The path of the 1824 bog burst from Stanbury Bog into Ponden Clough. The river of peat and boulders was up to five metres deep and was eventually ten kilometres long. The potential for a similar huge peat slide from the Sandy Moor section of the Option B access road to Calderdale Energy Park is shown. Thousands of 30-tonne tippers carrying crushed stone must come up this zig-zag track, followed by hundreds of abnormal loads of between 100 and 300 tonnes. The sideways traverse across the convex slope of Sandy Hill Moor is the most dangerous thing a track on deep peat can do. Off-piste skiers are killed every year in avalanches caused by their own weight as they traverse convex slopes like this. Map: WTRG

The site of Calderdale Energy Park between Burnley and Bradford. Map: WTRG On 2 September 1824, in a powerful rainstorm, Stanbury Bog burst, and a vast river of peat, water and boulders accelerated down Ponden Clough and charged past Ponden Hall. This blog will show in photographs the track of the 1824 bog burst. Anne (4) and Emily Brontë (6) had walked five miles from home when the bog exploded with such force that the bang was heard in Leeds. Their father Patrick heard it in Haworth and had to see out the storm at the Parsonage, not knowing if his young children would return from the moor with their helpers Nancy and Sarah Gerrs. Reverend Brontë based his next sermon in Haworth on this earthquake. “A rapid torrent of mud and water issued forth, varying from twenty to thirty yards in width and four to five in depth; which, in its course for six or seven miles, entirely threw down or made breaches in several stone and wooden bridges – uprooted trees – laid prostrate walls – and gave many other awful proofs, that, in the hand of Omnipotence, it was an irresistible instrument to execute his justice. Sometimes, God produces earthquakes as awful monitors to turn sinners from the error of their ways, and as solemn forerunners of that last and greatest day, when the universal frame of nature shall tremble, and break and dissolve.”

Hidden away near Ponden Kirk in the path of the Bog Burst is this carving: Emily Jane Brontë, August 20. 1835. Photo: John Page

Ponden Kirk is the rock buttress on the right. Raven Rock is on the bend in the Ponden Clough Beck on the left. The 1824 Bog Burst poured into this very steep natural amphitheatre and accelerated. Photo: John Page

The source of the bog burst. Looking south-east across Stanbury Bog towards Alcomden Stones on the horizon. This is exactly the same terrain that is at the top of Sandy Hill Moor. Photo: John Page

In 2025 we have had the driest Spring on record, and despite the Walshaw Moor Estate’s drainage schemes, Stanbury Bog still lives up to its name. It remains highly unstable and no paths have been established by walkers. Photo: John Page

The local geology is sedimentary, laid down in a shallow sea over 300 million years ago. It is in flat layers, like this like this wall. The wet and heavy peat has formed on top of the flat rock. The dividing line between the peat and the bed-rock sandstone is the shear plane and when it breaks on a convex slope the peat accelerates rapidly, and the terrain focuses the tidal wave into a wall of peat, water and boulders. Photo John Page

Looking across to Watersheddles Reservoir, from the edge of Middle Moor Flat over the possible route of the 1824 mudslide. Photo John Page

The torrent was up to five metres deep and large boulders were picked up and hurled through the air. The devastation can still be seen on the cratered moors today. For weeks afterwards, the Worth was full of dead fish. Ann Dinsdale, Principal Curator at the Brontë Parsonage Museum, narrates a short film of the event.

 

An 1824 Bog Burst crater. Photo: John Page

This huge boulder was carried here in the bog burst. Photo: John Page

The following year in 1825 The Edinburgh Journal of Science published an academic article by David Brewster : Notice of the Rare Atmospheric Phenomenon 1824 in which reference is made to the bog burst.

“Reports from Kelso, Berwick, Belford, Newcastle, and many places in Yorkshire and Northumberland, give accounts of a most alarming storm of thunder and lightning having occurred, accompanied with a’ vast quantity of rain, and spreading destruction over a great extent of the country.—Many men and domestic animals were killed by the lightning. It was during this storm that the subterraneous bog burst at Keighley in Yorkshire, which may be traced to the vast torrents of rain that seem to have accompanied the contemporaneous storm.”

Prior to the bog burst a period of high temperatures and dry conditions were followed by several days of exceptionally heavy rain. This would have led to a very large build-up of water in a dry Stanbury Bog, creating extremely unstable conditions in the deep peat overlaying the sedimentary bedrock. A slippery shear plane formed between the contrasting peat and sandstone, causing the the deep peat to slide down the convex slope. The mudslide would flow north-easterly under gravity into the steep sided valley of the Ponden Clough Beck. Fortunately there was no reservoir in 1824, for the force of the bog burst would have destroyed the dam, adding the reservoir’s water to a murderous torrent heading for Haworth.

Bog bursts are not uncommon. A lot of academic research has been done in recent years on them, and they are often caused by wind farm construction. The Irish Peatland Conservation Council wrote this:

“Bog bursts” or peat flows are a dramatic form of peat erosion. Sections of peat on sloped areas can break off from the main body of a blanket bog and flow down-slope, similar to a volcanic lava flow. Bog bursts usually happen after heavy rain on sites which have been put under human pressures, such as overgrazing, turf cutting or wind farm construction. For example, the construction of a wind farm at Derry Brien, county Galway resulted in a large bog burst causing almost half a square km of blanket bog to travel 2.5 km (Lindsay and Bragg, 2005). During a bog burst it is thought that the living plant layer of the bog tears due to stress and the very wet peat centre flows under the influence of gravity. Other bog bursts have been recorded in Ben Gorm in Connemara, on Clare Island in Co. Mayo and 52 separate bog bursts were recorded at Pollatomish, Co. Mayo”.

Film was taken of a small peat slide on relatively flat ground, caused by construction of Viking WF on Shetland.

Given that CWF Ltd presented such an unfinished proposal at their public consultation, we can have no confidence at all that any thought has gone into the potential for catastrophic peat slides on the north side of CEP.

The crest of the convex slope where Stanbury Bog begins to get steeper, dropping down into the Worth Valley. The boulder is not a glacial erratic, but was brought by the bog burst. Photo: John Page This history and geology of the 1824 bog burst is crucial for CEP because there are exactly the same geomorphological conditions to the north of Crow Hill Wague, in the catchment of the headwaters of the unnamed streams which flow down to Watersheddles Reservoir. This is where the Option B new road would go. A repeat of the September 1824 bog burst towards the top of the convex Sandy Hill Moor slope would wash away the new road, and fan out over Steeple Hill to clog up the small gorge leading into Watersheddles Reservoir, and Nan Hole Clough. If the bog burst were to follow the Nan Hole Clough valley then Wycoller could be destroyed.

These hummocks and groughs on the crest between Stanbury Bog and Bracken Hill are evidence of current instability in the peat mass. Photo: John Page © JOHN PAGE (WTRG)