[meteorite-list] LANL: Meteor Could Cause Big Tsunami

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Wed Jan 12 11:00:59 2005
Message-ID: <41E5492C.9C0A0AAB_at_bhil.com>

Hi,

    The graphs in "Tsunami Generated by Small Asteroid
Impacts" by Hills,
Nemchinov, Popov, and Teterev in the UofA Press
collection "Hazards Due To
Comets and Asteroids" (1994) show that for a 800 meter
soft stone object
impacting in Atlantic deep water at 20 km/sec (average
velocity for an
impactor), the height of the ocean wave 1000 kilometers
away from the point of
impact would be 100 meters. Upon reaching the shallows
which surround Florida,
the run-up height would increase to approximately 1000
meters (one full order of
magnitude).
    Yes, friends, that's one full kilometer of water. I
think that would make it
all the way cross the peninsula, don't you? I believe
that hill near Micanopy is
about 95 meters high, which leaves lots of room (905
meters) for water overhead!

    An 800 meter iron meteorite in the same place, same
velocity, would produce
a water wave of 340 meters, ramping up to a 3400 meter
wave on shore. That's a
wave over two miles high! Hello, Atlanta! Hello,
Memphis! Hello, Houston! Heck,
I'm only 447 feet above sea level here in Illinois! How
high did you say Denver
was?
    Let's say the models are off by a factor of two, or
four or even ten; it's
still Goodbye, Florida!
    Actually, Chris is right; there is on-going dispute
about impact tsunami
models. The dispute originates in the fact that it is
difficult to find
geological evidence for the very large scale tsunamis
predicted for impacts that
must have geologically frequent, hence suspicions have
arisen that the models
are exaggerated. On the other hand, what are the
geological evidences of really
ancient tsunamis and how easy to find would they be?
    I recall reading many years ago an account of using
steam hoses to excavate
a layer at a site in Alaska in which flora and fauna
were churned up together,
mammoths and tree trunks, all jumbled and squashed in a
tangled mass, and the
author wondering what could have caused it, earthquake,
landslide? All of a
sudden it sounds a lot like a tsunami to me. In fact, I
recall a number of
fossil sites where remains are jumbled and compressed
and the investigators
always attribute it to "flash floods" or "landslides."
Hmmm.
    Would a Florida tsunami only 330 feet high feel much
better to a person than
a Florida tsunami 3300 feet high, if it was just you
standing on the beach at
Jupiter, waiting for it to hit you? In practical terms,
I think the results
would be pretty much identical...

Sterling K. Webb
------------------------------------------------

Chris Peterson wrote:

> Are you sure about that? There is some question about the dynamics of the
> water displacement- that is, most of it goes up, not out. And that total
> volume of water is somewhere between a few tens and few hundreds of cubic
> kilometers. Contrast that with the recent Indian Ocean event. The shift in
> the ocean floor resulted in the displacement of over 1000 cubic kilometers
> of water, and produced waves in most locations of 3-5 meters.
>
> While an asteroid impact seems like a dramatic thing, it is far from obvious
> to me that tsunamis larger than 10s of meters would be a natural result.
> Since simulations seem to show everything from a few meters to 100 meters or
> so, I think I'll just reserve judgment until those simulations settle down.
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
Received on Wed 12 Jan 2005 10:58:36 AM PST