Making waves
The alarm clock went off and I opened the curtains just in time to see the sun rising into clear skies above the metallic-grey Dover Strait. The waves were rolling in and breaking noisily on the shingle across the seafront road, and I stared for a few minutes into the tranquil dawn. As I rubbed the sleep from my eyes, I tried to imagine what it must have been like to stand here and watch a massive wall of water approaching.
I was in Dover to do some filming with the BBC about research I had undertaken with a tsunami expert from Australia on the possibility that the shores of Britain have, in the past, experienced tsunami – not just one or two, but many over hundreds of years of British history. We suspect that tsunami have affected the coastline right around Britain, but the memory of these events has been lost, and is only now being uncovered by our rereading of historical documents and the landscape.
My companion, Dr Ted Bryant of the University of Wollongong, is the author of Tsunami: The Underrated Hazard. Unfortunately, the reality expressed in the subtitle of his book held sway (outside tsunami-prone areas) until the tragic events of Boxing Day 2004, when a pan-oceanic tsunami generated by a 9.2-magnitude earthquake off Sumatra forced people to begin taking tsunami seriously. Even the British government eventually commissioned a report on our own tsunami threat.
But how much of a threat are tsunami in Britain? Ted and I first met at a field meeting in Scotland in 1994, where we were shown sand layers that contained marine fossils deposited many kilometres inland by a mega-tsunami more than 7,000 years ago, caused by a submarine slide off Norway, now known as the Storegga Slide.
Archaeologists have uncovered occupation horizons sealed by sand carried inland by this tsunami, suggesting that Mesolithic coastal settlements were obliterated by it. Estimates suggest that the wave was around 25 metres high in the Shetland Islands, completely washing over some of them.
More recently, in 1755, a large earthquake occurred off Portugal, where the combined earthquake and tsunami caused great devastation in Lisbon, and sent tsunami waves along the African and European coasts that were still about three metres high when they reached the southwest coast of Britain. So Britain has experienced at least two tsunami events, but are they the only ones?
Estuary epiphany
Since 1994, Ted and I have collaborated on several projects, but it was a brief visit he made to the UK in 2002 that spawned our British tsunami research. Ted was speaking at a conference on catastrophes at London’s Brunel University, and afterwards, he had a few days free to visit the Severn Estuary, which is where most of my research up to then had been carried out.
We were to visit an archaeological excavation taking place in the tidal zone of the muddy estuary, but we arrived late and the high tide had submerged the excavation. As the light was good, we went to Redwick, a local church that I knew had a flood marker on it that Ted may be interested to see.
The marker on the porch is simply labelled ‘The Great Flood 1606’, an event that many believed was caused by a storm surge. The door was open, so we went in and picked up a booklet about the history of the parish. It contained a passage from a 17th-century chapbook that described the event:
‘For about nine of the morning, the same being most fayrely and brightly spred, many of the inhabitants of these countreys prepared themselves to their affayres then they might see and perceive afar off as it were in the element huge and mighty hilles of water tombling over one another in such sort as if the greatest mountains in the world had overwhelmed the lowe villages or marshy grounds. Sometimes it dazzled many of the spectators that they imagined it had bin some fogge or mist coming with great swiftness towards them and with such a smoke as if mountains were all on fire, and to the view of some it seemed as if myriads of thousands of arrows had been shot forth all at one time.’
Ted and I turned to one another in astonishment and said, almost in unison: ‘This isn’t a storm, it’s a tsunami!’
It was one of those rare ‘eureka’ moments that has since led us on a journey of discovery around the shores of Britain and beyond.
Because of the use of different calendars, the Great Flood of 1606 actually occurred on 30 January 1607. Before our research, the event was virtually forgotten, which is surprising given that around 2,000 people appear to have died, making it the worst land-based natural disaster in British history.
As well as the numerous historical documents, there was also physical evidence in the landscape of a tsunami-like event, including the deposition of sand layers in the otherwise muddy Severn Estuary sediments, the stripping out of the estuary’s fringing salt marshes, and the truncation of spurs of agricultural land, all of which had previously been linked to the early 17th century.
Warnings from history
During another field trip in September 2004, Ted and I collected data that suggested that the Bristol Channel had also been hit by a tsunami. From the analysis of unusual boulder deposits, we estimated that the wave was about four metres high at the mouth of the channel, but as it passed up the funnel of the Severn Estuary, it grew to a height of around six metres, exactly where the historical records indicate the greatest impact had been experienced.
