[Rockhounds] glacial erratics (was Stonehenge geology resolved)

Tue Feb 3 16:41:33 PST 2009

That glacier sure must have broken quickly.

Yours,
Dora Smith
Austin, TX
tiggernut24 at yahoo.com
----- Original Message ----- 
From: "Jeffrey T. Cessna" <jcessna at nist.gov>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" 
<rockhounds at lists.drizzle.com>
Sent: Tuesday, February 03, 2009 2:07 PM
Subject: Re: [Rockhounds] glacial erratics (was Stonehenge geology resolved)

> Take a look at this picture...
>
> http://static.panoramio.com/photos/original/234063.jpg
>
> subtract the lichen covering from the left half which slants back 
> (providing a growing surface)
>
> Subtract the iron staining from the right half which leans forward 
> (causing it to drain between the layers)
>
> maybe?
>
> Jeff
>
>
>
> At 02:27 PM 2/3/2009, you wrote:
>>I don't doubt your proposed possiblity Pete, just thinking numbers --
>>I haven't seen a whole lot of rocks broken and sagging in the middle.
>>Just threw that in as more ammunition as I expressed my pondering if
>>it is a rock broken in two where it rests or several rocks that just
>>happened to end up at the same spot. I can't imagine any reason why it
>>couldn't be two separate rocks from the same "avalanche fall on to the
>>ice" or otherwise plucked from the bedrock.
>>
>>Out of curiosity, I searched the web and looked at a lot of photos,
>>none of which really helped. The Okotoks Erratic is quite a pile of
>>rocks, hiding behind those two big pieces, with three main pieces and
>>a lot of little ones. None of the photos were useful for lining up the
>>layers to see if the two sides even matched in layers. As to the one
>>side of those two largest pieces looking much more broken up and more
>>rusty than the left piece, in some photos, they didn't look all that
>>different.
>>
>>Nothing like computer-side geologizing.
>>
>>Regards,
>>
>>Lanny
>>
>>
>>
>>On Feb 2, 2009, at 9:52 AM, pmodreski at aol.com wrote:
>>
>>>Well, heck, Lanny, the explanation is all right there in the story
>>>link that Kreigh sent, how the rock was split by the bats as they
>>>were trying to save Napi, the supernatural trickster of the Blackfoot.
>>>
>>>Trying for the more scientific interpretations, perhaps, if the rock
>>>had been carried to this spot as one more or less intact block by
>>>the glacier, it could have been resting on stagnant glacial ice
>>>after the ice sheet stopped moving, and melting away of support
>>>underneath it might have undermined the rock and caused it break
>>>apart if it couldn't support its own weight; or, it might even have
>>>toppled off an ice cliff at the terminus of the glacier, perhaps
>>>while the ice was still flowing.? Or, being weak in its center,
>>>perhaps it was broken into several pieces while it was still being
>>>carried along.
>>>
>>>lots of possibilities?
>>>
>>>
>>>-----Original Message-----
>>>From: Lanny R <lanny.r at roadrunner.com>
>>>To: Rockhounds at drizzle.com: A mailing list for rock and gem
>>>collectors <rockhounds at lists.drizzle.com>
>>>Sent: Mon, 2 Feb 2009 10:13 am
>>>Subject: Re: [Rockhounds] glacial erratics (was Stonehenge geology
>>>resolved)
>>>
>>>
>>>I have a doubt about the "Big Rock," this Okotoks Erratic really
>>>being one rock broken into two pieces. First, I don't recall ever
>>>seeing a large rock that I was sure had obviously broken into two
>>>pieces where it had settled in the middle so that the two pieces
>>>dipped inwards. Secondly, I can't see any match in the layers
>>>between the two pieces. That might be just a problem of how it is
>>>shown in the photograph, so that one can't really see them all that
>>>well. Thirdly, the piece on the right is more broken up and has a
>>>lot of rusty layers, very unlike the left piece.?
>>>?
>>>Any others care to express their opinion on this??
>>>?
>>>Regards,?
>>>?
>>>Lanny?
>>>?
>>>On Feb 2, 2009, at 8:48 AM, pmodreski at aol.com wrote:?
>>>?
>>>>Neat website about that big rock, Kreigh!?
>>>>?
>>>>?
>>>>Some erratics are big. You might enjoy the size of the biggest one??
>>>>??
>>>>http://culture.alberta.ca/museums/historicsiteslisting/okotokserratic/default.aspx? 
>>>>?
>>>>??
>>>>and the interesting legend of how it split in two.??
>>>>??
>>>>Kreigh??
>>>>?
>>>>?
>>>>And, alas, I'm afraid your post was a great disillusionment to me,
>>>> > because I couple of years ago I had visited, and was very
>>>>impressed > by, the Madison, Carroll County, New Hampshire, glacial
>>>>erratic, a > N.H. State "Wayside Monument" and locally known as
>>>>"the largest > known glacial erratic".? It is,?
>>>>?
>>>>?
>>>>"Madison Boulder is a huge granite rock measuring 83 feet (25 m) in
>>>> > length, 23 feet (7.0 m) in height above the ground, and 37 feet
>>>>(11 > m) in width. It weighs upwards of 5,000 tons."?
>>>>?
>>>>Your Okotoks Erratic "Big Rock" in Alberta has?clearly got it all >
>>>>beat,?
>>>>?
>>>>"The Okotoks Erratic weighs 16,500 tons. It measures 9 metres high,
>>>> > 41 metres long and 18 metres wide."?
>>>>?
>>>>and?evidently holds the world record, as is stated in the very good
>>>> > Wikipedia article about glacial erratics,?
>>>>?
>>>>http://en.wikipedia.org/wiki/Glacial_erratic?
>>>>?
>>>>Next time I'm in Alberta (never been there, actually), I've got to
>>>> > see it!?
>>>>?
>>>>Cheers, Pete?
>>>>?
>>>>?
>>>>?
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