Re: Flood Deposits in Mesopotamia [Was: Special Creation]

>>>>From Glenn: GRM: Now, do me a favor. You asked for quantitative data. I
provided it in the form of a calculation of how much flood water was required
to deposit your 1 mm of sediment (the thin veneer flood). I calculate that
about 3 inches of water is all that is required at a 3% by weight sediment load.
But, in your response, you don't respond to that point. I must confess to
being a bit disappointed. In order to have a flood which leaves 1 mm of sediment
(something I would have to agree would be hard to find), you have to have a
flood which is little more than distilled water--no sediment load, no dissolved
matter. THat is unlike any flood I have every seen or heard of. Can you point
me to one single example in earth history?<<<<
From Phil:

Glenn, I thought I did respond. My first statement was that I really can't
go anywhere with this until I get an actual, quantitative description of the
basin and then do some numerical modeling of possible flood scenarios. All we
are doing is throwing around rules of thumb. It is a rule of thumb that you
stated, that floods often carry 3% sediment load by weight. A rule of thumb
isn't going to settle the argument because that 3% doesn't get distributed
homogeneously. You also quoted the Mississippi flood with 10 feet of sediment.
That wasn't 10 feet over the entire flooded region! That flood, too, laid down
the sediments non-homogeneously. If it put 10 feet in one area, then it must
have put a lot less in many other areas.

Where does a mesopotamian flood leave its 3%? Does it leave it all in
northern mesopotamia? If so, then southern mesopotamia will get **no** sediment,
because the waters will have lost their load before they do south. Do they
leave it in southern mesopotamia? Then they leave none in the north, because they
had to keep it to take it to the south. Let's say that the 3% sediment load
is deposited uniformly all down the basin from top to bottom, so that by the
time you reach the gulf it just gets to 0% load left over. That comes out to
about 5 nanometers of sediment spread equally across the entire basin.

But you will reply that the rivers pick up new sediment all along the way.
But if that is true then you get no net sediment added to most of the region.
To state the idea more precisely, if you assume a constant 3% sediment load
all the way down the basin, then the net deposition of sediment must precisely
equal the net entrainment of sediment everywhere. Its just conservation of
mass. No net change in load means that total deposition must equal total
entrainment. Therefore, there will be no net change in the amount of sediments all
along the way. They will just have been moved around.
But the reply to this might be that the water (especially wind-generated
wavers) will scour up silt out from the native sands, segregating the silt and
carrying them away to deposit on top of the sands. Therefore, native silt (not
just silt from the mountains) will contribute to the deposits and it will be
seen as silt, not sand, when it is deposited. True. But aeolian sand contains
very little silt. I have about 100 bottles of sand sitting over my computer
monitor, and I just finished examing the 5 or 6 different sands that I have
from Tunisia, and there are zero visible silt-sized particle in them. (I don't
have any sands from Iraq, unfortunately.) This lack of silt in the Tunisian
sand is because aeolian sands have been worked by the wind for so long that they
eventually obtain a log-normal size distribution peaked at rather large
particle sizes. Sooner or later the silt all ends up in the water somewhere and
then sinks to the bottom never to return, or else it is held down by vegetation
as part of true soil (which is not the same as aeolian sands). Iraq does have
lots of dust, which is dry silt, but that is typically a tiny surface
fraction of what lies under the dust, because the sand sinks beneath it. I may be
wrong, but that's what my study of aeolian sand has taught me.

But let's say that geologists can identify even sand when it gets redeposited
by a flood. Oh really? After 5000 or more years of the wind blowing on it,
with no vegetation or cities beneath it, it won't get thoroughly mixed with
all the other migrating dune sand? I don't know, but it doesn't seem
reasonable. You can identify 10 feet of mississippi sand because it wasn't there
before, or because it is on top of houses or grass. But aeolian sand moved by water
and left on aeolian sand doesn't look like anything special at all,
especially after 5000 of activity.

Another answer might be that new sediment is constantly coming in from the
mountains around the basin and so the 5 nanometers deposit per 3 inches of water
coming into the valley gets multiplied by many, many fresh incoming inches.
That is true. But here is precisely why I can't give you an answer. I can't
tell you how much water had to come in from the mountains. If the flood was
of short duration, and the then waters were simply held relatively stationary
over a long time by the shear force and wave generation of the wind, then how
much water was actually needed to come in from the mountains? It's not 1 year
of water flowing in; it's much less.

You and I agree that none of these things adequately answer you, nor do they
disprove you, nor do they prove anything at all. They are just more qualitive
statements and rules of thumb. And that's exactly why I said that I cannot
contribute any more to this discussion. Unless we get some honest-to-goodness
number crunching, I feel it is all just words, words, words.

I appreciate your honesty. I also appreciate your very important challenges
which need to be studied and analyzed. But we need peer review in both
directions. Qualitative arguments can't settle the argument in either direction.

Here is my bottom line: if the evidence doesn't support a big flood, then it
must have been a small one. If it doesn't support a northerly flood, then it
must have been a southerly one and we have to reinterpret RRT (which we have
thought meant Ararat, but with some dissent). It might come down to how rigid
are we in our understanding of the text. The culture that described to us
the resurrection is relatively modern compared to the culture that communicated
the flood. There is not much comparison between them. Personally, I don't
think we can be that rigid with understanding how the earlier culture described
things. It was written so long ago that we do not thoroughly understand it.
We don't even know what kind of number system they were using back then. We
don't know a lot of things. But we know that we are told there was a
signficant flood that killed everyone within Noah's sphere of influence, and he was a
man who loved God and was warned and hence became a picture of salvation.
Trying to make rigid interpretations out of it seems relatively unimportant to me.
 It's interesting and it may be helpful apologetically, but I can live with
the uncertainty about how we read the text. I believe we need lots of
flexibility to account for cultural differences and that solves it.

God's blessings to you!

Phil
Received on Fri, 10 Mar 2006 18:05:12 EST