One thing that eluded us was a trigger mechanism. We had suggested that the most likely cause was a submarine slide off the edge of the continental shelf somewhere southwest of Ireland. However, Dr Roger Musson, the head of seismology at the British Geological Survey, suggested that a known active fault zone in the same area could have been the culprit – after all, there had been an earthquake on that fault during the 1980s.
Because of the uncertainty, however, we can’t rule out a storm surge as the cause of the flood, even though there are no other historical accounts of storm damage. Tantalisingly, a professor from Cardiff University published an article in The Times in 2005 that described a second-hand report of an earthquake felt on the day of the flood. Apparently, the report came from an antiquarian book, but we haven’t been able to find the source.
While focusing on the 1607 flood, we had to ignore other historical records of possible tsunami events, so in autumn 2007, we undertook a field survey of the relevant sites.
The forgotten flood events we analysed fell into four categories. The first group occurred in the Dover Strait, an area underlain by a major thrust fault. The area regularly experiences earthquakes, such as the 4.2-magnitude tremor that occurred in Folkestone in April 2007. Previous, more intense earthquakes have led to eyewitness reports of what could be interpreted as tsunami.
For example, in December 1381, Empress Anne of Bohemia landed in Dover on her way to marry King Richard II. No sooner had her party disembarked that ‘the water was so troubled and shaken, as the like thing had not to any mans remembrance euer beene heard of: so that the ship in which the appointed queene came ouer, was terrible rent in peeces’. This event is thought by some to have been the inspiration for Chaucer’s ‘Tempest at hir Hoom-Cominge’ in The Knight’s Tale. And in May the following year, a 5.75-magnitude earthquake caused churches to collapse and generated waves that damaged ships in port and led contemporary writers to describe the event as a ‘watershake’ or ‘waterquake’. A similar earthquake revisited the area in 1580, apparently generating a tsunami that inundated Calais.
The second category of events comprise those tsunami that travelled a long distance to reach Britain. Good examples exist, such as the Lisbon tsunami of 1755, which was still three metres high when it reached the shores of southwest Britain and southern Ireland. Accounts from Lamorna Cove in Cornwall describe large granite boulders being tossed around like pebbles by the wave.
This group also includes the prehistoric tsunami that was generated by the huge Storegga undersea landslide off Norway. In total, we identified about ten tsunami events in this category.
The third group comprised local tsunami generated by earthquakes that occurred directly under the coastline. For example, we’ve interpreted eyewitness accounts associated with the April 1884 Colchester earthquake to be tsunami. The magnitude of the earthquake is uncertain, but fishermen and sailors on the Colne Estuary in Essex report their vessels rising and falling by up to a metre; those on one boat found themselves sitting in the trough of a long wave, unable to see above the wave crests on either side.
But, significantly, the Eastern Daily Press reported the next day that ‘the sea is said to have rushed with restless force over the marshes, receding some time afterwards, leaving thick deposits of sand behind, in some instances at incredible distances from the coast’. I took some cores in the estuary and found a sand layer in the marshes that could be the one being described. Taken together, these reports suggest a tsunami was created by the earthquake.
The same earthquake also appears to have generated a tsunami on the Thames in central London. Contemporary reports state that ‘a wave, estimated to have been about three feet high, was seen to cross the river, and to cause a vessel lying at St Paul’s Pier to roll heavily’.
The final event is the oldest and most controversial, but is supported by the work of other scientists. In September 1014, vast parts of the British and neighbouring European coasts were inundated by a huge flood. The flood is documented in the Anglo-Saxon Chronicles and by William of Malmesbury, who 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’.
Professor Mike Baillie of Queen’s University Belfast published a paper in 2007 that linked this flood event with the impact of a comet in the North Atlantic. His theory is supported by the occurrence of extraterrestrial chemicals in Greenland ice layers deposited at this time, and by observations made by Chinese astronomers. A model created by Dr Steven Ward, a geophysicist as the University of California, Santa Cruz, has indicated that a tsunami generated by a comet impact off western Ireland would generate flooding similar to those described in the historical records we surveyed.
Forgotten floods
These forgotten floods may not all have been tsunami, but the association of many of them with known tsunami causes, such as earthquakes and comets, does support our interpretation. Our research has examined 21 tsunami events to hit Britain over the past 1,000 years, which suggests that tsunami are a more common hazard here than previously thought.
Our research has been propelled by our view that it’s important to know if a flood is due to a tsunami or a storm, as storm flooding is more predictable and evasive action can be taken, whereas tsunami can occur at any time and require educating the public to respond quickly to warning signs. For example, people should not, when they feel an earthquake, do as a group in Kent did in April 2007, when tremors sent them rushing from their houses and onto the beach for ‘safety’.
