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The Hell of High Water: Tsunami and the Cornish Coast.
 

The Hell of High Water: Tsunami and the Cornish Coast.

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Invited lecture by Professor Simon Haslett at University College, Falmouth on Tuesday 28th September 2010. Simon Haslett is Professor of Physical Geography.

Invited lecture by Professor Simon Haslett at University College, Falmouth on Tuesday 28th September 2010. Simon Haslett is Professor of Physical Geography.

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  • Ok interesting. I guess the post glaciation Sacandinavian uplift / shelf steepening also plays its part. I was interested because I've done some work up on Ormen Lange in the days when Norske Hydro were active there. There was at one point concern over shelf stability and the consequences for the safety of large gravity structures resting on the seabed. We were particularly looking for gas in the marine sediments due to its well documented effect in reducing soil strengths - particularly near faulting events where gas migration can preferentially occur. Interest / concerns were also high in 2006 as I recall, when a particularly stormy winter resulted in extreme waves in the Haltenbank area - known for its rogue waves, reportedly to some 26metres (luckily I didn't see those) resulting in cyclic loading of the seabed and consquent increases in sediment pore pressures. At that time two gravity structures in Norway experienced settling due, it was thought, at least in part to this. Its a while ago now, and I haven't heard of further concerns, but was interested because at the time there was talk of mass slope failure and consequent tsunamis. Thanks for the reply - most interesting! Ben
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  • The general thinking is that these types of massive submarine slides, like Storegga, are triggered shortly after deglaciation when sea-level rises to cover the continental shelf and increasing overburden water triggers a slide. Given that sea-level has been reasonably stable for the past 5-6,000 years, it is considered that most shelf-edge sediments would have slipped by now if they were unstable. However, current and future rising sea-level due to climate change and seismic activity do present a risk as a potential trigger for future events. Also, in the North Atlantic melting Greenland ice might also trigger seismic activity due to ice unloading, which has the potential to generate North Atlantic tsunami. I'd be interested to learn more about your own surveys.
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  • I'd be interested to hear why the Storegga slide is not considered to be a threat anymore - not disagreeing but having surveyed it a few times its still characterised by lots of growth faults and unstable sediments.
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    The Hell of High Water: Tsunami and the Cornish Coast. The Hell of High Water: Tsunami and the Cornish Coast. Presentation Transcript

    • The Hell of High Water:Tsunami and the Cornish Coast.
      Professor Simon K. Haslett
      University of Wales, Newport
      Presentation on 28th September 2010
      at University College Falmouth
    • From McGuire (2005, New Scientist)
    • From Allen & Haslett (2002)
    • Somerset Levels from Brean Down.
    • Evidence of the 1607 flood 1
      Contemporary historic pamphlets giving the:
      date (20th Jan 1606 = 30th Jan 1607)
      timing (“about nine in the morning” in Somerset)
      details of damage (2000 deaths and great economic loss).
    • Burnham 1607 tides (HW at 8.28am)
    • Evidence of the 1607 flood 2
      Commemorative plaques and inscriptions in/on churches in South Wales and Somerset.
    • Tsunami theory for the 1607 flood
      Some contradictory meteorological reports
      e.g. “a violent sea wind” (Camden, 1607) vs. “the morning … so fayrely and brightly spred” (Harleian Miscellany, 1607).
      Descriptions of a “wave” reminiscent of a tsunami rather than a storm e.g. “wave’s furie”.
      Extract from God’s warning to his people of England
    • Extracts from Lamentable Newes out of Monmouthshire
      Wave velocity
      Inland Penetration
      There is an extract from St. Uny’s Church that “a great influx of sand might have happened at Hayle” during the 1607 event.
    • Sampling sand layers
    • Measuring boulder dimensions
    • 1607 Earthquake hypothesis
      Prof Michael Disney (Cardiff University) published in The Times(5th Jan 2005):
      “The sky was blue, the tide was high, there is a second-hand report of an earth tremor felt earlier that morning”.
      Local seismic activity (earthquakes) in Feb and May 1607.
    • GEBCO Bathymetry
    • Other British tsunami?
      33 other possible UK tsunami-like events
      12 recorded in Cornwall!
    • 28th September 1014
      Accounts suggest that a flood affected Kent, Sussex, Hampshire, Cumbria, and Mount’s Bay in Cornwall, where the Bay was “inundated by a ‘mickleseaflood’ when many towns and people were drowned”.
      Marazion Marsh
    • 28th September 1014
      William of Malmesbury in The History of the English Kings (vol. 1) states 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 Anglo-Saxon Chronicle states that “on the eve of St. Michael’s Day [28th September], came the great sea-flood, which spread wide over this land, and ran so far up as it never did before, overwhelming many towns, and an innumerable multitude of people”
    • 28th September 1014
      Baillie (2007) considers this flood to have been a tsunami caused by a comet impact.
      Ice core data indicates that the highest ammonium spike within the historic period occurs in 1014.
    • 28th September 1014
      Baillie (2007) cites Chinese astronomy in support of comet (debris?) impact.
      In Nova Scotia, Micmac legends include reference to possible comet impacts.
    • 28th September 1014
      Tsunami models show it is possible that a large tsunami would be able to wrap around the British Isles, affecting Cumbria, Cornwall and English Channel.
      Dr Steven Ward (UCSC) has produced animated impact tsunami models of the Atlantic and around the British Isles.
      http://www.youtube.com/watch?v=4hQqp2JxBM8
    • Lisbon tsunami 1755
    • Documented sites in Southwest
      Mount’s Bay – arrival of 4 tsunami over 2 hours (<3m high).
      Stonehouse Creek (Plymouth) – sand sheets deposited.
      Lamorna Cove – boulders tossed around like pebbles.
      Big Pool, St. Agnes – sand sheet deposited.
    • Stonehouse Creek, Plymouth
    • Lamorna Cove
    • Big Pool, St. Agnes
    • 19th Century Tsunami
      23 May 1842 – after an earthquake felt in the Scillies , several waves <2m high came ashore in Mount’s Bay creating “a very extraordinary commotion of the sea”.
      18 August 1892 – after an earthquake felt from South Wales to the Scillies, “there was a rapid rise in the River Fowey as a great tidal wave”.
    • Future Risk
      http://www.youtube.com/watch?v=AnyxZQ8JVlM