Re: New archaeological evidence casts doubt on mega-tsunami theory of Minoan collapse

From: Eric Stevens (eric.stevens_at_sum.co.nz)
Date: 01/09/05 

Date: Sun, 09 Jan 2005 13:00:51 +1300

On Sat, 08 Jan 2005 15:14:21 GMT, Philip Deitiker
<Donevenask@worlnet.att.net> wrote:

>Martyn Harrison <nospam@spammers.of.the.world.unite> says in
>news:blhvt011g4vrda7cd0po390k3mgmgg4758@4ax.com:
>
>> Apparently on date 7 Jan 2005 10:39:46 -0800, "grapheus"
>> <grapheus@www.com> said:
>>
>>>Dylan Sung wrote:
>>>> "grapheus" <grapheus@www.com> wrote in message
>>>
>>>Of course, the falling down into the sea of a piece of ice is
>>>similar to the falling down of a piece of rock.
>>>With a DIFFERENCE that you omitted to mention : As the DENSITY
>>>of ice is LESS than 1, contrarily to the density of a rock, the
>>>tsunami is generally NEGLIGIBLE. Because of what I said at the
>>>beginning (YES, we are going back to square one, to the point
>>>you didn't understand !!!) : What COUNTS is the "VOLUME of the
>>>WATER which is suddently DISPLACED...
>>
>> There is a fundamental flaw in your reasoning, which concerns
>> basic physics.
>>
>> Displacement of water is key here, this is true. How much water
>> is displaced when you abruptly submerge:
>>
>> 1) 100 cubic meters of ice with a density of 0.99
>>
>> 2) 100 cubic meters of rock with a density of 4.00
>>
>> ?
>>
>> *Hint*, 100 cubic meters of rock does not displace 400 cubic
>> meters of water.
>
>E = 1/2mv^2 E=mgh.
>
>If you take ice and drop it from 100 feet into water, it will hit the
>water with E and the ferrous-rock with 4E. The ice will create a
>displace wave of depth X where as the ferrous-rock rock will continue
>to displace water to a depth of 4X until its speed equilibrates with
>water. While ice is slowing the speed of the displacement wave is
>slowing , whereas the ferrour-rock continues to displace water at a
>faster pace. Once both equilibrate in speed the water will cover them
>and they will continue not to displace.
>
>In the example above g is constant, h is 100 feet for both, and mass
>varies by 4. The energy of impact is converted to heat which is
>quickly dissipated and motion, E = 1/2mv^2. Let us argue that argue
>that the rock falls into a sea of 100 feet, at its speed equilibrates
>at 90 feet, the ice equilibrates at 45 feet. The average speed of the
>rock over the 90 feet is 1/2 the contact velocity at 45 feet and the
>speed of ice is negligible. That initial speed is 24 m/s, the surface
>wave to 20 feet will be approximately half. The surface wave created
>by the ferrous rock will be about 3/4ths the subsurface displacenment
>of the ice will be negligable, the subsurface wave created by the
>falling ore will be about 1/4th that the surface wave.
>
> The essential flaw of your argument is that you fail to consider
>that E=mgh is the same E as 1/2mv^2. That kinetic energy is imparted
>on the adjacent body of water as it penetrates the water compressing
>and raising the water as it penetrates. The objects can be flat, and
>both with impart their energy at the surface, or fusiform and both
>pentrating and departing energy deep. But the ferrous object of the
>same shape as the ice will _Always_ depart its energy deeper than the
>ice. Because it imparts its energy deeper it carries the ability to
>move and copress water deeper. One the surface that displacement in
>created in the form of a verticle displacement. But under the surface
>a compression wave is created. Since water does not compress well
>that wave propogates very rapidly forward.
>
> What is important here to keep in mind is that when ice falls it
>generally creates only a surface displacement wave. Surface
>displacement waves travel in verticle displacement of rather slow
>speeds and in shallow water they frequently curl away their energy.
>A dense object can create a displacement wave, which can travel
>globally.
>
> Having said that I cannot think of a single example where a chunk of
>rock falling has created a tsunami.

See http://www.usc.edu/dept/tsunamis/alaska/1958/webpages/

>If one thinks about volcanic
>ejecta that ejecta falls back onto water at random points. For a
>really good tsunami one needs a very sharp line of change along the
>ocean floor. [Note I am not considering water impacts of a non-
>terrestrial origin]
> In terms of the Santorini event, my thoughts on the matter are
>this. It is not the surface displacement that would concern me. The
>submarine displacement of both water and solids would create a wave
>at the maximum depth of that ejecta. The exploding gas would
>immediately displace both water and debris before it redirected its
>energy on a path of least resistence. On the NW and WSW walls of the
>caldera this event is obvious, although we cannot say how exactly far
>in terms of water this occurred we can argue that the displacement
>moment was at least as far as the center of the caldera depression to
>the outside wall in terms of the distance traveled. Some of this was
>in the form of a surface wave, probably 100s of feet in height
>(meaningless at the point of generation since the ejecta is also
>blowing the wave off), but also on a submarine compression.
> Here is the base argument. If the rate of internal displacement is
>greater that the speed of tsunami propogation (500 MPH) then a
>tsunami is created. The Santorini caldera exploded from its center at
>a final velocity of greater than 500 MPH, and the WSW and NW borders
>protecting the ocean were destroyed clearly indicating this ejecta
>was thrust into the surrounding sea. The density of the horizontally
>moving eject is as important as falling rock.

Eric Stevens

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