Pingos, an Ice Age Relic Hidden in a Corner of Rural Norfolk

Associated with the Artic and subarctic because of their icy origins and not to be confused with a children’s television programme or a game of chance, pingos are a periglacial landform described as an intra permafrost ice-cored hill that are conical in shape.

With that in mind, it’s rather surprising to discover that pingos can also be found in the UK but appear quite differently although they share the same origins as their colder cousins.


What are Pingos?

Created at the end of the last Ice Age, pingos were formed with a lump of ice like a giant mole hill. Unlike the Arctic and subarctic, the glaciers retreated and left hard layers of ice called lenses pressed into the ground and covered in soil.

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As the temperature rose, the ice melted and formed a depression, and the meltwater then created a pond in the resultant hollow.

Where is a Good Place to find Pingos?

Pingos form when groundwater or a subsurface lake freezes and expands, causing the ground to heave upwards. Image Credit: Hugh Venables

Because most pingos have been lost, usually ploughed up and absorbed into the countryside, they are quite a rare find in the UK. However, the best place to look is Breckland in Norfolk where there are multiple pingos.

Breckland is a 39,433-hectare site that actually spills over into neighbouring Suffolk.

It is an SPA, that’s a Special Protection Area under the European Union Directive on the Conservation of Wild Birds and also has 7,500 hectares designated as a Special Area of Conservation.

pingo trail
The Great Pingo Trail in the Brecks, Norfolk. Image Credit: David Pashley

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Breckland mostly comprises sandy gorse-covered heathland and one of its unique distinguishing features is the twisted Scots pine or ‘deal rows’ as they are called which characterise this unusual landscape.

D-Day Landings

One of the driest areas in England or as ‘dry as Jerusalem’ as the locals say, the area’s original habitats have been preserved and protected partly due to the influence of both of the 20th century’s world wars.

Namely the creation of Thetford Forest in 1914 and by the development in the 1940s of the Stanford Battle Area to prepare for the D-Day landings. Both of these have left large tracts of the landscape untouched.

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Despite its arid nature, Breckland is a great place to find pingos and this area has the largest concentration in the UK.

The Great Eastern Pingo Trail is a track network some eight miles in length which works its way around the eastern edge of the Breckland area and from which there are a large number of pingo ponds to visit.

Pingos can vary in size, ranging from a few meters to several tens of meters in height, and they can have a diameter of up to hundreds of meters. Image Credit: Marion Phillips

The trail owes its name in part to the former Great Eastern Railway and wends its way around the villages of Stow Bedon, Thompson, Breckles and Great Hockham and can be taken as a stand-alone walk from the Peddars Way long distance footpath.

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There are guided walks available which can provide a lot of information about the pingos and surrounding area and wildlife.

It’s a gentle walk on the level but because of the amount of water in this location and the insect life, repellent is recommended in the summer months.

The Difference between a Pingo and a Pond

Before the advent of mains water and taps in the home, man needed ponds to live and to water livestock and irrigate crops, so ponds were a feature at almost every farm and in every village.

Either spring fed or manmade, ponds became neglected as mains water developed, and they were no longer needed.

Add to this the intensification of agriculture in the middle and later years of the 20th century and many ponds were filled in and disappeared.

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Lost ponds are sometimes called ‘ghost ponds’. Fifty years ago, there were twice as many ponds across the UK as there are today.

Pingos typically occur in low-lying areas where the underlying ground is composed of a mixture of gravel, sand, and silt.

The difference between a pond and a pingo is that pingos did not ostensibly serve a useful purpose.

Created by nature and as the Great Eastern Pingo Trail will testify, not usually located near houses or within villages, because pingos were naturally occurring and not designed to serve the human population and livestock, they have survived in certain locations in decent numbers.

Ghost Pingos

Although the Brecks in mid Norfolk has a high density of pingos, these are only a fraction of what was there a few hundred years ago.

Land claimed for agriculture resulted in the destruction of many of the pingos and now Norfolk Wildlife Trust (NWT) are planning to resurrect the ‘ghost pingos’ which have disappeared in a landmark eight-million-pound project.

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The focus of the project is the edge of Thompson Common near Thetford.

map of pingos

The land is gradually being excavated using machinery and the location of the pingos identified via a distinctive layer of black peat, expert input and the assistance of old maps.

