'S Airde Beinn


S Airde Beinn, Grid Ref: NM 475527 (pron.  SARSJE BINE approx) near the Mishnish Lochs just west of Tobemory is an elongate rocky hill, 295m in height. It is the highest point on the North side of the Mishnish Lochs.


S airde Beinn

The hill is a volcanic plug, composed of a rock called dolerite, the worn down stump of a magmatic conduit which probably supplied much of the lava that makes up the surrounding area. It is of early Palaeogene age (60 million years old - what used to be known as the Tertiary). The dolerite is quite coarse almost gabbroic in character. It stands out against the trap-featured basaltic lavas that make up the surrounding area.  It is NOT a volcano. per se. Although the walls of the plug are quite steep, there is no obvious Field Trips between it and the surrounding lavas - they seem to grade into one another.


The rock is very fresh as it lies well away from the "zone of pneumatolysis" where alteration of the rocks due to hydrothermal action has occurred. Thermal alteration of the surrounding rocks has produced some unusual minerals such as reyerite.


The summit hollow is filled with a loch (Lochan ‘S Airde Beinn) which is probably the result of glaciation. It is sometimes referred to as a crater. It isn't!

Locha S airde beinn
Lochan 'S Airde Beinn, viewed from the north top, looking south.

‘S Airde Beinn is a great viewpoint on a good day – the islands of Rum, Eigg, Skye and Ardnamurchan can easily be seen. These are also of Palaeogene age and are mainly composed of volcanic rocks.  To the west lie the islands of Coll and Tiree which are much older, being of Lewisian age (over 2000 million years old). And to the south, Mull’s highest mountain, Ben More is clearly visible

Satellite view of SAB with the Mishnish Lochs to the south. (Loch Carn an Amais, Loch a' Mheadhoin, Loch Peallach)

There are other volcanic plugs in the area. To the north, close to the Glengorm road is a prominent hill called Creag a Chrochair (The Hangmans Rock). South of 'S Airde Beinn, close to the forestry track by Loch Frisa, another two plugs can be found which display good columnar structures.  These four plugs all lie on the same rough N - S trending line.

Other photos of the location:

Click on an image to open a larger picture.

Lochan S Airde Beinn, looking north.

Lochan 'S Airde Beinn, frozen
Lochan S Airde Beinn, looking south.

Lochan 'S Airde Beinn,
Approaching S Airde Beinn from the south.

S Airde Beinn
Lochan S Airde Beinn, view to south

Lochan 'S Airde Beinn
Thin section in PPL

Thin section in PPL
Thin section in XPL

Thin section in XPL
View North to Rum and Ardnamurchan

View North
View North from North summit cairn to Meall an Inbhire (aka Cnoc Fuar) and Ardnamurchan

View North

Similar or related Geological Sites:

  1. Creag a Chrochair, Glengorm
  2. Loch Frisa plugs


JNCC Geological Conservation Review. Site Report. A very thorough description of the site.

Bailey, E.B., Clough, C.T., Wright, W.B. et al. (1924) Tertiary and Post-Tertiary Geology of Mull, Loch Aline and Oban. Memoir of the Geological Survey of Great Britain, HMSO, Edinburgh.

 Beckinsale, R.D., Pankhurst, R.J., Skelhorn, R.R. et al. (1978) Geochemistry and petrogenesis of the early Tertiary lava pile of the Isle of Mull, Scotland. Contributions to Mineralogy and Petrology, 66, 415–27.

 Cann, J.R. (1965) The metamorphism of amygdales at ’S Airde Beinn, northern Mull. Mineralogical Magazine, 34, 92–106.

Geikie, A. (1897) The Ancient Volcanoes of Great Britain. 2 vols, Macmillan, London.

Judd, J.W. (1874) The Secondary rocks of Scotland. Second Paper. On the ancient volcanoes of the Highlands and the relations of their products to the Mesozoic strata. Quarterly Journal of the Geological Society of London, 30, 220–301.