Exam 9: Geologic Time: Concepts and Principles

What is a hiatus?

If dike A cuts across sill B, beds above and below the sill are older than A and B

What is an unconformity?

What are three types of unconformities?

Is the principle of fossil succession based on an assumption of organic evolution? Explain.

The principles of superposition, original horizontality, and lateral continuity apply to all rocks in the rock cycle.

Explain why it is possible to correlate rocks among several regions when the strata being correlated between two of the regions are not of the same age?

Assigning an age to the earth is as simple as calculating the salinity of ocean water since the salts were originally derived from continents.

Does the principle of uniformitarianism mean that nothing which has not happened in recorded history could have happened in the past? Explain.

What is a index fossil?

Describe the conditions necessary for a rock to be appropriate for radiometric dating. Which condition is most limiting relative to the reliability of given age estimate?

Well cuttings enable geologists to correlate rock units in the subsurface.

Unconformities represent a gap in time.

What are the two different frames of reference used by geologists in speaking of geologic time?

Who, by virtue of a mathematical model, concluded that Earth could not be older than 100 million years and no younger than 20 million years?

How are well logs used to correlate subsurface rocks?

Geologists have calculated that 500 million years ago, in Earth's geologic past, days were

Explain Lord Kelvin's reasoning for calculating the age of Earth? Include in your explanation the flaw(s) in his argument.

In two half-lives, 25 percent of the parent element is left.

The principle of uniformitarianism is premised on the assumption that earth processes have been the same over geologic time.