Kettle holes are small lakes formed by the melting of hard lenses of ice that were left behind after the last ice age. So the ice was left in a lump in the frozen earth, and usually also covered in earth to form a hill. These still exist in permafrost areas, like northern Canada, (the search for pingos threw up the wonderfully named Tuktoyaktuk pingos) but I thought pingos were ice age ponds… so I got confused.
The kettle hole is what is left behind when the ice under a pingo melts. One of the characteristics of them is fairly steep sides and flat bottoms, since the action of the glacier erodes them that way. There’s a very nice project here talking about them and their biodiversity – thank you, Padeswood Biodiversity Park for the diagram above.
So when the Norfolk Wildlife Trust is talking about pingo ponds, it means kettle holes. And the pingo ponds in Norfolks Brecklands are a very rare type of habitat. Consequently, having realised that, there is a good deal of conservation work going on to protect them and their wildlife, and educate people about them.
There is an 8 mile trail around the pingo ponds, and you can start at a number of points, as well as the official start and end car park. I suppose it helps to read the notices.
Anywhere that is or has been glaciated can have kettle holes – they are fairly common in Canada, Scotland, and New Zealand, for example, and I could even see them in Svalbard if I went back in summer.
Pictures from Norfolk Wildlife Trust (norfolkwildlifetrust.org.uk)