[meteorite-list] Peru Again!! Ubinas, Peru volcanic bomb block crater- Smithsonian Institution-INGEMMETstudy

[Sterling K. Webb]

Hi, Dirk, List,

    The picture of the 2-meter "bomb" shows there
no distinction between an impact pit (which is what
this is) and a true crater, formed by an explosion.
The shape (but not the size) is the same for both.
The object's mass is up to 10 tons, but the velocity
was low, probably no more than 100 m/sec (depends
on how high it was tossed out of the volacano). A
"pit" is a low-energy event; a crater is not, but the
shape's the same.

    The geometry of the pit or crater is very close
to that perfect conical shape of the mathematical
crater models with their 3:1 width-to-depth. But since
it's the energy that determines the crater, you could
have gotten the same crater that was produced by
ten tons at 100 m/sec with 100 kilos at 1000 m/sec,
or 1 kilo at 10,000 m/sec.

    It's a picture like this that demonstrates the true
silliness of the idea that a "ten-ton monster" is hiding
in the Carancas crater. The URL's a picture of a
ten-meter crater (OK, pit) with a ten ton impactor
sitting in it. Does it look to you like it's hiding? I think
we'd have noticed a ten-monster in Carancas... if it
was intact!


Sterling K. Webb
---------------------------------------------------------
----- Original Message ----- 
From: "drtanuki" <drtanuki at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Tuesday, October 16, 2007 8:01 PM
Subject: [meteorite-list] Peru Again!! Ubinas,Peru volcanic bomb block 
crater- Smithsonian Institution-INGEMMETstudy


Hi List,
  Thought some of you might be interested in seeing
another crater in Peru.  Take a look at the photo page
at least!  Best Regards, Dirk Ross...Tokyo


Main Page:
http://www.volcano.si.edu/reports/bulletin/contents.cfm?issue=3110&display=complete


Photo:

http://www.volcano.si.edu/volcanoes/region15/peru/ubinas/3110ubi7.jpg

Figure 14. Ubinas eruptions in May 2006 ejected
volcanic bombs, seen here in their impact craters. A
2-m-diameter bomb (top), struck ~ 200 m from the
crater. A crater containing a large, partly buried,
smooth-faced bomb is seen in the bottom photo.
Numerous bucket-sized angular blocks appear on the far
side of the impact crater. Two geologists stand
adjacent a ~ 2-m-long block that ended up on the
impact crater's rim. The bomb fragments were of
andesitic composition. Top photo from Salazar and
others (2006); bottom photo from INGEMMET website.
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