Monday, February 21, 2011

My World: Rock Bluff (Ozarks Geology)

Rock bluff along the route of a recent afternoon walk.

I usually say I live in the Ozark Mountains, but "mountain" is a generic term largely based upon appearance.  If you have hills and valleys, the combination of the two is called "mountains".  In geologic terms, it would be more correct to say I live on the Ozark Plateau because the Ozarks are actually a dissected plateau.  Most mountain ranges were formed when geologic events -- like the collision of tectonic plates -- caused the earth's crust to buckle and fold, uplifting mountains and leaving valleys between them. By contrast, the entire area known as the Ozarks (northern Arkansas, southern Missouri, a bit of eastern Oklahoma and a tiny corner of southeastern Kansas) was uplifted as a plateau with relatively little buckling and folding..  Over millions of years since the uplift, valleys eroded into the plateau leaving hills behind.  

Being a dissected plateau gives the Ozarks some unique features.  Our mountain tops tend to be flat.  The decent into valleys is rugged and steep.    The various strata of sedimentary rock deposited before the Ozark Plateau was uplifted remain in place just like they were laid down millions of years ago. There is little of the scrambling of strata that occurs when the earth's crust is folded and buckled.  Geologist can easily follow a particular rock stratum over a wide geographic area.

Overview of the Ozark Plateau and its four main regions.  (Wikipedia)

Side Note:  The origin of the name "Ozarks" is disputed.  Many think it is a linguistic corruption of  the French abbreviation aux Arks (short for aux Arkansas, or "of Arkansas" in English) which originally referred to the French trading post at Arkansas Post, but eventually came to refer to all Ozark Plateau drainage into the Arkansas and Missouri Rivers.  Other possible derivations include aux arcs meaning "of the arches" in reference to the dozens of natural bridges formed by erosion and collapsed caves in the Ozark region.  (Source:  Wikipedia)

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Lisa at Greenbow said...

I don't know all the science about your area Marvin but I do know it is a beautiful part of the world.

Kathie Brown said...

Pretty interesting stuff. I never knew any of this! Happy MWT! Love the rocky bluff picture. Looks similar to rock outcroppings in New England.

Pat - Arkansas said...

I enjoyed the geology lesson and, surprisingly, understood quite a bit of it! :)

Your rock bluff is beautiful.

Lana Gramlich said...

Thanks for all of the info. I know the area's lovely, but never looked into it much, I must admit.

Anonymous said...

I had no idea that mountains were so complicated. I think I'll continue to think of the Ozarks as mountains, regardless.

PS I'd like to think there was a lost armadillo rooting around in my yard, but I think they're all smart enough to stay far away from Michigan in the winter time.

Unknown said...

I grew up a barefoot hillbilly. :) I do miss the bluffs and am always amazed at all the undergrowth that happens down there when I come back home to visit family.

EG CameraGirl said...

Very interesting, Marvin. Firstly, I didn't know the tops of the Ozarks tend to be flat, and secondly dissected plateau is a new term to me.

I know very little about your area's geography.

Barb said...

A great geology lesson, Marvin. I never realized your area is considered a plateau.

Johnny Nutcase said...

Cool post, Marvin. Geology is so interesting! I really like rock bluffs too. I grew up in TN and there were some nice ones there. We're in Mississippi now and there are NO rocks..anywhere. Booo!