The Bone Caves

Ascent — about 200 metres

Difficulty — up a valley on a fairly good path, with one short steep climb

Duration — 1.5 – 2 hours there and back

Start — grid reference [NC 253 179]

This walk takes you up the beautiful limestone valley of the Allt nan Uamh (Burn of the Caves) to the famous Bone Caves, where the bones of bears, reindeer and wolves that once roamed this part of the country have been discovered. The whole walk is about four kilometres long and is mostly on a good path. The walk is suitable for families — but take warm clothing and wear good boots, as the weather can change rapidly in the hills. Be careful on the final climb up to the caves where the trail crosses a steep slope.

Start from the Allt nan Uamh car park, about four kilometres south of Inchnadamph, and walk up the path, which passes a fish farm. In about 200 metres you come to an attractive little waterfall with a birch tree overhanging it [1] [NC 25579 17948]. This waterfall is here because a sill of igneous rock has baked and hardened the Salterella Grits in the river. The dark grey igneous rock, which was formed when magma was intruded into the older sedimentary rocks, can be seen at the outflow of the pool below the waterfall.

Walk up the valley, passing crags of pale cream-coloured Durness Limestone on the left. The limestone is typically covered in a green, grassy sward with a rich flora that includes mountain avens, yellow saxifrage, and lady’s mantle, making the rock type easy for geologists and botanists alike to identify! This is good grazing land, and the remains of many shielings — huts that were used by people tending their animals during the summer — can be seen along the valley. Nowadays, deer are more common in the valley than sheep or cattle.

About 800 metres from the car park, you reach a small limestone crag immediately to the left of the path [2] [NC 26046 17721], and the first view of Creag nan Uamh (Crag of the Caves) appears before you. This stretch of the Allt nan Uamh runs through a V-shaped river valley. Stop to look at the river in front of you. Most of the water doesn’t flow from higher up the valley as you might expect — instead, it is appearing from beneath your feet, at the base of the limestone crag. This is a major spring, the Fuaran Allt nan Uamh. The limestone in this area is so permeable that the water flows through it in a series of caves and fissures, only appearing at the surface at a few points. The water emerging here entered the underground system about a kilometre higher up this valley.

The river bed above the spring is dry, except during periods of heavy rain, when the underground ‘plumbing’ system can’t take all the water and it flows on the surface. Just imagine how much water must have flowed in order to carry the large blocks in the river! Rain also loosens rocks from the crags on the valley sides, and this debris is channelled down gullies to form cone-shaped piles of loose rock at the base of the slopes.

About 500 metres beyond the spring, where the valley opens out, the path forks [3] [NC 26386 17323]. Bear right, cross the dry stream bed and climb up to the Bone Caves. There are four caves in the shadow of Creag nan Uamh [4] [NC 26874 17011]. They formed thousands of years ago, before the last ice age, as water gradually dissolved the limestone along cracks and fissures. The caves here are only shallow and are the remains of a larger cave system that extended over a wide area. Over thousands of years, the valley has gradually deepened, cutting away part of the cave system, and leaving the caves we see today high and dry on the valley side.

Excavations have unearthed the bones of wolves, bears, lynxes and arctic foxes that took refuge in these caves when Scotland’s climate was much colder than it is now. Reindeer bones and antlers have also been found, but reindeer are unlikely to have entered the caves, and so it is unclear how these remains accumulated. Human artefacts and bones have been found in the caves, but very few have been dated. However, the discovery of a 2000 year old walrus ivory pin in one of the caves tells us that people were here by the Iron Age (~700 BC to AD 500). The caves are now an SSSI, so please do not dig into the floor.

People have continued to visit the caves until the present day. As one of the few limestone districts in Scotland, this valley is extremely popular with cavers. The Bone Caves themselves do not extend far into the hillside, but the entrance to the longest cave system in Scotland, the Uamh an Claonaite, is nearby.

Across the valley from the caves you can see red-brown sandstone forming small crags at the top of the hill. This is Torridonian Sandstone, twice as old as the limestone below. The presence of older rocks on top of younger tells us that a thrust has pushed the Torridonian Sandstone over the limestone. The thrust itself is not visible, as it is covered by scree and by a large landslide.

From the caves, follow the narrow path that continues east beneath the limestone crags, with an excellent view of the quartzite ridge of Breabag in front of you. This path drops down, crosses the often flooded dry river via stepping stones and then follows the river back down the valley. Join the main path again at the fork.

Figures

(Figure 23) Allt nan Uamh valley and Bone Caves. Painting of walk by Elizabeth Pickett.

(Figure 24) Waterfall in the Allt nan Uamh, formed where a sill of igneous rock crosses the valley.

(Figure 25) Yellow saxifrage on limestone.

(Figure 26) Fuaran Allt nan Uamh — a major spring.

(Figure 27) View up the dry river bed to Creag nan Uamh.

(Figure 28) Limestone debris cone on the northern side of the valley.

(Figure 29) The Bone Caves.

(Figure 30) Bear.

(Figure 31) Wolf.

(Figure 32) Landslide derived from Torridonian Sandstone across the valley from the caves.