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Author Topic:   Exploring the Grand Canyon, from the bottom up.
jar
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Posts: 30981
From: Texas!!
Joined: 04-20-2004
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Message 1 of 282 (294871)
03-13-2006 10:53 AM


I'd like for us to discuss the Grand Canyon, beginning with the lowest, oldest layers and then working up to the top, layer by layer. I'd like to see explanations for each layer, it's composition, the environment when it was created, and get questions about that layer answered before we move up to the next layer.

If possible, can we begin with the Vishnu Schist?


Replies to this message:
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 4 of 282 (294904)
03-13-2006 11:38 AM
Reply to: Message 3 by Gary
03-13-2006 11:33 AM


Re: Wikipedia article
Yes and other sources as well. But here I'd like to concentrate of an orderly and leisurely exploration from the bottom up.

Right now all I want to discuss is the Vishnu Schist.


Aslan is not a Tame Lion
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Replies to this message:
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 5 of 282 (294956)
03-13-2006 4:02 PM


Bump for roxrkool
Can you help here?


Aslan is not a Tame Lion
Replies to this message:
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 7 of 282 (294969)
03-13-2006 4:59 PM
Reply to: Message 6 by roxrkool
03-13-2006 4:26 PM


Re: Vishnu Schist
A couple questions if I might.

One of the things you mentioned was mica. I remember as a child exploring some of the mountains in western Maryland. There I sometimes found mica. It always fascinated me since it's unlike almost any other rock I'd find (except maybe asbestos). It was almost clear and would separate into very flat thin sheets.

Can you tell me a little about Mica and how it is formed?

Conglomerates are conspicuously absent in the Vishnu metasedimentary rocks

That's nice. But what does that mean?


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 9 of 282 (295160)
03-14-2006 10:00 AM
Reply to: Message 8 by roxrkool
03-13-2006 5:08 PM


a couple questions you might have missed.
I think I was posting this question while you were replying above. Can you look at Message 7 and see if you can help me?


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 13 of 282 (295287)
03-14-2006 3:52 PM
Reply to: Message 12 by 8upwidit2
03-14-2006 3:46 PM


Re: Grand Canyon Layers Billions of years old
Well, we'll likely find the answer to that question as we go on. Right now though all we are dealing with is the Vishnu Schist layer.


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 15 of 282 (295299)
03-14-2006 4:24 PM
Reply to: Message 14 by PaulK
03-14-2006 3:54 PM


Re: Grand Canyon Layers Billions of years old
Paul, thanks for the post and I hope you'll continue to contribute, but I really want to keep this one very narrow and organized so that it doesn't get pulled off into the "Big Picture". Can you help by sticking to the Vishnu Schist until we move on to the next layer?


Aslan is not a Tame Lion
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jar
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Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 17 of 282 (295342)
03-14-2006 7:30 PM
Reply to: Message 16 by Minnemooseus
03-14-2006 4:58 PM


Re: Vishnu Schist - No conglomerate in the protoliths
Okay, but still a few questions.

You say:

Metasedimentary rock = Metamorphic rock that was formed from the metamorphism of sedimentary rock.

Metamorphic rock. Does that mean that the form of the rock has changed?

What I get from all this is:

The Vishnu Schist began life as a sandstone, but was changed to what you guys call schist over time by temperature and pressure. That schist is a coarse grained rock and since it is formed at a higher temperature and pressure than say, slate, it is also harder.

Is that correct?


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 20 of 282 (295354)
03-14-2006 8:35 PM
Reply to: Message 19 by roxrkool
03-14-2006 8:26 PM


Re: Vishnu Schist - No conglomerate in the protoliths
Okay, sticking to the Vishnu Schist.

It began life as sandstone. In the post to Moose you hint at the origin of the sandstone, but for now I'd like to put that off beyond simply saying that the Vishnu Schist was once a mountain that got eroded down into sandstone that later got buried and under pressure turned into schist.

Is that correct so far?


