Conival Ben More Assynt

Ascent — around 1000 metres

Difficulty — very strenuous mountain walk

Duration — about 8 hours there and back

Start -— grid reference [NC 251 216]

The ascent of Conival and Ben More Assynt, the only Munros in the area, takes you into the ‘Assynt Window’, one of the widest parts of the Moine Thrust Zone, and crosses several major thrusts. This is a long mountain walk, only suitable for those with experience of walking in the hills, and with all the necessary equipment.

Start from the Inchnadamph car park, follow the main road across the river, and walk up the track past Inchnadamph Lodge and past Glenbain Cottage. After the cottage, the track turns into a footpath that is easily followed up the left (north) bank of the River Traligill. This glen is underlain mostly by outcrops of limestone, and the lower section is described in more detail in the Traligill Caves walk.

After following the river up Gleann Dubh for about 1.5 kilometres, the path turns left to climb up the peaty slopes. Just before the path leaves the river [1] [NC 28630 20461], look out for boulders of greenish rock containing large pebbles of pink and grey quartz — there is one such boulder on the path, and others scattered around. This type of rock is known as conglomerate, which is from the lowest part of the Torridonian Sandstone sequence higher up on the slopes of Ben More Assynt. The boulders are erratics, carried here by glaciers during the last ice age. From here, you have a good view of the face of Conival, which is composed entirely of quartzite. In fact, there is a thrust running across the face, along which Basal Quartzite has been pushed on top of younger Pipe Rock. You can’t see the thrust from here, but you will cross it on your way to the summit.

Climb steadily upwards on an eroded peaty path, with the rushing stream of the Allt a’ Choinne Mhill on your right hand side. If you stop for a rest, look back at the vista opening up behind you. To the south, beyond the lower slopes of Conival, is the quartzite ridge of Breabag. To the south-east, in the middle distance, is the red-capped hill of Beinn nan Cnaimhseag, which is composed of Torridonian Sandstone. In the distance, you can see more hills of Torridonian Sandstone, including the prominent triangular peak of Cùl Beag, and the quartzite-capped ridge of Canisp. In the foreground is a low peaty plateau, with narrow, green valleys cutting into the limestone bedrock.

Continuing to climb, you come across outcrops of Basal Quartzite in the path. Look closely and you may see cross-bedding, picked out by fine brown lines. Just after crossing the stream at the base of a small waterfall, you come across a metre-high step of brick-red rock [2] [NC 29728 20901]. This is a sill, or sheet of igneous rock, formed when magma (molten rock) was forced into the layers of quartzite. If you look across at the slopes of Conival, you may be able to trace this and other reddish sills that cut through the quartzites.

Higher up, the path winds up a shattered staircase of pinkish quartzite that forms an escarpment below the upper corrie. Look closely at this quartzite as you climb; the surfaces are pitted and knobbly, and vertical white lines can be seen in the faces of the rock slabs — these are traces of worm-burrows and this is the Pipe Rock, which lies above the cross-bedded Basal Quartzite seen lower down.

Above this rock staircase, the path becomes less steep as it skirts the eastern edge of a small peaty corrie. Look out for a large slab of Pipe Rock in the path that is covered by parallel scratches and grooves; these are glacial striae, formed by the scraping action of rocks frozen into the base of a moving glacier. The direction of the scratches shows that the glacier here was moving towards the south-west.

Climb over quartzite scree to the col between Conival and Beinn an Fhurain [3] [NC 30011 20955], and look into the large northern corrie (Coire a’ Mhadaidh). This corrie is walled by the quartzite ridges of Na Tuadhan on the north and Ben More Assynt on the south, but is floored by dark grey knobbly Lewisian Gneiss. Lower down in the corrie, there are moraines, mounds of debris dumped by a retreating glacier. Further out, you can see a vast expanse of peat bog stretching away to the isolated peak of Ben Klibreck in the distance. Beneath this peat lie the Moine Rocks, east of the Moine Thrust.

From the col, turn to the south (right) and take the zigzag path up the quartzite screes that cover the northern ridge of Conival. The path climbs steeply at first, then more gently along a high ridge with many prominent outcrops of quartzite [4] [NC 30075 20392]. Look closely at this quartzite — you may be surprised to see cross-bedding in many of the faces. As you have climbed, you have come back into the Basal Quartzite, which is older than the Pipe Rock at the col. The fact that older rocks are on top of younger shows that you have crossed a thrust — in this case it is the Ben More Thrust that crosses this ridge just above the col.

Continue to the stone wind-break at the summit of Conival, from where there is a stunning panorama on a clear day. From here, a long undulating ridge of frost-shattered quartzite stretches east to the summit of Ben More Assynt. The walk to this summit and back will take you about one and a half to two hours, but is well worthwhile on a clear day. The descent to the ridge from the summit of Conival is an easy scramble over cross- bedded quartzite slabs. If you look back at Conival, you can see that its southern ridge is composed of much darker rock; this is the Torridonian Sandstone, which underlies the quartzite.

Continue eastward to the lowest point of the ridge. To the south, steep slopes of quartzite scree drop into the wild Garbh Coire, with its dark loch nestling below the rocky cliffs of Ben More Assynt’s south ridge. To the north, across Coire a’ Mhadaidh, is the cliff-face of Na Tuadhan, in which the quartzite layers are folded to form a steep arch. This arch formed when the thick quartzite sheet buckled under pressure during movement on the Ben More Thrust.

Continue over quartzite knolls to reach the twin summits of Ben More Assynt [5] [NC 31813 20128]. The more northerly, true summit is a crag of coarse-grained, pebbly quartzite. It is worth walking some 50 metres past the south summit to where you find outcrops of greenish Lewisian Gneiss — this is one of the highest outcrops of this rock type in Scotland. From the summit, retrace your steps over Conival and return by the ascent route.

Figures

(Figure 83) Conival and Ben More Assynt. Painting of walk by Elizabeth Pickett.

(Figure 84) View east up the River Traligill to Conival.

(Figure 85) Glacially transported boulder of conglomerate below Conival.

(Figure 86) Cùl Mòr and Canisp from the slopes of Conival.

(Figure 87) The Allt a‘ Choinne Mhill falls over a staircase of Pipe Rock.

(Figure 88) View over Coire a’ Mhadaidh to Ben More Assynt.

(Figure 89) Ben More Assynt from Conival, with pale quartzite on the left and dark Lewisian Gneiss on the right.

(Figure 90) Na Tuadhan with its folded quartzite layers viewed from Ben More Assynt.

(Figure 91) Looking down the south ridge of Ben More Assynt.