How Where They Created? (Ozark, Gasconade: earthquakes, gated, camping)

[Hillman]

Ok we have hills here but you get up where you have a good view it looks flat which tells me they were created by erosion.

Ok I went hunting and camping in Ozark County.There is predominate Hills can anyone tell me how they were created?

hillman

[Mollym313]

Originally Posted by Hillman

Ok we have hills here but you get up where you have a good view it looks flat which tells me they were created by erosion.

Ok I went hunting and camping in Ozark County.There is predominate Hills can anyone tell me how they were created?

hillman

I'm not sure how accurate I will be...but I'll take a stab at it. I took a class about these types of things. Some hills are formed by water like lakes and rivers. Ripple like hills are from difference depths of the water over time along with erosion. However some hills can be caused by earthquake/continental shifts. The Earth's plates move in different directions and push land up. The type of shift varies and the result is different patterns of hills and even mountain ranges. I know I am leaving out a lot of important stuff but that is my best recollection of the class.
I know there is a fault line over on the East side of Mo.

[MoNative34]

The area was once part of the ocean. The build up of sediment created the limestone. After that, there was an uplift creating a dome and then the area gradually eroded. Groundwater created caves, springs and sinkholes.

[Versatile]

A guy with a very big shovel! Never mind it is my nap time! lol

[Inoxkeeper]

MoNative pretty much nailed it. The Ozark Mountains are really a plateau that was once an ancient sea or inland ocean bed that has been eroded by our streams and rivers.

There is one small part of actual mountains that are the oldest in the US, the St. Francis Mountains (where my land is!). They are the "nubs" of a really old chain and were pushed up thru the Ozark plateau by seismic activity long ago.

[OA 5599]

Others have pinned it down fairly well, but here is my more detailed account (my dates may be off by 100 million years or so, however )

1. 1.5-1.4 billion years ago: the St. Francis Mountains were created by volcanic activity. Some areas (like Taum Sauk and Proffit Mountains) were created by lava flowing out of cracks on the earth's surface. These mountains are made out of rhyolite, the purple rock with white speckles you can find in that area. Other current "mountains" were created by lava cooling underneath the surface of the earth, and were subsequently exposed by erosion. These areas are made of pink granite. The same granite and rhyolite is underneath the rest of Missouri...it is just buried under younger rocks.

2. 500-300 million years ago: The sedimentary rocks that make up the Ozarks (primarily dolomite, but also quantities of sandstone, limestone, and isolated shale) were deposited in a shallow, tropical sea. The St. Francis mountains likely stood as islands above these shallow seas, and may be the only areas for thousands of miles to have never been submerged by ancient seas.

3. About 250 million years ago: South America slams into North America (plate tectonics at work!). This creates the Ouachita Mountains in Arkansas and Oklahoma, where the rocks are folded and deformed into elongated ridges. At one time the Ouachitas were about the size of the present-day Rockies. Uplift from the continental collision is less severe to the north, and gradually uplifts the present-day Ozarks as a low, flat dome. The Boston Mountains in Arkansas are uplifted far more than the Missouri Ozarks, as they are much closer to the Ouachita mountains and the continental collision. Many, many large earthquakes would have occurred during this mountain building (known as the "Ouachita Orogeny").

If you look at a map of southern Missouri you'll see that most of the streams have very curvy, meandering paths, despite being confined by valley walls of solid rock. The Gasconade River is a perfect example. What likely happened is that the ancestral Ozarks were a flat plain, barely above sea level, before being uplifted, which allowed rivers to develop and meander their way across the plain (like the present-day Mississippi in the Bootheel). When the Ozarks were uplifted (which happened slowly over millions of years), the streams kept their old, curvy courses and simply downcut to keep up with uplift.

As far as your original question Hillman, those "mountains" in Ozark County are simply uneroded layers of rock. Most of the rock in south-central Missouri is dolomite, but at one time younger layers of limestone covered the area. Most of the limestone has been eroded away by stream action, but for whatever reason, some isolated knobs of that limestone were left in Ozark and Douglas counties.

[Hillman]

Cool! I drove up on Caney Mountain looked out across there it was truly awsome unlike anywhere I think I have ever seen.

hillman

[kshe95girl]

Little known fact...... the largest limestone mines in the Western hemisphere are 60 miles south of STL.

[Inoxkeeper]

OA, Thanks for correcting my boo boo's. I have to remember to not post after copious amounts of alcohol.

One of those island is on my uncle's farm, you can see it really well on google earth...amazing topo.

[kshe95girl]

Originally Posted by Inoxkeeper

OA, Thanks for correcting my boo boo's. I have to remember to not post after copious amounts of alcohol.

I HATE whewn I do that!