LATERAL CONTINUITY

Material forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way." Steno, 1669

Note that the Oligocene age (~25-35 Ma) White River Group layers are not only horizontal but are also laterally continuous. By "laterally continuous", we infer that rock layers were deposited over a large area. Also note the effects of erosion. Over the past few million years, the White  River Group has been exposed to wind and water erosion such that once continuous layers are now isolated. The isolated outcrop that Patrick is touching is an erosional remnant of a once continuous outcrop. Nevertheless, we can view similar rock layers in the distance and can infer that those layers were once continuous.

Photo by Kevin Hefferan. "Scale" provided by Patrick, Kaeli and Sherri.

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