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Fig. 7.6 Aerial photograph of
the foreshores of Lituya Bay
swept by the tsunami of July 9,
1958. Source http://libraryphoto.
cr.usgs.gov/htmllib/btch132/
btch132j/btch132z/mdj01278.jpg
Slide
Maximum run-up
caused by backfilling of the depression left in the ocean by
the removal of material that formed the turbidity current. It is
difficult to attribute the wave to a single rotational slide
because hundreds were involved. However, a cluster of large
slides occurred in 600 m depth of water directly south of the
Burin Peninsula. The wave traveled at a velocity of
140 km hr -1 and was concentrated by refraction into the
coves along this coast, where 40 isolated fishing communities
were sheltered. The story in Chap. 1 refers to this wave as
sheep riding a rising mountain of water in the moonlight
(Fig. 1.1 ). The tsunami wave train reached the coast on top
of a high spring tide and surged up the steep shores as three
successive waves, destroying boats and houses and carrying
sediment into small coastal lagoons (Tuttle et al. 2004 ). The
characteristic tsunami signature of a fining-upwards sand
layer, sandwiched between peats, has been identified in the
lagoons at Taylors Bay and Lamaline. Run-up varied
between 2 and 7 m with an extreme value of 13 m elevation
at St. Lawrence. Two other waves in rapid succession fol-
lowed the first wave. Twenty-eight people died in New-
foundland. So isolated were the communities that news of the
disaster did not reach the outside world until two days later.
The tsunami was not restricted to Newfoundland (Long et al.
1989 ). The wave also radiated out from the headwall of the
slide and swept down the coast of Nova Scotia, without
killing anybody. Fortunately, by the time it reached Halifax,
the wave was only 0.5 m high. The wave also spread
throughout the North Atlantic Ocean and was measured on
tide gauges as far away as South Carolina and Portugal,
although no damage was reported (Whelan 1994 ).
The event is considered rare for this part of the North
American coast, with a recurrence interval of
1,000-35,000 years (Whelan 1994 ). However, a similar, but
smaller, event occurred in the same region in 1884. This
tsunami was also triggered by an earthquake and submarine
cables were broken. Since European settlement in North
America, three other large earthquakes along the east coast
could have generated tsunami if they had happened at sea or
triggered submarine landslides. These events occurred at
Cape Anne, Massachusetts, in 1755; Charleston, South
Carolina, in 1886; and Baffin Bay in 1934. While rare, the
Grand Banks slide illustrates that the east coast of North
America is susceptible to deadly tsunami caused by slides.
Large submarine slides are a common bathymetric feature
of the eastern continental margin of North America and the
Gulf of Mexico, and will occur again.
7.5
Geological Events
7.5.1
Hawaiian Landslides
Some of the best evidence for giant submarine landslides has
been discovered on the Hawaiian Islands using Geologic
Long-Range Inclined Asdic (GLORIA), SeaBeam, and
HMR-1 wide-swathe, side-scanning sonar systems (Lipman
et al. 1988 ; Moore et al. 1989 ; Moore et al. 1994b ). These
systems sweep a swathe 25-30 km wide and measure fea-
tures on the seabed down to 50 m in size. At least 68 major
landslides more than 20 km long have been mapped over a
 
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