a frost-shattered upper headwall
b abraded lower part of headwall, with slabs and chocks
c scree/talus slope
d lochans set amid moraine ridges
e outer terminal moraine from the small Loch Lomond Stadial glacier
f disputed "protalus rampart"
Chock marks on slabs below the Fiacaill Buttress
Talus slopes below Aladdin's Buttress
Boulders forming the low ridge of the terminal moraine on the lip of the corrie
Coire an t-Sneachda
This is a classic example of a glacial corrie or cirque. In Gaelic, Coire an t-Sneachda is the 'corrie of the snows' and it deserves its title. The hollow is north facing and shaded from the sun. It receives large volumes of snow blown from the plateau when the winds swing to the southwest.
The long profile of the corrie is close to being logarithmic in its curvature, as the sketch below shows.
corrie shows many typical features. The headwall (a) is a cliff. The
structure of the granite controls the detail of the cliff face, with
buttresses in areas of widely-spaced joints and gulleys and chimneys between,
a diversity that has created many challenging climbs. This diversity also
reflects glacial and periglacial activity, with intense frost-riving above the
latest corrie glacier and plucking of the backwall behind the glacier. In the
lower parts of the headwall (b), evidence of abrasion is seen. Here
there are large, steeply inclined slabs with chock marks. The scree slope (c)
has formed since the last glacier filled the back of the corrie - it continues
to accumulate today, as shown by the blocks resting on late-lying snow banks
and the hazard to climbers of rockfalls. The lochans (d) are ponded
behind low moraines from the last glacier to occupy Coire an t-Sneachda. These
moraines are 1-3 m high and composed on large granite blocks, largely derived
from the headwall and carried on the surface of the glacier.
Until 2014, it was thought that
last glacier to occupy the corrie was during the
Loch Lomond Stadial, between 11
and 10 thousand radiocarbon years ago.
Kirkbride and others
have now provided dating evidence that the innermost moraines in this and
neighbouring cirques date from as recently as the Little Ice Age.