Mull Geology

This mornings walk was to the old quarry at Bloody Bay, north of Tobermory. The rock from the quarry was used to build the approach to the Rubha nan Gall lighthouse a little further south. The rock is a nice red sandstone, slightly enigmatic. According to the BGS Map, North Mull and Ardnamurchan, 2013, the stratigraphic position of this rock isn't certain. The map carries this legend: So it is possibly Jurassic. There is a description in the Ardnamurchan and NW Mull Memoir: "Prof Judd drew attention to a red sandstone quarried in the west cliff of Bloody Bay... The locality is about a quarter of a mile SE of Ardmore Farm and of easy access from above.....the eroded surface of the the sandstone is seen to be directly covered by the basaltic lavas.. The sandstone is of good quality and has been used in the wall of the path leading to Rubha nan Gall lighthouse. It is at least 50 ft thick, current bedded and red in colour with a small proportion of rounded grains. It...

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...

'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" ...

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 -...