July 2010
I was in Dover to do some filming with the BBC about research I had undertaken with a tsunami expert from Australia on the possibility that the shores of Britain have, in the past, experienced tsunami – not just one or two, but many over hundreds of years of British history. We suspect that tsunami have affected the coastline right around Britain, but the memory of these events has been lost, and is only now being uncovered by our rereading of historical documents and the landscape.
My companion, Dr Ted Bryant of the University of Wollongong, is the author of Tsunami: The Underrated Hazard. Unfortunately, the reality expressed in the subtitle of his book held sway (outside tsunami-prone areas) until the tragic events of Boxing Day 2004, when a pan-oceanic tsunami generated by a 9.2-magnitude earthquake off Sumatra forced people to begin taking tsunami seriously. Even the British government eventually commissioned a report on our own tsunami threat.
But how much of a threat are tsunami in Britain? Ted and I first met at a field meeting in Scotland in 1994, where we were shown sand layers that contained marine fossils deposited many kilometres inland by a mega-tsunami more than 7,000 years ago, caused by a submarine slide off Norway, now known as the Storegga Slide.
Archaeologists have uncovered occupation horizons sealed by sand carried inland by this tsunami, suggesting that Mesolithic coastal settlements were obliterated by it. Estimates suggest that the wave was around 25 metres high in the Shetland Islands, completely washing over some of them.
More recently, in 1755, a large earthquake occurred off Portugal, where the combined earthquake and tsunami caused great devastation in Lisbon, and sent tsunami waves along the African and European coasts that were still about three metres high when they reached the southwest coast of Britain. So Britain has experienced at least two tsunami events, but are they the only ones?
Estuary epiphany
Since 1994, Ted and I have collaborated on several projects, but it was a brief visit he made to the UK in 2002 that spawned our British tsunami research. Ted was speaking at a conference on catastrophes at London’s Brunel University, and afterwards, he had a few days free to visit the Severn Estuary, which is where most of my research up to then had been carried out.
We were to visit an archaeological excavation taking place in the tidal zone of the muddy estuary, but we arrived late and the high tide had submerged the excavation. As the light was good, we went to Redwick, a local church that I knew had a flood marker on it that Ted may be interested to see.
The marker on the porch is simply labelled ‘The Great Flood 1606’, an event that many believed was caused by a storm surge. The door was open, so we went in and picked up a booklet about the history of the parish. It contained a passage from a 17th-century chapbook that described the event:
‘For about nine of the morning, the same being most fayrely and brightly spred, many of the inhabitants of these countreys prepared themselves to their affayres then they might see and perceive afar off as it were in the element huge and mighty hilles of water tombling over one another in such sort as if the greatest mountains in the world had overwhelmed the lowe villages or marshy grounds. Sometimes it dazzled many of the spectators that they imagined it had bin some fogge or mist coming with great swiftness towards them and with such a smoke as if mountains were all on fire, and to the view of some it seemed as if myriads of thousands of arrows had been shot forth all at one time.’
Ted and I turned to one another in astonishment and said, almost in unison: ‘This isn’t a storm, it’s a tsunami!’
It was one of those rare ‘eureka’ moments that has since led us on a journey of discovery around the shores of Britain and beyond.
Because of the use of different calendars, the Great Flood of 1606 actually occurred on 30 January 1607. Before our research, the event was virtually forgotten, which is surprising given that around 2,000 people appear to have died, making it the worst land-based natural disaster in British history.
As well as the numerous historical documents, there was also physical evidence in the landscape of a tsunami-like event, including the deposition of sand layers in the otherwise muddy Severn Estuary sediments, the stripping out of the estuary’s fringing salt marshes, and the truncation of spurs of agricultural land, all of which had previously been linked to the early 17th century.
Warnings from history
During another field trip in September 2004, Ted and I collected data that suggested that the Bristol Channel had also been hit by a tsunami. From the analysis of unusual boulder deposits, we estimated that the wave was about four metres high at the mouth of the channel, but as it passed up the funnel of the Severn Estuary, it grew to a height of around six metres, exactly where the historical records indicate the greatest impact had been experienced.
One thing that eluded us was a trigger mechanism. We had suggested that the most likely cause was a submarine slide off the edge of the continental shelf somewhere southwest of Ireland. However, Dr Roger Musson, the head of seismology at the British Geological Survey, suggested that a known active fault zone in the same area could have been the culprit – after all, there had been an earthquake on that fault during the 1980s.
