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View Diary: 13 Maps from My Collection. Any Surprises? (144 comments)

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  •  The Rockies formed after this? (5+ / 0-)

    I was wondering about that.

    •  oh yes (10+ / 0-)

      the Rockies are built up long and slow through the ages colliding all kind of flotsam that the palaeo-Pacific brought, with the laurentian edge. For that you first had to have Laurentia.

      The transcontinental arch (which is responsible for the famous iron ore deposits in Michigan´s upper peninsula) dates back to the making of Laurentia itself. It was the old backbone of the craton, as it were (further north, in northern Canada, my knowledge stops)

      The transcontinental arch predates the time when the earth was hidden in a snowball. It comes from the time when the first traces of oxygen (well, then already substantial ones) were dropping the dissolved iron out of solution in the oceans. (Making your Keewenawan iron ores).

      yeah well, and now, it is a featureless flat plain - on which one can film things like the airplane hunt scene in this Chicago movie. That is downright depressing a fate for such a storied feature.

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