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 22 of 282 (295362)
03-14-2006 9:30 PM
Reply to: Message 21 by roxrkool
03-14-2006 9:24 PM


Re: Vishnu Schist - No conglomerate in the protoliths
Okay, but that seems to be talking about the Grand Canyon supergroup and I'm not sure we are there yet. The Vishnu Schist is below the Super Group IIRC. We'll get to it soon.


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 24 of 282 (295368)
03-14-2006 10:04 PM
Reply to: Message 23 by roxrkool
03-14-2006 9:47 PM


Moving on to the Zoroaster granite
I think I have it now.

So from the bottom so far we have one level that started out as sandstone but later was transformed into schist. The sandstone was a second generation product that had been produced by wearing down some earlier formation.

If that's okay, I'd like to move on to the question about Zoroaster granite.

The Zoroaster granite is both below and within the Vishnu schist.

Let me ask three questions to start this off.

First, what is the difference between schist and granite?

How did the Zoroaster granite get below and within the Vishnu schist?

Is the Zoroaster granite then younger than teh Vishnu schist?

edited to fix subtitle

This message has been edited by jar, 03-14-2006 09:09 PM


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 43 of 282 (295498)
03-15-2006 10:45 AM


Can we head back towards the topic.
I would like for us to move back towards the topic. To do so I would like to make a summary of where we are.

I think I have it now.

So from the bottom so far we have one level that started out as sandstone but later was transformed into schist. The sandstone was a second generation product that had been produced by wearing down some earlier formation.

If that's okay, I'd like to move on to the question about Zoroaster granite.

The Zoroaster granite is both below and within the Vishnu schist.

Let me ask three questions to start this off.

First, what is the difference between schist and granite?

How did the Zoroaster granite get below and within the Vishnu schist?

Is the Zoroaster granite then younger than the Vishnu schist?

Then it was said that Granite is an igneous rock and was an intrusion into the sandstone layer that became the Vishnu Schist.

So at this point we have solid evidence of at least four events.

There was some rock forming event at some time in the past.

That rock was worn down into sand.

The sand was transformed in sandstone and then later into the Vishnu Schist.

During the process there was a tectonic event and Zoroaster Granite intruded into the Vishnu Schist.

Now there is no speculation in this summary so far that I can see.


Aslan is not a Tame Lion
Replies to this message:
 Message 45 by Jazzns, posted 03-15-2006 11:44 AM jar has responded

  
jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 44 of 282 (295503)
03-15-2006 10:52 AM
Reply to: Message 42 by Faith
03-15-2006 10:40 AM


Re: Dating
Don't worry. I will try very hard to keep this on topic and to make sure that there is no speculation. There is no need for either speculation or dates to prove that the Grand Canyon is old and that there was no Flood.

I will work as hard as I can to keep this focused on the facts. Just be patient. We have only touched on two of the many, many layers of the Grand Canyon and only four specific events so far.

A date in geological time cannot be a FACT, I don't care HOW much evidence supposedly supports it.

Well, don't worry. We will try to simply present the facts and let the readers make their own judgements about the dates.


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 46 of 282 (295524)
03-15-2006 11:52 AM
Reply to: Message 45 by Jazzns
03-15-2006 11:44 AM


Calling for geologist input on aisle 11
So before we move on, we need an answer to two more questions.

Is the Vishnu Schist an example of contact metamorphos or compression metamorphos and how can the difference be told?


Aslan is not a Tame Lion
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jar
Member
Posts: 30981
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.7


Message 49 of 282 (295546)
03-15-2006 12:43 PM
Reply to: Message 47 by IrishRockhound
03-15-2006 12:27 PM


on the ordering
Okay. From this I gather that it's possible to have metamorphic rocks that were formed by two different processes, and to determine which process was involved we'd need to look at an idividual sample.

Overall though, it's possible to assert a general order, that goes like this so far.

Rock is created.

Rock is eroded into sandstone.

Magma intrudes and becomes granite.

Sandstone is put under heat (the heat could come from the magma or just the pressure of being buried under other levels or a combination of both) and becomes schist.

Is that a reasonable summary of what is found in the Vishnu Schist and Zoroaster Granite levels.


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