Exam 16: Geologic Time: Concepts and Principles

A fossil that is particularly useful for correlation is an evolutionary fossil.

Which of the major rock types were most important originally in developing the geologic time scale, and why?

An interval of geologic time not represented by strata in a particular area is a(n) ____________________.

Carbon 14 is useful for archeological purposes because it can effectively date samples back to approximately ____________________ years.

What were some of the ways early scholars tried to determine the age of Earth?

Fossils are found almost exclusively in sedimentary rocks.

Long-lived parent-daughter isotope pairs have half-lives of thousands to hundreds of thousands of years.

What is the principle of cross-cutting relationships?

What sort of instrument is used to determine the parent-daughter ratio of isotopes, and what does it measure?

What other attributes do ashfalls provide in serving as excellent marker beds?

How were absolute ages added to the geologic time scale in the 20^th century?

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

The age of the Earth is:

How was the geologic time scale developed in the 19^th century?

When radiometric dating is applied to metamorphic rocks, the date obtained is:

All radioactive elements decay in only one decay step.

Long-lived radioactive isotope pairs used in radiometric dating have half-lives of the magnitude of ____________________ or ____________________ of years.

Potassium 40 decays to argon 40 by a single electron capture.

____________________ dating is used to obtain absolute age dates.

A surface of discontinuity representing a break in the depositional record; a discontinuity representing erosion or nondeposition is a(n) ____________________.