Meteorite Impact Evidence near Gunflint Lake

From: "Mark Jirsa" <jirsa001@umn.edu>
To: <gta@boreal.org>
Sent: Tue, 28 Oct 2008 09:55:34 -0500
Subject: Meteorite



I'm writing to tell you about some web content that might interest your
resort clients and their guests. During the Ham Lake Fire in 2007, I
discovered some unusual rock layers near Gunflint Lake that hold evidence of
one of the worlds largest and oldest meteorite impact events. Although the
deposits were first identified in Thunder Bay in 2005, this is the first
discovery in rock outcrops in Minnesota. The meteorite hit near Sudbury
Ontario 1,850 million years ago, and spread ash and debris, probably around
the globe. The impact was likely a "globe-killer," though there wasn't much
organic life to kill during that early time of Earth history. The
meteorite was so large and was moving at such a tremendous velocity that it
vaporized on impact, so no actual meteorite pieces exist near the Gunflint
Trail, or anywhere else.

Visit the Minnesota Geological Survey website ( <http://www.geo.umn.edu/mgs>
http://www.geo.umn.edu/mgs) and click on the left menu "NEW--Minnesota's
evidence of an Ancient Meteorite Impact"

A slightly expanded version, also for the lay audience, appears in the
December 2008 edition of ASTRONOMY MAGAZINE

If you or any of the resort operators and guests have questions, feel free
to contact me. I am happy to share information about where the rock
exposures are, what they look like, and how they formed. Scientific study
of these outcrops and others in the Lake Superior region is on-going.
Because they are in the Superior National Forest, and for the sake of
preserving scientific value, I discourage collection of rock
samples---photos say 1000 words though!

Mark