The lake was formed at the end of the last Ice Age, about 15,000 years ago. It is a rare example of a lowland ogliotrophic lake (one that is poor in plant nutrients). They are usually found at high altitude. (from an information board near the Visitor Centre).
Uploaded to Geograph by Humphrey Bolton on 26 October 2016
Photo © Humphrey Bolton, 26 October 2016. Licensed for reuse under this Creative Commons licence