[Rockhounds] glacial erratics (was Stonehenge geology resolved)

[pmodreski at aol.com]

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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