Group Activity : LUSENET : Introductory Geology, Oswego State : One Thread

On the group activity we did in class last week i was a little confused on why A was older than B. In class I had trouble in class hearing the explination.

-- Trisha Earl (, April 04, 2001


A is older than B, because B is a diorite sill which is an igneous intrusion. An intrusion can only cut across rock that is already there. As it says in the notes in the chapter of geologic time--- "Any feature that cuts across rocks is younger than the youngest rock that is cut." If there wasn't this igneous intrusion, then A would be the youngest.

-- Sandra Feocco (, April 05, 2001.

Moderation questions? read the FAQ