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

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Fri May 5 11:12:36 2006
Message-ID: <93aaac890605041115q16152246i71e3c2576dc3fc9f_at_mail.gmail.com>

Hello Sterling, All,
I do realize that the 'craters' that I found were not, indeed, holes in the
ground. However, the 'craters' that I found, would not be depressions as
you described. Each consists of features well over ~15-20km across, the
diameter necessary to create a complex crater, and would therefore consist
of a central uplift with a series of concentric (raised) ridges.

In order to view mine correctly, try zooming out to forty miles or so and
having a look from up there. A much larger circular feature can be seen
about the central uplift of my favorite candidate. (Visible at 21 17'10.89"N
19 20'35.61"E ) This would be the area around the uplift that was shocked
and melted to some degree and also somewhat displaced.

The other consists of a large uplift and a single upraised ring about it,
making it appear very similar to the large impact feature recently
discovered near the Egypt-Libya border.

The features that you describe -- a hole in the ground with a raised rim
-- apply only to simple craters (which cannot, in most cases, at least here
on Earth, exceed the limit of approximately 15-20km in diameter). Stefan's
feature, measuring in at approximately nine miles across, appears to be a
rather large example (if it is actually a meteorite crater) of a simple
crater.

Here's an informative site that you might want to read, as it has some
rather good information on the subject.

http://www.lpi.usra.edu/publications/slidesets/impacts.html

also, try this:

http://www.solarviews.com/eng/tercrate.htm

Regards,
Jason


On 5/3/06, Sterling K. Webb <sterling_k_webb_at_sbcglobal.net > wrote:
>
> 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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>
>
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