When I studied earth science, a lecturer mentioned that one of the anomalies that earth science hasn’t been able to explain is a piece of crust in the USA.

This piece of crust appeared to match very well with the crust of another continent, if turned upside down, and didn’t match the surrounding crust in the USA.

I can't find any information about this and I can't forget about it. Is there any basis for this claim?

  • $\begingroup$ Did he mention in what part of the US. $\endgroup$ Commented May 5, 2014 at 9:59
  • $\begingroup$ really sorry, cant remember, although i think he did mention it. i got the impression he was aware of only 1 such anomaly. Also I cant remember the location of the matching crust, MAYBE Africa but im really not sure. $\endgroup$
    – 497362
    Commented May 5, 2014 at 10:02
  • 1
    $\begingroup$ Could be the remainder of a nappe. If the top part erodes only a piece of upside down crust could be left over, which seems to have no direct relation to the surrounding rock. $\endgroup$
    – hugovdberg
    Commented May 5, 2014 at 10:19
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    $\begingroup$ It could also be an ophiolite, although I don't think there are any examples of these being truly upside down although they might initially appear to be so due to a fold (eg. Troodos in Cyprus - where the higher elevations represent the upper mantle) $\endgroup$
    – winwaed
    Commented May 5, 2014 at 12:54
  • $\begingroup$ FWIW, Mt. Diablo in CA is a piece of the Pacific Plate that got scraped off of it and turned upside down. Not sure if that's what you're referring to. $\endgroup$
    – BillDOe
    Commented Sep 13, 2015 at 1:37

1 Answer 1


Most probably, he was referring to the Brunswick Magnetic Anomaly: http://www.geosociety.org/news/pr/2014/14-22.htm

This is an area of lower-than-normal magnetism present in North America in the Southwestern United States. Note that altough it COULD be a piece of Africa, it could also be caused by something else.

  • $\begingroup$ My lecturer made a point of it being upside down. I want to point out that lecturers have their opinion and do employ 'lecturers license'. I realize that this answer may be what he was referring to. But I cant be sure because of his assertion about it being upside down. $\endgroup$
    – 497362
    Commented May 5, 2014 at 14:48

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