Tsunami deposition

Allen Roy (allen@infomagic.com)
Sun, 25 Apr 1999 23:38:08 -0700

> From: Glenn R. Morton <grmorton@waymark.net>
> Are you aware that tsunami deposits are largely UNSORTED rubble with
> particles of all sizes?

"The uppermost sand sheet, which is within 11 cm of the marsh surface,
consists of massive, moderately well sorted, fine to medium sand. Twigs,
branches, logs, bark, seeds, and conifer cones and needles are scattered
through the sediment and also occur locally in a mat at the top of the sand

"An older sand sheet is widespread ... It consists of medium to very fine
sand and minor silt and is moderately well sorted. The sediment is
generally massive, although there are scattered granules and pebbles near
the base of the sand at some sites."

Clague and Bobrowsky, 1994, "Tsunami deposits beneath tidal marshes on
Vancouver Island, BC", GSA Bull, v.106, p. 1297

> > Since flooding mega-tsunami could only occure by impacts in large
bodies of
> > water, one would expect that the first depositions would contain
> > marine life.
> Why could astroids only hit the water? Did the land have asteroid
> blasting lasers that kept them at bay? Anti-asteroid cream?

One would expect astroids to also hit on the lands. But the ones landing
in the seas would be the ones to cause mega-tsunami to sweep ashore.

> besides, the large tsunamis, come on shore rapidly and bury LAND animals
> (and drag some of them out to sea). The land and marine animals should
> be mixed up in this model. Hundreds of New Guineans were sucked into
> the sea after their tsunami.

The highly turbulant front of a tsunami would not likely bury anything.
Deposition occures from the waters which follow the along behind the wave
front. Most of the large stuff would be kept in the wave front for some
time depending upon the energy of the wave. (Anyone who has wiped out
while surfing has experienced this first hand.) Occational erratics would
occure in the deposition following along behind the wave.

> As the mega-tsuanmi sweep inland (several waves would
> > generate from a single impact and each would follow the previous one
> > before the first had time to drain back off) more and more land would
> > innundated.
> So where are all the land animals that are on land when the first waves
> hit the beach. Your model should predicts a fossil order of 1. land
> animals 2. marine animals. This is backwards to what we see.

In the immediate area of the impact site the waters would become saturated
with rock and soils and animals and plants (typically marine). As the
waves radiate out, the leading wave fronts would strip away the original
surface. As the waters follow the wave fronts, the energy level drops and
the waters become supersaturated and deposition begins. The first to be
depositied will be what was origianlly in the waters. The wave fronts
would sweep the area clean and carry most of the debri on ahead. That
debri which could float would become mats following along behind the wave
fronts. As the wave begins to recede, tht mats could be left behind laying
on top the megatsunami deposition. Other tsunami could follow laying more
deposition on the first and even ontop of the debri mats depending upon the
energy level of the wave front as it reached the area.

So the first to be deposited would be marine sediments.

> > Just how this model can explain the deposition of forams, nannoplankton
> > diatoms as described, I don't know at this time. But, in my optimism
> > the model, I expect an explanation can be found.
> You are an unusually(unreasonably/blindly) optimistic fellow. You are
> suggesting that NO explanation is a reason to believe your view.

You are exceedingly pesamistic. I said that no explanation yet is not a
reason to abandon a model. There is a big difference.