[meteorite-list] A Blast From Heaven? Canary ISlands

From: E. L. Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:43 2004
Message-ID: <3FD7AD8C.90407_at_epix.net>

Hello
Jose Campos wrote:

> I would like to know more about that island in the Azores (?) being
> watched for a possible massive landslide. If my memory is right, I
> think that I read (quite sometime ago, some 2 yrs ago or so), about
> something similar - but refering to one of the Canary islands - not
> the Azores?


I've been trying to locate the island location myself and yes it is in
the Canary Islands. Here is an excerpt from Science of Tsunami Hazards :
Landslides from Volcanic Islands and and Bolide produced tsunamis.
<http://sthjournal.org/203/ec1.pdf>

Elton

Landslides from Volcanic Islands:

The discovery of massive amounts of rock debris around the Hawaiian
Islands that probably resulted from
gradual or rapid collapses of portions of these islands, has stimulated
the search for similar landslide activity around
other volcanic islands. One of these island groups is the Canary
Islands, located in the eastern Atlantic, an area that
could give rise to tsunamis that might affect the east coast of the
United States. Evidence for collapses on the Canary
Islands includes a large amphitheater on the western island of La Palma.
Other amphitheaters--possible collapse
sites–are found throughout the islands. Ocean floor imagery northwest of
El Golfo (island of El Hierro) shows a huge
landslide (100 km3) extending 80 km from the island that contains blocks
as much as 1 km across. Further south a
much younger volcano appears ready to collapse at any time. (McGuire, 1999).

Collapses in the Canary Islands apparently occur when the flanks of the
volcanoes become too steep to
support themselves and slide into the sea. This mechanism for producing
landslides in the Canary Islands differs from
that which probably occurs in Hawaii. In the Canary Islands the rock
probably falls as a coherent blocks. In Hawaii,
the rock may break up and enter the ocean in the form of a disaggregated
mass. (McGuire, 1999) A solid block of
rock is more efficient in generating a large tsunami. These tsunamis
would probably be directed toward the United
States East Coast.

There is evidence that large tsunamis have been generated by these
Canary Island landslides. For example,
on the Bahamian Island of Eleuthera, boulders of coral limestone “as big
as houses and weighing thousands of tons”
have been deposited 20 m above sea-level and as much as 500 m inland. On
the other end of the Bahamas archipelago
are large sand wedges several kilometers long and up to 25 m
high–probably also formed by large waves in the area.
The estimated ages of these features in the Bahamas seem to match the
collapse at El Gulfo on the island of El Hierro
in the Canary Islands. (McGuire, 1999) Tsunamis capable of leaving such
artifacts in the Bahamas would doubtless
cause much devastation in the Caribbean and also along the East Coast of
the United States.

Bolide Impact Tsunamis:

Perhaps the least likely source of tsunamis has the potential for
causing the greatest tsunami: that of a meteor
or comet impact. While many previously scoffed at the idea of an
extra-terrestrial object hitting the earth, that has
recently changed. Models have recently shown that an asteroid hitting
the ocean can cause a large tsunami that would
inflict catastrophic damage to coastal cities even at great distances.

An ocean impact is more likely than an impact on land since the Earth is
seventy percent covered with water.
At the same time human populations and assets are largely concentrated
in coastal cities that were established
historically from shipping, and trade near ports. Searches for large
tsunamis in the geological record have begun in
the coastal areas of the Atlantic in the 1990's. Because large
earthquake-induced tsunamis are rare in the Atlantic is
likely that many of those detected in the geologic record would probably
be due to bolide collision.

Currently estimates are that an asteroid-induced tsunami exceeding 100
meters in height along the entire
Atlantic coast line probably occurs once every few thousand years, which
slightly exceeds written history in most of
these ocean coastal regions. Modeling shows that a 100 meter tsunami
would travel inland about 22 km (14 miles)
and a 200 meter tsunami would travel inland about 55 km (34 miles) Such
a tsunami would cause unprecedented
damage to now-developed low lying areas all along the United States East
Coast, and may totally submerge vast areas
in Europe such as in Holland and Denmark.

There is evidence that at least one such an impact occurred in an
Atlantic Ocean coastal area about 35 million
years ago. A crater at Chesapeake Bay, Virginia, was caused by an
asteroid or comet traveling at about 70,000 miles
(113,000 kilometers) an hour, that splashed through several hundred feet
of water and several thousand feet of mud.
Received on Wed 10 Dec 2003 06:34:36 PM PST