Tsunamis affecting Britain and Ireland are extremely uncommon, and there have only been two confirmed cases in recorded history. Meteotsunamis (displacements due to atmospheric pressure, rather than seismic shock) are somewhat more common, especially on the southern coasts of England around the English and Bristol Channels. [1] [2]
The east coast of Scotland was struck by a 21 m (70 ft) high tsunami around 6100 BC, during the Mesolithic period. The wave was caused by the massive underwater Storegga slide off Norway. The tsunami even washed over some of the Shetland Islands. Tsunamite (the deposits left by a tsunami) dating from this event can be found at various locations around the coastal areas of Scotland, and are also a tourist feature in the Montrose Basin, where there is a layer of deposited sand about 0.6 metres (2 ft) thick.
At the time, what became the east coast of England was connected to the areas of Denmark and the Netherlands by a low-lying land bridge, now known to archaeologists as Doggerland. The area is believed to have had a coastline of lagoons, marshes, mudflats, and beaches, and may have been the richest hunting, fowling, and fishing ground in Europe at the time. [3] [4] Much of this land would have been inundated by the tsunami, with a catastrophic impact on the local human population. [5]
The coast of Cornwall was hit by a 3 m (10 ft) high tsunami on 1 November 1755, at around 14:00. The waves were caused by the 1755 Lisbon earthquake. The tsunami took almost four hours to reach the UK. The tsunami was also observed along the south coast of England and on the River Thames in London. [6] Contemporary reports say that there were three of these tsunami waves, and that the sea receded very quickly, then rose up. At St Michael's Mount, the sea rose suddenly and then retired; ten minutes later, it rose 6 feet (1.8 m) very rapidly, then ebbed equally rapidly. The sea rose 8 feet (2.4 m) in Penzance and 10 feet (3.0 m) at Newlyn; the same effect was reported at St Ives and Hayle. Although there is no record of the overall death toll, the 19th-century French writer Arnold Boscowitz claimed that "great loss of life and property occurred upon the coasts of Cornwall". [7]
The tsunami also reached Galway in Ireland, at a height of 2 m (6.6 ft), and caused some serious damage to the "Spanish Arch" section of the city wall.
There are also historical records of the tsunami reaching Pembrokeshire and washing up the Cleddau estuary.
At Mount's Bay in Cornwall, a small tsunami up to 1.9 meters was observed following the 1761 Portugal earthquake. [8]
On 20 July 1929 a wave reported as being between 3.5 and 6 m (11 and 20 ft) high struck the south coast of England including busy tourist beaches at Worthing, Brighton, Hastings and Folkestone. Two people drowned and the wave was attributed to a squall line travelling along the English Channel. [9] [10]
A small tsunami in the English Channel with a peak wave height anomaly of 40 cm (16 in) occurred on 29 June 2011 affecting four counties on the south coast of England; Cornwall, Devon, Dorset and Hampshire. The tsunami was described as mild and there were no records of injuries or damage. Video footage clearly showed the tsunami and there were reports of fish leaping out the water and hair lifting up because of a static charge. [11] Initial media speculation attributed the event to an underwater landslide, as no earthquakes were recorded at the time. However, the British Geological Survey concluded that it was unlikely to have been caused by a submarine landslide and was probably a meteotsunami. [9]
Traces of a tsunami called the Garth tsunami have been reported from the Shetland Islands. [12] The tsunami took place 5,500 years ago and may be connected to the presence of mass burials on both the Shetland and Orkney islands. [13]
A widespread flood was reported in the Anglo-Saxon Chronicle to have occurred in Britain, from the coast of Cumbria to Kent, on 28 September 1014. William of Malmesbury stated that "A tidal wave... grew to an astonishing size such as the memory of man cannot parallel, so as to submerge villages many miles inland and overwhelm and drown their inhabitants." The event was also mentioned in Welsh bardic chronicles. Accounts suggest that a flood affected Kent, Sussex, Hampshire, Cumbria, and Mount's Bay in Cornwall, where the Bay was "inundated by a ‘mickle seaflood’ when many towns and people were drowned". [14] [ better source needed ]
On 6 April 1580 there was a 5.8 magnitude earthquake with its epicentre on the sea bed close to Calais. Giant waves were reported, and hundreds of people were killed when ships were sunk by the waves and the low-lying coastal land around Calais was inundated by the sea. In Dover, part of the chalk cliff collapsed, taking with it part of Dover Castle. A contemporary French account states: "in the city of Calais such a horrible and terrible earthquake came to pass that a great part of the houses fell, and even the sea overflowed into the city and did ruin and drown a great number of houses, and numerous persons perished, and a great multitude of beasts lost which were at pasture outside this city." In recent years, it has been suggested that these waves were a tsunami and not seiches. It is unlikely that the earthquake alone was strong enough to rupture the sea bed to trigger a tsunami, but it appears to have been sufficiently powerful to have caused an undersea landslide that was capable of generating a tsunami, as happened in Papua New Guinea in 1998, killing around 2,500 people.
