[Rockhounds] New Madrid fault

[Alan Goldstein]

I've read reports regarding studies of prehistoric sandblows, where 
earthquake causes ground liquefaction and geysers of wet sand spewing from 
cracks in the earth. Geologists dig trenches through sediments looking for 
them. I think the evidence indicated a major quake (on the scale of the 1812 
events) recurring on average about every 500 years. Not everyone of them 
would create a Reelfoot Lake. That would depend on whether the fault block 
that shifted was located under the Mississippi (or Ohio) River.

With regards to the effects of glaciation, the southern-most tip of the 
continental glaciers (the Illinoisian?) reached into southern Illinois. At 
that point, the ice probably thinned to less than 100 feet and stopped 
advancing. Although 100 feet of ice is heavy, I can't see how it would be 
heavy enough to trigger an earthquake. The New Madrid fault zone is an 
unglaciated area. I've read studies that hypothesize that the weight of the 
Mississippi River sediments on the highly faulted basement rock are thought 
to keep the system active. Last time I checked, the Mississippi and Ohio 
Rivers are still sending sediment through the fault zone and down to the 
Gulf of Mexico.

Even if the New Madrid fault zone produced one 7.5 to 8.0 magnitude quake 
every 10,000 years, consider how many "big ones" occurred in the past 700 
million years! There is one fault block in Livingston Co., KY that has 
several thousand feet of vertical displacement!

Alan G.


----- Original Message ----- 
From: "Axel Emmermann" <axel.emmermann at pandora.be>
To: "'Rockhounds at drizzle.com: A mailing list for rock and gem collectors'" 
<rockhounds at lists.drizzle.com>
Sent: Sunday, March 22, 2009 7:54 AM
Subject: RE: [Rockhounds] New Madrid fault


>> I am thinking
>> statistics here - what are the odds of this happening in this millennium
>> (much less this century)?
>>
>> Alan G.
>
> [Axel] There's an unusual way to find out whether a fault is short-term
> dangerous or not... If it is, there is probably a name for it in the tales
> and myths of the local people. Think about Pompei... in 79 AD  it was
> destroyed by the eruption of Mount Vesuvius.  We know of that because of 
> the
> ruins and letters of Plinius the younger.  But what if we hadn't had 
> written
> testimony? We know that Krakatau is a cataclysmic and recurring volcanic
> explosion. There have been movies made about it, documentaries, books...
> still millions of people have chosen to live in the "death zone" after a 
> few
> years. Were it to blow up now there would be millions of casualties.
>
> Still, chances of surviving a large earthquake are better than those of
> surviving a large volcanic eruption... No lahars, pyroclastic flows, lava,
> pressure waves, climate changes, ash rains...
>
> If I were looking for an answer about the dangers of a seismic zone, I 
> would
> go looking in the mythology of the locals and first of all: the place 
> names
> in the local language If I'm not mistaking that would be in Sioux.
> Names like: land that dances; land that moves, land that glows (quake
> lights), shaking land, sand fountain ... Things like that.
> Reelfoot lake is a good example...
> http://visitreelfootlake.com/reelfootlegend.htm
> If cataclysmic earthquakes happen with intervals that span periods greater
> than collective memory they will not reflect on the place names. If they
> happen more regularly you 'll most likely find place names referring to 
> it.
> Writings can such legends alive for much longer than a few hundred 
> years...
> Think of Sodom and Gomorra. Those became myth centuries before the written
> word became a general tool for recording history. Still, we know of them 
> and
> archaeology seems to confirm their existence in the distant past.
>
> Axel
>
>
>>
>> ----- Original Message -----
>> From: "J Bryan Kramer" <codeburner at gmail.com>
>> To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors"
>> <rockhounds at lists.drizzle.com>
>> Sent: Saturday, March 21, 2009 11:53 AM
>> Subject: [Rockhounds] New Madrid fault
>>
>>
>> I thought some may be interested in this:
>>
>> <http://www.sciencedaily.com/releases/2009/03/090313145956.htm>
>>
>> Do deep subsurface faults always produce measurable surface movement?
>>
>> BK
>>
>> --
>> "It often seems to me that the night is much more alive and richly 
>> colored
>> than the day."
>>
>>                       Vincent van Gogh
>>
>> J Bryan Krämer       North Florida, USA
>> photos at: http://pbase.com/photoburner
>> blog at: http://www.photoburner.net
>>
>>
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