Lyell Principles frontispiece, 1857 2d American edition.

Unconformity.  The surface separating the yellow "A" layer on the left, and the tilted and folded layers below, is an example of an angular unconformity.  It is a suface that represents a time interval for which no rock record is preserved at this location.  It could result from non-deposition, or from uplift and erosion.


Last revision 10/2/2015