The plan is not just to restore more pingos but to unearth seeds and other organic material which can help recreate the original biodiversity present in each individual pingo.

Professor Carl Sayer

Four pingos were unearthed in 2021 at the aptly named Watering Farm but the NWT believe there could be around twenty more and are looking for the rest.

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Finding them is not as easy as it sounds, with a lot of knowhow and detective work used to establish the original locations.

Academics from University College, London including Professor Carl Sayer are involved alongside Brighton University, the Norfolk Ponds Project which is working to resurrect ghost ponds in Norfolk, and the Norfolk Geodiversity Partnership.

Archaeologists and local volunteers complete the line up. The Norfolk Ponds Project started work in 2014 with the aim of rediscovering ancient ponds and not just pingos.

So far, they have resurrected 250 lost ponds including 26 pingos on Watering Farm and as many as 40 on Mere Farm.

Small pingo in open landscape
A small pond in an area of rough grassland on the Pingo Trail.
Small pingo in open landscape. A small pond in an area of rough grassland on the Pingo Trail. Image Credit: Katy Walters 

The idea is to extend the unique habitat of the existing pingos in this area and better support wildlife by creating more space for the Breck’s native species as well as mitigate the impacts of climate change.

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To this end, the NWT has also purchased Mere Farm, a 130-acre site also on the edge of Thompson Common where it is believed there are more pingos. Thompson Common is the unofficial pingo capital of the UK!

Thompson Common is a unique survivor of the march of modern farming and the loss of many commons and pingos. The huge concentration of these ponds made the land virtually unfarmable.

However, pingos around the edges of the Common were gradually filled in and absorbed into workable farmland.

What Lives in a Pingo?

Most pingos were a similar size to your average village pond with their own habitat of marsh plants and insects which varied from pingo to pingo depending upon whether the pond was shrouded in shade from trees or out in the sunshine.

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The Emerald Damselfly is a resident of Thompson pingos, it appeared in recent years having been considered officially extinct by scientists in the 1980s.

The Great Eastern Pingo Trail
The Great Eastern Railways Thetford to Swaffham line ran past here, hence the station style sign. The pingo trail runs along part of the old trackbed. Image Credit: Ashley Dace

There are 57 other rare species in Pingoland including the northern pool frog, the UK’s rarest frog which has been reintroduced to this location in 2005, and the pond mud snail.

A guided pingo tour can help provide this information as the landscape is deliberately unspoiled and absent of visitor boards and other signage.

Norfolk Wildlife Trust intend to access the original sediment and rediscover an ancient seedbank in each pingo and have made some interesting discoveries including burnt flint and animal bones. 

There will be considerable work involved in identifying the plants and seeds which would have been present when the pingo was full of water.

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The sediment will contain species present when there were no chemical sprays or fertilisers so there is a real opportunity to discover lost plants and flora.

Pingos in Unusual Places

Pingos would have existed all across the UK but claiming land for farming and building have meant the majority of them have disappeared. However, sometimes, excavations for new projects reveal pingos in some surprising places.

The first Blackwall Tunnel in London was completed in 1897 and at the time, was the longest underwater tunnel in the world. One of the many challenges for the engineers was the unique geology of the area.

In this part of London, the surface of the bedrock is usually pretty level with variations no greater than about five metres in height but the tunnel survey revealed a deep depression at Blackwall which went down through the London clay at least sixty metres into the chalk.

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This was one of the main reasons the tunnel took six years to build. The second Blackwall Tunnel built in the 1960s met with similar problems.

Both tunnels pass through a basin which was completely filled with sand and gravel. Similar depressions have been found in other parts of London like Canning Town and Battersea and scientists believe them to be pingos.

Melting ice left a hole which was filled with the collapse of overlying deposits. The sudden release of water from the chalk aquifer deepened the hollows and explains the chalk blocks that were discovered in the gravel about fifteen metres above the chalk strata.

At the London Wetlands Centre in Barnes, there are also pingos visible. These are not ponds but small hillocks that look like giant molehills where the ice lenses have raised the ground surface.

Where does the Word ‘Pingo’ Originate from?

Pingo is the Eskimo word for hill. In the UK, pingos are also called kettle lakes. In Norfolk, due to the accent, pingo will sound more like ‘pingu’ if you ask a local for directions.

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