Unit 3 Review

Front

What does the Law of Original Horizontality state?

Back

Sedimentary layers are deposited in horizontal sheets, and any tilting or folding occurs after deposition.

Front

What does the Law of Cross-Cutting Relationships indicate?

Back

The intrusion going through the layers is the youngest.

Front

What are unconformities in geology?

Back

Periods where deposition stopped and erosion took over.

Front

How do you determine the order of rock layers from oldest to youngest?

Back

By applying the Law of Superposition and identifying the correct sequence.

Front

What is the half-life of a radioactive substance?

Back

The time it takes for half of the substance to decay.

Front

If the half-life of iodine-125 is 60 days, how many half-lives pass in 180 days?

Back

3 half-lives.

Front

What is the Law of Superposition?

Back

In an undeformed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest are at the top.

Front

What does the Law of Lateral Continuity state?

Back

Layers of sediment initially extend laterally in all directions; they are not interrupted by valleys or other topographical features.

Front

What is an example of an unconformity?

Back

A gap in the geological record where erosion has removed previously formed layers.

Front

How can you identify the youngest rock layer?

Back

By using the Law of Cross-Cutting Relationships.