Ch. 18 Geologic Time

An uncomformity is buried __?__

What best describes angular unconformity?

In the late 1700s, James Hutton published his important work titled __?__

Sandstone strata and a mass of granite are observed to be in contact. Which means?

__?__ is an erosional contact 'tween the tilted, older strata below and horizontal, younger strata above.

The subdivision of geologic time scale that represent the longest time span is called a(n) __?__

The ration of parent to daughter isotopes in a radioactive decay process is 0.40. How many 1/2 lives have elapsed sice the material was 100% parant atoms?

Consider the names of eras in the geologic time scale. What is meant by "zoic"?

Assume that you have just examined several flat-lying sedimentary layers. After much study you determind that there is a considerable span of time for which no sedimentary rock layer exists at the site. You have just discovered a __?__

A worm would stand a poor chance of being fossilized because __?__

What fundamental concept states that in a horizontal sequence of conformable sedimentary strat, each higher bed is younger than the bed below it?

What refers to the investigative process by which geologist identify and match sedimentary strata and other rocks of the same ages in different areas?

The __?__ is the idea or concept that acncient life forms succeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata?

What is an essential characteristics of an index fossil?

By applying the law of superposition __?__ dates can be determined.

The era of "ancient life" is the __?__ era

About 88% of geologic time is represented by the time span called the __?__.

What is the age of the Earth accepted by most scientist today?

Which of the following is not a very long-lived, radioactive isotope?

The 1/2 life of C-14 is about 6000 years. Assume that a sample of charcoal formed by burning of living wood 15,000 years ago. How much of the original C-14 would remain today?

Visualize five horizontal sedimentary strata exposed in a cliff or canyon wall indentified by consecutive numbers, 1 being the lowest bed and 5 being the highest. What statement would be true?

Era know as the "age of mammals" is the __?__ Cenozoic

Blocks of rocks enclosed in a body of younger igneous rock?

Buried, erosional surface where rock layers are missing?

Kind of unconformity is produced when tilted, older strata are eroded and buried by younger strata?

Process involves identifying and matching rocks of similar ages in different areas?

Name of Phanerozoic era that means ancient life?

"The present is the key to the past" refers to the doctrine of