Because of the uncertainty, however, we can’t rule out a storm surge as the cause of the flood, even though there are no other historical accounts of storm damage. Tantalisingly, a professor from Cardiff University published an article in The Times in 2005 that described a second-hand report of an earthquake felt on the day of the flood. Apparently, the report came from an antiquarian book, but we haven’t been able to find the source.
While focusing on the 1607 flood, we had to ignore other historical records of possible tsunami events, so in autumn 2007, we undertook a field survey of the relevant sites.
The forgotten flood events we analysed fell into four categories. The first group occurred in the Dover Strait, an area underlain by a major thrust fault. The area regularly experiences earthquakes, such as the 4.2-magnitude tremor that occurred in Folkestone in April 2007. Previous, more intense earthquakes have led to eyewitness reports of what could be interpreted as tsunami.
For example, in December 1381, Empress Anne of Bohemia landed in Dover on her way to marry King Richard II. No sooner had her party disembarked that ‘the water was so troubled and shaken, as the like thing had not to any mans remembrance euer beene heard of: so that the ship in which the appointed queene came ouer, was terrible rent in peeces’. This event is thought by some to have been the inspiration for Chaucer’s ‘Tempest at hir Hoom-Cominge’ in The Knight’s Tale. And in May the following year, a 5.75-magnitude earthquake caused churches to collapse and generated waves that damaged ships in port and led contemporary writers to describe the event as a ‘watershake’ or ‘waterquake’. A similar earthquake revisited the area in 1580, apparently generating a tsunami that inundated Calais.
The second category of events comprise those tsunami that travelled a long distance to reach Britain. Good examples exist, such as the Lisbon tsunami of 1755, which was still three metres high when it reached the shores of southwest Britain and southern Ireland. Accounts from Lamorna Cove in Cornwall describe large granite boulders being tossed around like pebbles by the wave.
This group also includes the prehistoric tsunami that was generated by the huge Storegga undersea landslide off Norway. In total, we identified about ten tsunami events in this category.
The third group comprised local tsunami generated by earthquakes that occurred directly under the coastline. For example, we’ve interpreted eyewitness accounts associated with the April 1884 Colchester earthquake to be tsunami. The magnitude of the earthquake is uncertain, but fishermen and sailors on the Colne Estuary in Essex report their vessels rising and falling by up to a metre; those on one boat found themselves sitting in the trough of a long wave, unable to see above the wave crests on either side.
But, significantly, the Eastern Daily Press reported the next day that ‘the sea is said to have rushed with restless force over the marshes, receding some time afterwards, leaving thick deposits of sand behind, in some instances at incredible distances from the coast’. I took some cores in the estuary and found a sand layer in the marshes that could be the one being described. Taken together, these reports suggest a tsunami was created by the earthquake.
The same earthquake also appears to have generated a tsunami on the Thames in central London. Contemporary reports state that ‘a wave, estimated to have been about three feet high, was seen to cross the river, and to cause a vessel lying at St Paul’s Pier to roll heavily’.
The final event is the oldest and most controversial, but is supported by the work of other scientists. In September 1014, vast parts of the British and neighbouring European coasts were inundated by a huge flood. The flood is documented in the Anglo-Saxon Chronicles and by William of Malmesbury, who 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’.
Professor Mike Baillie of Queen’s University Belfast published a paper in 2007 that linked this flood event with the impact of a comet in the North Atlantic. His theory is supported by the occurrence of extraterrestrial chemicals in Greenland ice layers deposited at this time, and by observations made by Chinese astronomers. A model created by Dr Steven Ward, a geophysicist as the University of California, Santa Cruz, has indicated that a tsunami generated by a comet impact off western Ireland would generate flooding similar to those described in the historical records we surveyed.
Forgotten floods
These forgotten floods may not all have been tsunami, but the association of many of them with known tsunami causes, such as earthquakes and comets, does support our interpretation. Our research has examined 21 tsunami events to hit Britain over the past 1,000 years, which suggests that tsunami are a more common hazard here than previously thought.
Our research has been propelled by our view that it’s important to know if a flood is due to a tsunami or a storm, as storm flooding is more predictable and evasive action can be taken, whereas tsunami can occur at any time and require educating the public to respond quickly to warning signs. For example, people should not, when they feel an earthquake, do as a group in Kent did in April 2007, when tremors sent them rushing from their houses and onto the beach for ‘safety’.
July 2010
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