Exam 16: Geologic Time: Concepts and Principles

What is the principle of superposition,and what is its importance? Who is credited with discovering it?

A sedimentary rock that shows evidence of contact metamorphism must be ____________________ in age than the igneous rock with which it is in contact,even if it lies above the igneous rock.

When a stalagmite has an oxygen-18 to ____________________ ratio that is low,the climate at the time the stalagmite formed was relatively ____________________

Different varieties of an atom that have a different number of neutrons in their nuclei are ____________________.

To determine the radiometric age of a rock,scientists must be able to measure very accurately the:

What is the principle of cross-cutting relationships?

Carbon 14 is useful for archeological samples because it is effective back to approximately ____________________ years.

The principle of ____________________ states that rock layers extended laterally in all directions unless or until they terminate in one of a number of natural means.

What is carbon-14 dating useful for in terms of age and type of sample?

The most accurate radiometric dates are obtained from ____________________ rocks.Only in very unusual circumstances can ____________________ rocks be radiometrically dated.