Test 7

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

The percentage of radioactive isotope remaining in a radioactive decay process is 40%. How many half-lives have elapsed since the material was 100% parent atoms?

The half-life of carbon-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 carbon-14 would remain today?

When a radioactive isotope decays by electron capture, the electron ________

Which of the following describes radioactive decay by beta particle emission

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

Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest?

Who is credited with formulating the doctrine of uniformitarianism?

About 88 percent of geologic time is represented by the time span called the __________

The subdivision of the geologic time scale that represents the longest time span is called a(n) _________

The ________ is the concept that ancient life forms evolved in a definite order and therefore their fossils can help determine the geologic ages of strata.

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

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

By applying the law of superposition _______ dates can be determined.

An unconformity is a buried ________

____ is an erosional contact between tilted, older strata below and horizontal, younger strata above.

Which of the following best characterizes an angular unconformity?

Assume that you have just examined several flat-lying sedimentary layers. After much study you determine that there is a considerable span of time for which no sedimentary rock layer exists at this site. You have just discovered a(n) _______

Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically?

Visualize five, horizontal, sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true?

The era of "ancient life" is the _______ era.

Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time?

Which of the following is an essential characteristic of an index fossil?

A worm would stand a poor chance of being fossilized because _________