For the last few years, Ellesmere College Geography department have used me for an A level glaciation field trip for their Lower Sixth form students. Having looked around for venues within realistic striking distance from Shropshire, none have matched up to what Cwm Idwal in Snowdonia has to offer. With many glacial features on obvious display, and within a relatively short walking distance from the road, it’s hard to beat.
Last year, the cwm had quite a lot of snow in it. It created more of a glacial feel to the place, but made it more difficult to see some of the features. This year was very different, with lots of sun and clear skies.
After the initial walk in to the cwm, and the outlet from the lake, we started our exploration with a chat about Charles Darwin’s visits here from Shrewsbury and the 3 ‘erratic’ rocks that made him start to ponder about the glacial history of this beautiful place. Having walked to the back of the cwm, we looked at features such as the syncline and the steep bedding planes visible on the Idwal Slabs – now popular with rock climbers. The diffluent col at the head of the steep back wall, where it’s believed that ice from the other side of the mountain flowed over this low point and into Cwm Idwal, is another fascinating feature with a lot of rock fall still obviously evident. The tarn, now distorted by various moraines and sediment, also has an alluvial fan off the back wall.
At the front of the cwm, you can see roche moutonnees, with evident striations and plucking. From here, you can also see the U Shaped valley of the Ogwen Valley leading to a rock step and the deeper glacial trough of the Nant Ffrancon. There’s also the arete and truncated spur of the Y Gribin ridge, and the ribbon lake of Llyn Ogwen.
To have so much in a small space makes this a fantastic venue for these trips, and helps to give the students a better sense of scale, rather than simply pictures from a text book.