[meteorite-list] Volcano Bombs & Impact Breccia Identification
From: mark ferguson <refam_at_meteoritecentral.com>
Date: Thu Apr 22 10:23:55 2004
Hello Mark and List
Bombs are typically highly vessiculated magmas. What
you may be thinking of are ejected "old" magmas which
are ripped from the walls of a volcanic vent and would
have shapes that are irregular if not just plain
blocky. These differ from bombs in that they are from
previous events and may be breciated magmas, and that
becomes then a problem to determine origin other than
terrestrial. Bombs on the other hand, will usually be
of freshly melted material and can be very frothy in
texture as well as having aerodynamic forms. Both
types can occur in an eruption, but I'd expect ash to
be the more common found with old magma ejecta.
--- Mark Fox <unclefireballmtf_at_yahoo.com> wrote:
> March 31, 2003
> Greetings Meteorite Enthusiasts!
> I may not have found an actual space rock yet, but I
> have strong suspicions that I did when it deals with
> impact crater material. Keep in mind these are rock
> pieces found in end moraines deposited by glaciers,
> since there is no bedrock near my location as far as
> I know.
> This is where I need to ask the questions:
> 1. Are volcano bombs commonly found in Michigan and
> are they ever mistaken for impact breccias?
> 2. Also, are there any good clues that distinguish
> terrestrial breccias from the impact created ones?
> Thank you again for everyone's help! I hope you all
> are continuing to keep finding those black "Park
> Forest" rocks! It just so happens that one of the
> pictures I saw of one reminds me of the black melt
> veins seen in the Rose City H5 chondrite.
> Best regards,
> Mark Fox
> Newaygo, MI USA
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Received on Mon 31 Mar 2003 04:25:49 PM PST