics of this rock:


Ben Hiant in the distance there

From the shore I walked up the slope back towards the forest. There is an amazing dyke on the way. It is one of the "Mull Swarm" Palaeocene dykes but is seriously feldspar-phyric. SOme massive phenocrysts in there. Here are a …

Evening Walk up 'S Airde Beinn

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'S Airde Beinn is one of my favourite walks in North Mull. It is not far from Tobermory where I live and it gives great view for not a huge amount of effort. Hadnt been up for a while and tonight seemed like a good opportunity now that the clocks have shifted to BST

Contrary to what you might read in a lot of places, SAB is NOT a volcano and the hollow in the middle is NOT a crater. It is a volcanic plug - the hollow is probably due to glacial erosion. SAB is an example of a feeder conduit for higher level lava flows which have since been eroded away. There is another similar plug called Creag a' Chrochair on the road to Glengorm, as well as two less obvious ones on the shores of Loch Frisa. All four lie on the same approximate line

There is an excellent description of it in the GCR report for the site:

GCR S Airde Beinn (click on the link)

Here are some pictures:

 Approaching from the south





















The lochan "Lochan 'S Airde Beinn"


 Beinn Hiant in the distance


 Looking …

North Mull Mesozoic Rocks (3) North of Ardnacross

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On the BGS map North Mull and Ardnamurchan, there are a couple of small outcrops of Mesozoic strata just south of Tobermory and north of Ardnacross Farm. These are the rocks that underlie the volcanics. The volcanics are of Palaeocene age ( approx 60 million years old) but the underlying Mesozoic rocks, depending on exactly what they are can be from about 248 million years ago up to 65 million years. So depending on what they are, they could be considerably older

Rocks of this type probably underlie most of Mull but it is only in certain coastal locations (and also as xenoliths and in volcanic vents) that we can readily see them.

This particular outcrop had intrigued me for a while and it was long overdue a visit. Many thanks to Rory Forrester of Ardnacross Farm for letting me explore at leisure!

The view down the sound of Mull is great:

The Sound of Mull looks quite wide at this point. Ben Talla has snow on top as do the hills above Craignure
Its not just the geology - there is a bro…

North Mull Mesozoic Rocks (2) North of Rubha nan Gall

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This week's Mesozoic outing was to the area just north of the lighthouse at Rubha nan Gall, just north of Tobermory. This is one of the few places in North Mull where the rocks that underlie the Palaeocene volcanics can be seen. It is easy to get to the lighthouse now as the path has been upgraded. From the lighthouse beyond to where these rocks are takes a bit more effort but nothing too hard.And the views are superb.

I had been to the lighthouse last year. Details are here:

http://mullgeology.blogspot.co.uk/2017/11/lighthouse-path-walk-19-nov-2017.html

Hopefully not repeating myself this time. Anyway, here are some pics and information about todays walk:

Pictures and details below:


































Donations box at the start of the path - still more needed for maintenance



Dont know how I missed this the last time I was here a few weeks ago - a dyke cutting through the lavas. You can see the dyke "side on" a little bit further along the path and I think it may be the same dyke that is se…