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Little Hallingbury


Cwm Idwal

Whenever we get the opportunity, we will visit the stunning Llyn Idwal (a lake) and Cwm Idwal (the hanging valley in which it lies). On the other side of the lake we will see the impressive Idwal Slabs and the Devil’s Kitchen, a favourite rock climbing site.  

Cwm Idwal was voted one of the 7 Natural Wonders of Britain. It is a hanging valley, containing a lake (Llyn Idwal), in the Glyders (a range of mountains in Snowdonia).


       On its south side, the north-facing aspect of the ‘Devil’s Kitchen’ towers over the lake. Rock climbers use the ‘Idwal Slabs’ for a challenge.


       You can see the way the rocks have been folded over millions of years. This is called a ‘syncline’ – the younger rocks are at the centre of the fold.


       The rocks are a mixture of ‘volcanic’ rock (formed from magma erupting from a volcano) and ‘sedimentary’ rock (formed by deposition of materials over millions of years). The sedimentary rock was laid down nearly 500 million years ago (during the ‘Ordovician’ period), when Snowdonia would have been the bed of a shallow sea.

What is a ‘cwm’?


Cwm Idwal is an example of a ‘cwm’. This is a Welsh word for a type of ‘hanging valley’. The geological word is a ‘cirque’ (pronounced ‘serk’). In Scotland these valleys are called ‘corries’.

Cirques are bowl or cup-shaped valleys which have been eroded by the head of a glacier in the past.
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