Friday, October 30, 2009

PFF: Geology of Montana

Nothing too creepy from me, but see Postcard Friendship Friday for more from our hostess Marie and other people playing along. I'll skip the catacombs of Paris, thank you.

Today, the big wonderful state of Montana. Haven't been to the Big Sky country? Please go, for it's really beautiful. Yellowstone is in that inside corner. Glacier National Park is not to be missed.
The legend shows igneous rocks in red and pink. Very old rocks (over 1,000,000,000 years old) are in deep orange. Lighter orange is a formation called the Belt Supergroup. This is a very thick layer of different sedimentary rocks, some with pretty coarse (boulder-sized) stream sediments. Big mountains had been uplifted nearby and were eroding in a hurry.

The blues and greens are younger, Cretaceous or the time of the dinosaurs. There are some famous fossil localities in the general area of Great Falls.

Much later, bits and pieces of the Western USA came crashing into the North American continent. In a previous post I had described mountain building as a process similar to a carpet on a hardwood floor rumpling. Here, the push was so hard and so sustained, the rocks broke along faults and slivers were pushed up on top of other pieces. Think of how you can bend a piece of wood, but if you keep bending it, it will break. The faults are shown as thin black lines, esp. in northern Montana.

The other thing to note is the white line with hash marks along it. This is the extent of continental glaciation at the height of the last Ice Age, a pretty recent event in geologic time.
Ok, enough geology, I can see your eyes glazing over. Remember, there's a quiz next Friday! ;-)

Thursday, October 15, 2009

Postcard Friendship Friday - Postcard of Bedrock of Nebraska

Hello everyone to one of my favorite memes, hosted by our wonderful leader Marie, at Vintage Postcards.

Remember I am going through the USA from generally east to generally west, so hold on please for Montana and California.

We have the cut away block diagram and the legend or key on the right side, with youngest rocks (yellow orange) on top and older rocks (greens, then blues) on the bottom. Gee, just like the rock layers in Nebraska.

From the back:

"Block diagram of Nebraska Geology, on front, is available in The Groundwater Atlas of Nebraska from the Conservation and Survey Division, as is the Geological Bedrock Map of Nebraska and other maps and publications.

Nebraska Geological Survey
Conservation and Survey Division
113 Nebraska Hall
University of Nebraska-Lincoln

Well! In the center of the continent there are many layers of flat-lying rocks. The bright pink at the bottom represents the old old basement rocks of the Precambrian. The thick gray layer is the Pierre (pronounced 'peer') Shale, named after the city in South Dakota, which after all is the state just north of Nebraska.
The rolling plains of the American West is here, especially in the Sandhills region of north-central Nebraska. See these beautiful photos of this area. I have driven through here, and it is a beautiful place, empty of humans, but full of grass, sky, and wind.
And FYI: Willa Cather spent her formative years in Red Cloud, Nebraska.

Thursday, October 8, 2009

Bedrock geology of Wisconsin PFF

With our lovely hostess Marie at Vintage Postcards. Her postcard and story this week ... Shocking!

Not so shocking: Bedrock Geology of Wisconsin

From the back: :An example of one of many maps available from the Wisconsin Geological and Natural History Survey. Write to the M.A.P.S. Office for a free list of publications.
Geological and Natural History Survey, 3817 Mineral Point Road, Madison, Wisconsin. "

Here in Wisconsin there are older flat-lying layers of sedimentary rocks of Devonian and Ordovician in age, but also some much older rocks. See the geologic time scale on this web page. There is also a PDF (handy when reading my blog ;-) )

Those purple and lavender rocks in northern Wisconsin are about 1000 million years old! The patches of orange are even older, about 2500 million years old! These rocks have been metamorphosed and folded - hard to escape that when you have been around so long.
There is an area in west-central Wisconsin that was not covered by ice during the last glaciation event in the Ice Ages. How do they know? because there are no piles of glacial sediments as there are in most parts of North America, and Northern Europe and Asia too. This is still pretty difficult to explain.
Catch up on your geology postcards:


Tuesday, October 6, 2009

Bedrock Geology of Illinois

From the back:
Sedimentary rocks ranging in age from about 510 million (Cambrian) to 290 million (Pennsylvanian) are at the bedrock surface in Illinois and were deposited in and near ancient fluctuating seas. Cretaceous sands and gravels deposited in extreme southern and western Illinois are about 100 to 66 million years old. Tertiary rocks were deposited as coastal plain and deltaic sediments between 66 and 2 million years ago. Coal, oil and gas, building stone, fluorite, clays, groundwater and other resources in the bedrock contribute several billion dollars annually to the Illinois economy.

Illinois Geological Survey, 615 East Peabody Drive, Champaign, Illinois.

In Europe, The time period correlating to the Mississippian and Pennsylvanian periods is known as the Carboniferous. It was a time of great swamps, both in physical extent and how long they lasted. Large amounts of plant material were deposited, which later changed to coal. Half of the USA’s electricity is generated from Coal-fired power plants, so this is still a major commodity. (It sells for $40 - $50 a short ton – don’t ask what a short ton is!) See more information (LOTS more) at the Energy Information Administration

Fluorite is a mineral with the chemical composition CaF2 – calcium fluoride. It is mined for the fluorine for industrial purposes.

We are in the heart of the continent – lots of flat-lying sedimentary rocks here.


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