Comets and Asteroids - Tsunami - page 184

9.6 Historical Evidence for an Impact Event

the age of the Wandjina paintings. Based on the evidence
presented here, and because Aboriginal legends concentrate
on the three main elements of a comet impact in the ocean:
the comet itself, tsunami, and flooding rains, this tsunami
has been labeled the Wandjina event. No impact crater has
yet been found, although attempts are being made to find it.
The Wandjina event generated the biggest and most wide-
spread mega-tsunami yet found in the Australian region.
The geomorphic evidence is an order of magnitude greater
than that produced by any historic volcanic or earthquake-
generated tsunami originating from Indonesia. The 16th and
early seventeenth centuries were a period of European
exploration and trade in the region. This event must have
been observed and recorded by them. At present no record
has been found.

With the above evidence and many other legends referring
to impacts in the last 10000 years (Masse 1998 , 2007 ), it is
conceivable that there was an historical event. Baillie
( 2007 ) mentions a comet impact on September 28, 1014 that
could have been recorded historically. The comet affected
the North Atlantic region. GRIP ice core data indicate that
the highest ammonium spike within the historic period
occurs in 1014. Investigations of Comet Hale-Bopp, and
other comets, show that ammonium is a major component
(1-2 %). The Tunguska bolide in 1908 produced a high
ammonium anomaly in the GISP2 ice core data as well. The
eleventh century timing is also the second highest peak of
meteor sightings and a period of numerous comet obser-
vations in the historical record (Fig. 9.3 ). Historical records
in Britain indicate that widespread flooding took place at
this time (Haslett and Bryant 2008 ). William of Malmes-
bury in The History of the English Kings (vol. 1) states:

9.5.6 Gulf of Carpentaria

The geological stability and age of the Australian conti-
nent, plus the ancientness of Aboriginal culture favors the
preservation of tsunami evidence and associated legends.
Studies are concurrently researching other areas of the
continent including the Lower Murray River of South
Australia, the Victorian coastline and the Gulf of Car-
pentaria. Initial evidence from the latter area has been
summarized by Gusiakov et al. ( 2010 ). The Gulf of Car-
pentaria is a square marine basin on the north coast of
Australia (Fig. 9.11 a). The Gulf of Carpentaria contains
stable continental crust and is not subject to tsunamigenic
earthquakes, landslides, or volcanic eruptions. Three cores
from the Gulf of Carpentaria yielded a thin layer near the
surface containing vitreous material, magnetite spherules,
and occasional pure carbon and silicate spherules with an
age of about 1500 BP (Martos et al. 2006 ; Abbott et al.
2007a , b ). The magnetite spherules are undoubtedly
products of a terrestrial impact. Two crater candidates,
18 km and 12 km in diameter, have been found in the
southeastern Gulf (Martos et al. 2006 ). An impactor about
640 m in initial diameter could have fragmented to pro-
duce both craters. There are also chevrons oriented to
these sites on the west side of the Gulf on Groote Eylandt
and along the south coast on Van der Lin Island (Kelletat
and Scheffers 2003 ). The inferred maximum implied run-
ups of the mega tsunami are over 60 m above sea level on
Groote Island and 20 m on Van der Lin Island. Nott
( 1997 ) found anomalous aligned boulder deposits along
the south coast that he independently linked to a tsunami
event rather than any tropical cyclone. Finally, there are
Aboriginal legends and songs from Mornington Island
referring to an impact(s) event (Mornington Island Cor-
roboree Songs 1966 ).

a tidal wave, of the sort which the Greeks call euripus and we
ledo, 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'' (Mynors et al.
1998 , p. 311).

Malmesbury's subsequent chronology places this tidal
wave in 1014. Also of historical importance is The Anglo-
Saxon Chronicle, which states:

on the eve of St. Michael's Day [September 28th], 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 (Ingram 1823 ).

Some accounts suggest that this flood affected Kent,
Sussex, Hampshire (Green 1877 ), and even as far west as
Mount's Bay in Cornwall, where the Bay was ''inundated
by a 'mickle seaflood' when many towns and people were
drowned'' (Saundry 1936 ). Short ( 1749 ) reports in his list of
earthquakes that in 1014 ''in Cumberland [Cumbria on the
northwest coast of England]; much people and cattle lost''.
The flood is also mentioned in the Chronicle of Quedlin-
burg Abbey (Saxony), where it states many people died as a
result of the flood in The Netherlands (Haslett and Bryant
2008 ). And it is remembered in a North American account
by Johnson ( 1889 ).
There is geomorphic and geological evidence of a cos-
mogenic event at this time. Haslett and Bryant ( 2007 )
describe the movement of boulders, up to 193 tonnes in
size, and bedrock erosion in north Wales that is most likely
related to a mega-tsunami. Marazion Marsh, landward of
Mount's Bay, England contains a sand layer similar to those
described in Chap. 3 , which has been dated as younger than
AD 980 (Healy 1995 , 1996 ). Finally, there is evidence for