Cwm Idwal Page 2 of 2   Geology and Ecology of Cwm Idwal The geological interest of Cwm Idwal lies in the different rock types found in the area. Much of the rocks are of hard, acidic rhyolite, which forms most of the rock in the bowl of the cwm. Higher up on the edge of the cwm are some areas of slates. Less acidic rocks enter the cwm from Twll Du (Devil's Kitchen), a dark cleft in the centre of the cliffs surrounding the cwm; the cliffs of Twll Du, and boulders and rocks on the scree below the cliffs are formed of basalt - a lime-rich rock. You can see folded rock layers in these cliffs. There are also areas of glacial moraines deposited in places around the cwm which tend to be fairly acidic. Sketch of Cwm Idwal showing the main rock types Much of the interesting vegetation and ecology in Cwm Idwal can be related to the geology as well as to pressures exerted by animals and humans. The north-facing aspect of the cwm makes it cold and allows arctic-alpine species to grow on rock ledges and cliffs. Cwm Idwal is very heavily used for recreation and you will notice signs of footpath management along the nature trail. There are sheep and feral goats within the nature reserve. Although the weather and topographical features of the area are similar within the cwm, there is a rich variety of different plant communities. Careful observations of the differences in abiotic and biotic conditions in these communities allows understanding of the factors determining the development of each distinct type of vegetation. This type of observation may be carried out by careful field measurements or by more informal observations in the field. Animals and birds found here include feral goats, wheatears, meadow pipits, peregrine falcons and ring ouzels. | 1 | 2 | Page 1 of 2