[Rockhounds] glacial erratics (was Stonehenge geology resolved)

Tue Feb 3 11:27:25 PST 2009

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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