Glacial - Geology
Richards Mountain Pages

The glacier above is in Iceland. Once upon a time there were similar ones in Britain, but they have long since shrivelled to a couple of semi permanent patches of snow no bigger than a tennis court. We know the glaciers were here because they left some tell tale signs - and thats what this page is all about.
Ice doesn't really do much to create new rocks, so the background to this page, is a heavily muted scanned in piece of schist. Schist is formed by heat and pressure in the Earth.

U-Shaped Valleys
Britain has encountered several ice ages. The ice sheets have at some time covered most of the country. Almost anywhere in the North or West you'll find U-shaped valleys carved by glaciers. The most dramatic examples I know of are:

• The Lairig Ghru a 2000 foot deep trough which cuts right through the heart of the Cairngorms. This is best viewed from Aviemore station, or in close up by walking from the Aviemore Ski centre, through to the other side of the Charlamain Gap. The Devils Point offers a pretty good view from the other end.
• The Honister Pass lies at the quieter side of the Lake District. A road runs through it, but the cars are utterly dwarfed by the granduer.
• For those in the South, the view South from the Gospel Pass in the Brecon Beacons offers a more modest example.

Aretes
The mountain areas of Briatin boast some fine examples of aretes. An arete is a narrow ridge caused by glaciers on both sides scraping away the rest of the mountain side. For some really good examples try:

• The Carn Mor Dearg Arete connecting the mountain of Carn Mor Dearg with Ben Nevis on a fine airy ridge. Carn Mor Dearg itself has been eroded to a triangular pyramid with the help of ice.
• The Cuillin Ridge on the Isle of Skye is perhaps the most fearsome example, though it is more a product of volcanic activity than glaciation.
• The Snowdon Horseshoe has a couple of sharp ridges - the Crib Goch, and the ridge from Y LLewidd
• Sharp Edge, Striding Edge and Swirral Edge in the Lake District are also good sharp ridges, though none of these run between mountains.

Corries and Cwms
These are the little bowls of rock on the mountainside from where glaciers start. These days they tend to have a round pool of water in instead. There are loads of these all over highland Britain...

• Red Tarn nestling beside Helvellyn in the Lake District is probably the most well known.
• Llyn Cau below Cadair Idris in Snowdonia appears in a painting in the National Gallery.
• Lochan Uaineis tucked away in an awkward to get to spot between the Angels Peak and Cairn Toul in the Cairngorms
• Lochan Nam Miseag below Sgurr An Lubhair is a stunning shallow pool that reflects the craggy peak of Stob Ban.

Moraines
These are the dumps of debris left behind by glaciers. Obviously there are no glaciers in Britain today, but in the past they covered much of the country more than once. Much of East Anglia is sediment left behind by the action of glaciers. If you look closely at the map, you'll find a ridge of low hills along the North Norfolk coast. These are the remains of a moraine left by the last ice sheet.

Erratics
More evidence of glaciation comes from erratic boulders. These are large rocks that have been carried by the ice and dumped. Although the Lakes has Bowder Stone and plenty of other examples, the most convincing ones I've come across have been on the limestone plateau to the East of The Lake District - simply because the boulders are granite. Limestone and Granite are not normally found together. example

back to the Rockery