Twll Twrw or Monk’s Cave, near Blaenplwyf

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Here the Wales Coast Path passes through land which was once farmed by monks from Strata Florida Abbey. A little to the south along the shoreline is Twll Twrw or Monk’s Cave, where a blowhole fascinated Victorian tourists. The old photos of the cave and cliffs are shown here courtesy of Ceredigion Archives.

Old photo of Twll Twrw or Monk's CaveThe farm here is named Mynachdy’r Graig. Mynachdy is Welsh for monastery. Graig means rock, and here probably refers to coastal rock features nearby. The farm was a medieval grange belonging to Strata Florida. The monks also had fishing rights along the coast.

The cliffs here are of boulder clay (see the footnotes for geological information). The sea carved the cave out of this material until it came to harder rock. The pressure of waves at the back of the cave then eroded the boulder clay upwards, forming a fissure which eventually reached the surface of the land above – thus forming a blowhole.

Old photo of cliffs around Twll TwrwWhen the tide was in, waves pushed air up the hole and the noise of the sea was broadcast from the opening at the top. It was said that local farmers used this as a barometer; if the blowhole could be heard a “great distance off” it was likely to be wet and stormy, but if visitors had to search for the opening before hearing the noise, the weather would be fair.

Twll Twrw means “hole of noise”. In Victorian times, the feature was often referred to as Thunder Hole, a dramatic approximation of the Welsh name.

This section of the coast is vulnerable to coastal erosion, which eventually caused the ground around the blowhole to collapse. The name Twll Twrw has outlasted the geological feature.

One group of visitors saw the effects of erosion when visiting the cave in 1906. They hurried out when they heard rockfall above. Some of the boulders which fell were estimated to measure 2ft square (c.2,000cm square).

With thanks to Michael Statham, of the Welsh Stone Forum

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Footnotes: Geology around Twll Twrw

The multi-layered cliffs here are comprised of boulder clay deposited by glacial activity in the last Ice Age. Behind are sandstone and mudstone rocks known as the Trefechan Formation, part of a sequence of rocks from the Silurian period called the Aberystwyth Grits Group.