Does the law of crosscutting relationships involve sedimentary rock only? Why or why not?

1 Answer
Dec 27, 2016


No, it does not only involve sedimentary rocks.


Why? It's because igneous rocks can also cut through, as a result of a pluton intruding through the preexisting rock.

It is simply a relationship between two features - not exclusive to sedimentary rocks - that aids researchers in determining the relative dates of both features.

The "cutting" can be represented by a volcanic dike, for example, which is composed of igneous rock. In this case, the dike would be the younger of the two rock types, therefore establishing a relative age of each rock (this means that I can reasonably say that the igneous rock is relatively younger than its neighboring strata).

Take a look at the picture below for an example of an extrusive igneous rock cutting through a relatively large and older sedimentary outcrop.

Miguel Vera León