[meteorite-list] Re: possible impact crater -- Nicaragua, Chad, Algeria

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu May 4 12:07:24 2006
Message-ID: <004401c66f1b$f4a34a20$5f2f4842_at_ATARIENGINE>

Hi, Stefan, List

    I think you got a crater there! The most impressive view
is to set your altitude around 30 or 40 miles up, orient yourself
to the NE of the crater, looking to the SW, then tilt the view
until your eye level is at about 4 miles up, and zoom in slightly.
Wow! That is a classic crater. That view alone is convincing...
almost. It needs to be seriously investigated.

    Google Earth's view can be deceptive. I always trace the
"rim" and "cavity" of what appears to be a crater and read off
the altitudes to see it actually has a crater's geometric shape.
Parts of the Nicaraguan crater's rim are half a kilometer or
more above the floor.

    Jason Utas' candidate in Chad is an example of the
deceptiveness of visual features. Knowing the shape of a
crater, we interpret the dark areas in the "floor" of what
looks like a crater as depressed and the bright features
as central uplift and rim, but the dark features are actually
as high or higher than the bright ones. When you tilt the view
you see that the whole feature is elevated, like a squashed
mountain. Oddly, it seems to be set in a square embayment.
Very strange. It doesn't look entirely volcanic but it doesn't
look much like a crater, either.

Kevin Forbes' Algerian feature is essentially flat and consists
of concentric rings of contrasting materials. Its appearance
reminds me a lot of the much larger Richat Dome in Mauritania,
whose crater or not status has been argued over for a long time.
Currently, we don't think the Richat is a crater, but a domed,
layered structure sliced off flat to reveal its layers. His "less
probable" structure looks more like a crater in the tilted view,
but it is too battered to tell much. The Sahara is not kind,
even to rocks...


Sterling K. Webb
-------------------------------------------------------------------------------
----- Original Message -----
From: "Stefan Brandes" <brandes_at_gmx.at>
To: "Meteorite-list" <Meteorite-list_at_meteoritecentral.com>
Sent: Sunday, April 30, 2006 1:21 PM
Subject: [meteorite-list] meteorite-list] possible impact crater


> Hi list,
>
> has anybody heard about an impact crater in Nicaragua at coordinates :
> 13?21' N / 85? 57' W
> It?s about 12km in diameter and the town of Las Praderas lies directly in
> the center.
> It?s very good to see in Google Earth.
> As far as I know it?s definitely no volcano.
>
> Any ideas?
>
> Thanks
> Stefan
>
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Received on Wed 03 May 2006 09:42:07 PM PDT