Monday, December 19, 2011

Ponds, marl pits and pingos

click photo to enlarge
When I moved from East Yorkshire to the Fylde Coast in Lancashire I was struck by the number of small ponds in the fields around where I lived. The geology of the area, the location of the ponds relative to field boundaries, the sheer amount, and the evidence of "spoil" at the edges of some, led me to the conclusion that they were marl pits, holes deliberately dug to find lime-rich clay to spread over a light, impoverished soil to improve its fertility and water-holding capacity. Such pits, which frequently become ponds, are common in many lowland areas of Britain. Cheshire abounds with them, though it also has large ponds the size of small lakes (meres) caused by gravel extraction or the subsidence of salt workings.

Britain's man-made ponds were also dug as watering places for cattle and sheep and perhaps some of those on the Fylde Coast were made for that reason - or served that purpose after the marl had been extracted. The period from 1750 was when many of these kinds of ponds were created. But not all field ponds are man-made. Some occur naturally where soil type and water flow lead to the build up of water. This kind of pond is often dry in high summer, but has varying levels of water at other times of year. Several of the Cheshire meres are thought to have been created thousands of years ago when glacial ice that was embedded in moraines melted. The eastern edge of the Fens and the Brecklands valleys have ponds that have been identified as pingos. These were formed during the last glaciation when ice below the surface caused mounds which collapsed when temperatures rose, creating ponds.

What of today's pond in the Fens photographed on a foggy day? It's my guess that it's man-made. In this area that was once littered with ponds and meres of varying sizes caused by the poor drainage of low-lying land there are, today, hardly any left. Agricultural improvement banished them, and with their disappearance went the wildlife that frequented them. This happened not only in the Fens but right across the country. In fact, three-quarters of our field ponds have been filled in or drained since the second world war. So, examples such as the one above are not only a worthy photographic subject, but are in need of preservation as precious ecological and scenic resources.

photograph and text (c) T. Boughen

Camera: Lumix LX3
Mode: Aperture Priority
Focal Length: 10.2mm (48mm/35mm equiv.)
F No: f4
Shutter Speed: 1/20
Exposure Compensation: -0.66 EV
Image Stabilisation: On