The Bristol Channel floods are attributed to a storm surge, but some have suggested that it was a tsunami caused by an earthquake or a landslide from the Irish coast.
A tsunami was reported by witnesses in England, Germany, the Netherlands and Denmark on 5 June 1858. [15] A witness stated that at 09:15, the sea in Pegwell Bay, East Kent, "suddenly receded about 200 yards (180 m) and returned to its former position within the space of about 20 minutes". [16] The Times reported severe thunderstorms and flooding in the west of England on the same day. Due to the weather conditions, it may have been a meteotsunami.
In the 1990s, geologists realised that the Cumbre Vieja volcano in La Palma, in the Canary Islands off North Africa, could pose a tsunami risk to Britain and Ireland, as it is seemingly unstable. They concluded that a future volcanic eruption will result in the mass of rock alongside the volcanoes breaking off and falling into the sea as a massive landslide. This in turn will generate a huge tsunami, which will surge into the Atlantic Ocean and hit Spain, Portugal, the east coast of the United States, France, the southern and western parts of Ireland and the south coast of England. It is estimated that the waves will take around 6 hours to reach the British Isles, and that when they do they will be around 10 metres (30 ft) high. [17] Britain would be badly hit, and it is believed by some that if nothing is done, thousands of lives will be lost. There is considerable controversy about the accuracy of these predictions. Researchers at Delft University of Technology in the Netherlands found the island to be much more stable than was widely believed, estimating that it would take at least another 10,000 years for the island to grow enough for there to be a danger. [18]
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A tsunami is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event.
A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water.
The 1960 Valdivia earthquake and tsunami or the Great Chilean earthquake on 22 May 1960 was the most powerful earthquake ever recorded. Various studies have placed it at 9.4–9.6 on the moment magnitude scale. It occurred in the afternoon, and lasted for approximately 10 minutes. The resulting tsunamis affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, and the Aleutian Islands.
A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors, caves, and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing the formation of the standing wave.
On 26 December 2004, at 07:58:53 local time (UTC+7), a major earthquake with a magnitude of 9.1–9.3 Mw struck with an epicentre off the west coast of northern Sumatra, Indonesia. The undersea megathrust earthquake, known by the scientific community as the Sumatra–Andaman earthquake, was caused by a rupture along the fault between the Burma Plate and the Indian Plate, and reached a Mercalli intensity up to IX in some areas.
The three Storegga Slides are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated 290 km (180 mi) length of coastal shelf, with a total volume of 3,500 km3 (840 cu mi) of debris, which caused a paleotsunami in the North Atlantic Ocean.
The Bristol Channel floods of 30 January 1607 drowned many people and destroyed a large amount of farmland and livestock during a flood in the Bristol Channel area of the UK. The known tide heights, probable weather, extent and depth of flooding, and coastal flooding elsewhere in the UK on the same day all point to the cause being a storm surge rather than a tsunami.
An earthquake occurred on July 17, 2006 at 15:19:27 local time along a subduction zone off the coast of west and central Java, a large and densely populated island in the Indonesian archipelago. The shock had a moment magnitude of 7.7 and a maximum perceived intensity of IV (Light) in Jakarta, the capital and largest city of Indonesia. There were no direct effects of the earthquake's shaking due to its low intensity, and the large loss of life from the event was due to the resulting tsunami, which inundated a 300 km (190 mi) portion of the Java coast that had been unaffected by the earlier 2004 Indian Ocean earthquake and tsunami that was off the coast of Sumatra. The July 2006 earthquake was also centered in the Indian Ocean, 180 kilometers (110 mi) from the coast of Java, and had a duration of more than three minutes.
Doggerland was an area of land in Northern Europe, now submerged beneath the North Sea, that connected Britain to continental Europe. It was repeatedly exposed at various times during the Pleistocene epoch due to the lowering of sea levels during glacial periods. It was last flooded by rising sea levels around 6500–6200 BCE. The flooded land is known as the Dogger Littoral. Geological surveys have suggested that it stretched from what is now the east coast of Great Britain to what is now the Netherlands, the western coast of Germany and the Danish peninsula of Jutland. It was probably a rich habitat with human habitation in the Mesolithic period, although rising sea levels gradually reduced it to low-lying islands before its final submergence, possibly following a tsunami caused by the Storegga Slide. Doggerland was named after the Dogger Bank, which in turn was named after 17th-century Dutch fishing boats called doggers.
