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.
also, try this:
Regards,
Jason
On 5/3/06, Sterling K. Webb <[EMAIL PROTECTED]
> 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" < [EMAIL PROTECTED] >
To: "Meteorite-list" <[email protected] >
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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