May 31, 1811 Tsunami: Southwest England, United Kingdom

the sea rose on all the southern coasts of Cornwall as well as in Plymouth, from four to eight feet perpendicularly as mentioned in the Royal Cornwall Gazette published seven days afterwards; and Mr. Luke Howard states that at Plymouth it began at 3 a.m., and continued until 10 – that at 6 45 the sea rose eleven feet (reference #3946)

At around 3 a.m. on May 31, 1811, according to several English sources, the sea seemed to convulse violently. Along the coasts of Cornwall (Marazion) and Devon (Plymouth) in particular, the sea receded abruptly, leaving all the boats in the Plymouth harbor high and dry almost instantly. About half an hour later, a huge wave 9 to 11 feet high (2.70 m to 3.30 m) struck with a terrifying roar, setting the boats and ships afloat and causing them to crash violently into one another. This sudden rise was soon followed by another equally significant retreat of the sea, once again leaving the boats high and dry. Then, around 7 a.m. that same day, a second wave 7 feet (2.10 m) high struck Plymouth Harbor again, and the sea then receded once more. Finally, a third wave, 4 feet (1.20 m) high, struck Plymouth once more. In Whitehaven, in the county of Cumbria (Great Britain), on the east coast of the Irish Sea, a news report from the same day also mentions an event of the same nature. On May 31, 1811, around 6 a.m., the port of Whitehaven was suddenly flooded by a surge of seawater that rose abruptly to a height of 1.5 feet (0.45 m) and then receded just as quickly. This phenomenon was observed four or five times that same day, with the sea movements even causing the mooring lines of several ships in the harbor to break (Figure 8). Based on current knowledge, we do not know what could have caused this event. (reference #14343)

Dawson et al., (2000) note reports from Plymouth recording sudden rises and falls with an amplitude of 4 to 8 feet (1.2 to 2.4m) over a period of four hours from 3am, with further affects at 9am. […] Milne (1844) notes that the event coincided with a period of gales and low pressure. Therefore the event is likely to have been storm induced. This is considered a non-tsunami event. (reference #14326)