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May 8, 2016 Weekly Geology Guess

May 8, 2016
Greetings from the Bluff Park   Porch, way up yonder on Shades Mountain (1,109′) in Alabama:
With my discussion on Alabama Geology, I have gotten the geologic cart before the horse.  I have not included a basic discussion regarding rocks and all the various kinds of sedimentary, metamorphic, and igneous rocks.
We will continue with Metamorphic Rocks.

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Minerals and Rocks – The Good Life from the Ground
 
“If it ain’t grown, it has to be mined”
Metamorphic Rocks

>    This is one of the best and simple explanations of Metamorphic Rocks.


http://geology.com/rocks/metamorphic-rocks.shtml

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form”.[1] The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars),[2] causing profound physical and/or chemical change. The protolith may be a sedimentary rock, an igneous rock or another older metamorphic rock.”  Wikipedia

There are two basic types of metamorphic rocks.

For this week, we will cover Foliated metamorphic rocks such as gneiss, phyllite, schist, and slate.   These have a layered or banded appearance that is produced by exposure to heat and directed pressure.
Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance.
For a more in depth review of metamorphic rocks, go to

https://en.wikipedia.org/wiki/Metamorphic_rock

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Slate (Low Grade Metamorphism changes clay or volcanic ash to Slate)

https://en.wikipedia.org/wiki/Slate

Phyllite (intermediate Grade Metamorphic Rocks between slate and schist).  Metamorphism changed Mudstone or Shale or Slate to Phyllite)

https://en.wikipedia.org/wiki/Phyllite

Schist (Medium Grade Metamorphic Rocks).  Metamorphism changed clays and muds into Schist through a series of intermediate steps.

https://en.wikipedia.org/wiki/Schist

Gneiss (High-grade regional metamorphism)  Intense Metamorphism changes sedimentary or igneous rocks into gneiss.

https://en.wikipedia.org/wiki/Gneiss

All of these metamorphic rock types are found in the Alabama Piedmont.
See Maps in the Attachments.
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Attached is a handy guide to rocks by the USGS (US Geological Survey).  Simple in terms of Petrology, but still detailed.  R

http://geology.about.com/od/rocks/a/Rock-Tables.htm?utm_source=facebook&utm_medium=social&utm_campaign=shareurlbuttons

Thanks,
Randy
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Editors Note:  It is the intent of this site to keep this discussion as simple as possible, so as to educate the interested general public and not to discuss with the geology crowd the latest geologic theories and nuances.  Thanks, R
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“No copyright infringement intended.
The rights belong to their respective owners”
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Copyright Disclaimer: Under Section 107 of the Copyright Act 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use.

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Author’s Request:  If you see any pictures that you know the source and photographer, let me know immediately.  Thanks!  R

Images have been searched by TinEye Reverse Image Search.  http://tineye.com/

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Next week we will look at Non-Foliated Metamorphic Rocks like marble and novaculite (sharpening stones) .
 
Thanks,
R
 
 
Have A Great Week!
Randy/Randall
Metamorphism Grades

Metamorphism Grades

Slate. St. Fagans, Nat. Museum, Wales.  Tannery, Slate Roof.  08-2007.  by Zuerks

Slate. St. Fagans, Nat. Museum, Wales. Tannery, Slate Roof. 08-2007. by Zuerks

Phyllite.  Hormersdorf.  Wikimedia.org

Phyllite. Hormersdorf. Wikimedia.org

Schist, Micaceous.  12-05-2012.  by MIchael C. Rygel

Schist, Micaceous. 12-05-2012. by MIchael C. Rygel

Schist, Thin_section_of_garnet-mica. Salangen, Norway.  Jackdann88

Schist, Thin_section_of_garnet-mica. Salangen, Norway. Jackdann88

AL-VR.  Eastern Piedmont Fault System, Folded

Gneiss. Eastern Piedmont Fault System, Folded

Gneiss, Migma. 07-17-2006.  Georemgerfkprd. Norway.  Siim Sepp

Gneiss, Migma. 07-17-2006. Georemgerfkprd. Norway. Siim Sepp

Gneiss. AL. Piedmont. Oldest Gold Mine in AL, Dec09. by R. McDaniel

Gneiss. AL. Piedmont. Oldest Gold Mine in AL, Dec09. by R. McDaniel

AL Geo. Map, Piedmont

AL Geologic Map of the Piedmont

AL-P.  Loc.-Roads

Roads in the Alabama Piedmont

AL-P.  X-Section

Generalized Cross Section of the Alabama Piedmont

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