Hi,
You missed the key sentence in the description:
"The impact structure is completely buried under
1000 to 1600 feet of sediment," meaning it's buried
under the sea floor of the Chesapeake Bay. The
features were located with drilling and mapped
with reflection studies. The Tom's River Canyon
crater is also under the sea.
It's likely the sea was very shallow when it was
formed. It's very hard to determine when and how
much of the continental shelves are underwater at
any given time. Just 18,000 years ago, they were all
exposed, and the sea level was up to 400 feet lower
than now. The slope of the shelves is gentle, and
small rises and falls cover (and uncover) a lot of
territory.
One lesson of this is how easy it is to hide a
humping big crater on an active planet like ours.
don't want to pay the $32 to download it...
For free:
Here's a short summary from C. Wylie Poag:
http://www.lpi.usra.edu/meetings/lpsc97/pdf/1029.PDF
And an abstract:
http://geology.geoscienceworld.org/cgi/content/abstract/30/11/995
Here's a complete paper:
http://www3.imperial.ac.uk/pls/portallive/docs/1/3773904.PDF
Big chunks of the ejecta landed 300 miles away,
in New Jersey. People are always dumping stuff in
New Jersey...
http://www.oceanleadership.org/files/USSSP/PDFs/Greatest_Hits/Events/McHugh.pdf
The secondary craters are detailed here:
http://www.lpi.usra.edu/meetings/LPSC99/pdf/1047.pdf
Here's the stratigraphy, blah, blah...
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1019.pdf
Here's a 61-page book on the effects of the crater.
Might as well download it for free -- your tax money
paid for it!
http://pubs.usgs.gov/pp/p1622/p1622.pdf
Here's another book, an 85-pager, that you paid for...
http://pubs.usgs.gov/of/2004/1016/2004-1016.pdf
with lots and lots and lots of articles!
Go crazy, EMan.
Sterling K. Webb
-----------------------------------------------------------------------------
----- Original Message -----
From: "Mr EMan" <[email protected]>
To: "metlist" <[email protected]>
Sent: Wednesday, July 29, 2009 1:36 AM
Subject: Re: [meteorite-list] Chesapeake Impact Specifics?
Ok Ok ok... I found this article cited (but don't want to pay the $32
to download it):
"Ancient impact structures on modern continental shelves: The
Chesapeake Bay, Montagnais, and Toms Canyon craters, Atlantic margin
of North America by C. Wylie Poag, Jeffrey B. Plesciab and Phillip C.
Molzera" in "Deep Sea Research Part II: Topical Studies in
Oceanography
Volume 49, Issue 6, 2002, Pages 1081-1102
Ocean Impacts: Mechanisms and Environmental Perturbations " and it
cites 23 additional craters associated with Chesapeake Not including
Tom's( River) Canyon. I assume these are all subsurface. Anyone with
access to the article, does it have a graphic/map for this crater
field or explain how they were located?
Looking at the cross section at Wikipedia; the breccia "pile" is 99%
contained in the buried crater so it may be 4200ft thick and the
central peak is far below the rim of the crater so it may be 3000ft
high. What the author failed to mention is that the whole structure
is more than a half mile below ground level!
I guess all things are relative but we fail to grasp the relationships
at times--in this case to "sea level". Speaking of sea level which we
know varies over time-- the new testament speaks of the "Sermon on the
Mount". Well been there and done that and the "Mount" is about the
size of a buried school bus--AND it is about 400 ft below sea
level--another thing not depicted correctly in 2000 years of bible
inspired art.
Elton
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