Bristol Channel Boulders - No Ice Required

On 30 January 1607, around noon, the coasts of the Bristol Channel suffered from unexpectedly high floodings that broke the coastal defences in several places. Low-lying places in Devon, Somerset, Gloucestershire, and South Wales were flooded. The devastation was particularly severe on the Welsh side, extending from Laugharne in Carmarthenshire to above Chepstow in Monmouthshire. Cardiff was the most badly affected town, with the foundations of St Mary's Church destroyed. It is estimated that 2,000 or more people were drowned, houses and villages were swept away, an estimated 200 square miles (51,800 ha) of farmland inundated, and livestock destroyed,wrecking the local economy along the coasts of the Bristol Channel and Severn Estuary. https://en.wikipedia.org/wiki/1607_Bristol_Channel_floods

But there was another legacy of the flooding, thought to be a tsunami caused by an underwater earthquake, it moved boulders on the edges of the Bristol Channel.

Bryant, Edward A., and Simon K. Haslett. “Catastrophic Wave Erosion, Bristol Channel, United Kingdom: Impact of Tsunami?” The Journal of Geology 115, no. 3 (2007): 253–69. doi:10.1086/512750.

A very detailed paper which explains the positioning of many Bristol Channel boulders as tsunami relics. Calling them all glacial erratics may be simply wrong.