GL 107 Earth Systems Science

K. Hannula

Study questions for 8/29/07

1.  Think of some event that you consider old.  We will put them on a geologic time line during class.

Many answers are possible.

2.  Define "relative dating."

Relative dating is a method of determining the order in which geologic events occurred, without knowing necessarily how long ago any of the events took place.

3.  Define "the law of superposition."

The Law of Superposition states that, in an undeformed sequence of sedimentary beds, the oldest beds are at the bottom and the youngest beds are on top.

4.  Define "the principle of original horizontality."

The Principle of Original Horizontality states that sedimentary rocks are generally deposited in horizontal layers, and if they are tilted or folded, they must have changed their position after they were deposited.

5.  What are "cross-cutting relationships?"

Cross-cutting relationships are a method of determining the relative age of igneous rocks and faults.  Younger igneous rocks (and younger faults) cut across pre-existing rock units.