A teletsunami is a tsunami that originates from a distant source, defined as more than 1,000 km (620 mi) away or three hours' travel from the area of interest, sometimes travelling across an ocean. All teletsunamis have been generated by major earthquakes such as the 1755 Lisbon earthquake, 1960 Valdivia earthquake, 1964 Alaska earthquake, 2004 Indian Ocean earthquake, 2011 Tohoku earthquake, and the 2021 South Sandwich Islands earthquakes.
The Garth tsunami is a likely prehistoric tsunami off the Shetland Islands that may have occurred 5,500 years ago. Its origin is unknown; impact events, earthquakes, and submarine landslides similar to the Storegga Slide 8,100 years ago have been proposed as factors contributing to the event. Evidence suggests a run-up of more than 10 metres (33 ft) in the Shetland Islands. It probably had great impact on coastal communities in the region; mass burials dating approximately to that time in the Shetland and Orkney Islands have been interpreted to host its fatalities.
The island of La Palma in the Canary Islands is at risk of undergoing a large landslide, which could cause a tsunami in the Atlantic Ocean. Volcanic islands and volcanoes on land frequently undergo large landslides/collapses, which have been documented in Hawaii for example. A recent example is Anak Krakatau, which collapsed to cause the 2018 Sunda Strait tsunami.
The 1867 Virgin Islands earthquake and tsunami occurred on November 18, at 14.45 in the Anegada Passage about 20 km southwest of Saint Thomas, Danish West Indies. The Ms 7.5 earthquake came just 20 days after the devastating San Narciso Hurricane in the same region. Tsunamis from this earthquake were some of the highest ever recorded in the Lesser Antilles. Wave heights exceeded 10 m (33 ft) in some islands in the Lesser Antilles. The earthquake and tsunami resulted in no more than 50 fatalities, although hundreds of casualties were reported.
The 1761 Lisbon earthquake and its subsequent tsunami occurred in the north Atlantic Ocean and south of the Iberian Peninsula. This violent shock which struck just after noon on 31 March 1761, was felt across many parts of Western Europe. Its direct effects were observed even far north in Scotland and Amsterdam, and to the south in the Canary Islands of Spain. The estimated surface-wave magnitude 8.5 event was the largest in the region, and the most significant earthquake in Europe since the Great Lisbon earthquake of 1755.
On the morning of March 13, 1888, an explosion took place on Ritter Island, a small volcanic island in the Bismarck and Solomon Seas, between New Britain and Umboi Island. The explosion resulted in the collapse of most of the island and generated a tsunami with runups of up to 15 meters (49 ft) that caused damage more than 700 kilometers (430 mi) away and killed anywhere between 500 and 3,000 on neighbouring islands, including scientists and explorers. This event is the largest volcanic island sector collapse in recent history.
The devastating eruption of Oshima–Ōshima began on 18 August 1741 and ended on 1 May the next year. Eleven days into the eruption, the Kampo tsunami with estimated maximum heights of over 90 meters swept across neighboring islands in Japan and the Korean Peninsula.
The 1852 Banda Sea earthquake struck on 26 November at 07:40 local time, affecting coastal communities on the Banda Islands. It caused violent shaking lasting five minutes, and was assigned XI on the Modified Mercalli intensity scale in the Maluku Islands. A tsunami measuring up to 8 m (26 ft) slammed into the islands of Banda Neira, Saparua, Haruku and Ceram. The tsunami caused major damage, washing away many villages, ships and residents. At least 60 people were killed in the earthquake and tsunami. The earthquake had an estimated moment magnitude of 7.5 or 8.4–8.8, according to various academic studies.
The 1867 Keelung earthquake occurred off the northern coast of Taiwan on the morning of December 18 with a magnitude of 7.0. It produced strong shaking that seriously damaged the cities of Keelung and Taipei. A tsunami, thought to be the only confirmed destructive of its kind in Taiwan, drowned hundreds and had a run-up exceeding 15 m (49 ft). The total death toll was estimated to be 580 while more than 100 were injured. It was followed by aftershocks that were felt on average ten times a day.
A paleotsunami is a tsunami that occurs prior to written history where there are no documented observations. Paleotsunamis are evidenced by modern technology and scientific research. One of the largest was a megatsunami resulting from the asteroid that wiped out the dinosaurs.