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: