[meteorite-list] Scientific Value of Carancas Crater Research

[Sterling K. Webb]

Hi, Bernd, List,

    You are right about the "terraced" look of the
Carancas crater! It seems to show best in the earliest
photos; I suspect some dirt from the rim has cascaded 
down the walls in the intervening days.

    True "terracing" only occurs in large impact craters. 
After formation, the walls of the crater become unstable
(because they're so steep), and gravity causes them to 
collapse. These landslides create a "blocky" appearance, 
forming steps down to the crater floor. It's more common 
in large older craters.

    I believe the "terraced" appearance of the walls of
the Carancas crater is due to the rocky strata in the soil
being broken by the explosive excavation of the crater. 
The "terraces" seem to "step back" at the 30 degree angle 
of the crater walls.

    The INGEMMET summary characterizes the geology
of the region as Cenozoic limestone and mentions relatively 
weak stones: "sedimentary rocks (molasses or red beds: 
siltstones, shales and slates)"

    There appear to be some "blocky" stones in the pictures
of the fresh ejecta blanket. Mike Farmer talked about "blocks" 
of hard dirt landing on rooves. It's possible the two are the 
same (weak stone, hard dirt).

    Mike thinks there's a one-ton stone in the crater and the 
Canadian scientist Peter Brown is talking about "a ten-ton 
monster," while I really doubt that there's anything much 
to be found in the crater. I've been told by someone who
was there that the Carancas stones are extremely weak, that 
by "pressing two together in one hand, you can crush [them] 
to dust." 

    That does not sound like material that would survive any
substantial impact force. Whether the event was equivalent to 
1 ton of TNT, 5 tons (seismic reading), or 15-20 tons (as 
Peter Brown suggests) doesn't matter if they're that weak.

    Yes, this IS a crater worthy of study. And with every 
passing day, that seems less and less likely to happen.


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message ----- 
From: <bernd.pauli at paulinet.de>
To: <meteorite-list at meteoritecentral.com>
Sent: Tuesday, October 16, 2007 1:56 PM
Subject: [meteorite-list] Scientific Value of Carancas Crater Research


Hello List,

After repeatedly scrutinizing the available crater pictures of the
Carancas crater and trying to find out what is so exciting about
it, I've come to the conclusion that it looks pretty much like the
terraced walls of several lunar craters - for example: Tycho or
Copernicus.

While it would be (or: would have been) extremely important to
retrieve the main mass at the bottom of the crater as quickly as
possible, it may also be a serious mistake not to document, study
and examine each and every detail of this "crater-forming" event!


Carancassically,

Bernd

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