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Author | Topic: A series of Questions for our Geologists. | |||||||||||||||||||||||||||||
jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Perhaps the worst thing to have ever happened to the field of Geology has been the advent of Google Earth. With Google Earth and all of the great photos that have been released since the cold war ended, idiots like me have been able to look down on the earth and pester you good folk to explain the wonderous things we see.
I'd like to start by getting one of you to explain a feature for me. Using Google Earth, if you set your eye position at about 400 miles altitude, there is a visible arc with Montgomery, Al at the bottom and swinging in a clockwise manner north towards Nashville, TN. What is it?
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AdminNWR Inactive Member |
Thread moved here from the Proposed New Topics forum.
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macaroniandcheese  Suspended Member (Idle past 3927 days) Posts: 4258 Joined: |
i'm no geologist. but based on my masterful powers of deduction, i'd say it looks an awful lot like the big river bed to the west and the big mountain range to the northeast. so. it's either a fault (we know there's one in alabama... it's active too. quake a year or so ago) or an old river bed.
but yes. i'm curious too.
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NosyNed Member Posts: 8996 From: Canada Joined: |
Not a geologist either, but it looks like mountain roots of what is left of the Appalachians. That is the folds caused by the crunching of NA and Europe, when was it? 250 Myrs ago or so.
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
That's definitely what we see to the north east of of Montgomery and we will get to those in a while (including the Ark which came to rest just North of Birmingham). But this is so regular, I'd like to see what the geologists say.
We'll move on up the coast as this thread progresses hopefully. This message has been edited by jar, 01-14-2006 02:35 PM Aslan is not a Tame Lion
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arachnophilia Member (Idle past 1343 days) Posts: 9069 From: god's waiting room Joined: |
zoom in a bit, and you'll see.
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Ben! Member (Idle past 1398 days) Posts: 1161 From: Hayward, CA Joined: |
Jar,
Is this link i made for Google Maps a fair representation of what you're looking at? Does it look much different from Google Earth (i.e. clearer)? I'm specifically looking at the curve to the left of the vertical blue direction sign. Ben
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Yes, the arc to the west of your line.
Aslan is not a Tame Lion
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roxrkool Member (Idle past 988 days) Posts: 1497 From: Nevada Joined: |
If it gets people interested in geology, Google Earth is a good thing, Jar.
What you're looking at are Cretaceous rocks (the arc) that separate the southern Appalachians on the east from the Mississippi Embayment on the west. The following link should help: The Ouachitas Ed. To fix geography. This message has been edited by roxrkool, 01-15-2006 12:00 AM
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Asgara Member (Idle past 2302 days) Posts: 1783 From: Wisconsin, USA Joined: |
That is a fascinating site rox, thanks.
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Great. Wonderful answer.
But I'd like to get a little more information from you if I can before we move north a ways. How was the arc created? Aslan is not a Tame Lion
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NosyNed Member Posts: 8996 From: Canada Joined: |
When the old continents collided and pushed up the appalacians?
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Well, was hoping for a little more detail than that.
Aslan is not a Tame Lion
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roxrkool Member (Idle past 988 days) Posts: 1497 From: Nevada Joined: |
Im getting a little out of my league here, but I'll take a shot at it.
The Appalachians/Ouachitas/Ozarks are formed from several orogenic events culminating when the North American continent collided with Africa and South America a couple hundred million years ago. Following that collision, they began to wear down from erosion. Sometime later (just prior to the Cretaceous), the three continents separated via rifting and the Mississippi Embayment formed as a reactivation of a previous rift zone (though I'm not sure if that was a failed rift). Since the NA continent didn't split along the MS Embayment, it's considered a failed rift zone and this is the reason for the New Madrid Seismic Zone. When rifts form, however, the ground starts to subside until eventually the ocean is allowed to inundate. So this likely happened in the embayment to some degree, but also, during the Cretaceous, sea level was rising and so the failed rift/embayment was inundated with marine waters. This sea level rise also formed the Western Interior Seaway from Texas, through Colorado/Nebraska, and up into Canada. When sea level decreased, the embayment became a major drainage basin. The arc is likely an artifact resulting from the erosion of the Appalachian highlands, deposition of Cretaceous sediments against the highlands, uplift, and finally erosion by the Mississippi River. Hopefully coragyps or edge can confirm or correct the above. I believe they are both quite familiar with the area. This message has been edited by roxrkool, 01-18-2006 09:03 PM
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roxrkool Member (Idle past 988 days) Posts: 1497 From: Nevada Joined: |
You're welcome. It's one of my favorite.
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