Happy Postcard Friendship Friday, with our lovely Hostess Marie.
From the back of the card:
"The geology of Oklahoma was formed through millions of years when rocks that represent each geologic time period were deposited. Sedimentary rocks dominate exposures across the state, with major areas of igneous-rock outcrops located in the Arbuckle and Wichita Mountains of south-central and south western Oklahoma. The Oklahoma Geological Survey was formed in 1908 to investigate the geology, the energy-, mineral-, and water resources of the State and to make the results available to the public."
First of all, the 'mountains' of Oklahoma are really ranges of hills. The prairie are so flat though, they must have looked impressive.
The red colors on the map are old, uplifted igneous rocks. The tan and green colors are the various sedimentary rocks. The squiggles of yellow are recent river deposits - everything since about the Ice Ages is recent to a geologist!
The cross-sections at the bottom contain some important information. This is a view sideways through the crust and you can see the bending and folding of the layers. (How do they know this? Interpretation of seismic or earthquake studies.) The Anadarko and Arkhoma basins have produced a lot of petroleum, and continue to produce oil and lots of natural gas, which is Oklahoma's main petroleum product. An overview on how these resources formed is described on a Survey webpage. Oklahoma is not living in the past however. They are investigating wind energy too.