Geology "Geologic Time"

The most useful method for dating the oldest events on Earth is ____.

radiometric dating of rocks and fossils

Which statement about methods of determining Earth's age is false?

James Hutton calculated the age of Earth by measuring the rate of igneous rock formation.

Uniformitarianism is the assumption that ____.

present day geologic processes also occurred in the past

Whose work was the basis for the principle of uniformitarianism and the unavoidable necessity of a great age for Earth?

James Hutton

What is the general term for a gap in the geologic rock record that represents a period of non-deposition, erosion, or both?

unconformity

____ is the study of the composition, origin, areal distribution, and age relationships of layered rocks.

Stratigraphy

A hiatus between igneous or metamorphic rocks and sedimentary rocks is represented in the rock record by a(n) ____

nonconformity

Suppose an isotope has a half-life of 50 million years, and 1/8 of the sample remaining consists of that isotope. What is the age of the rock from which it was taken?

150 million years

A fossil is determined to be 175,000 years old. This is an example of a(n) ____ date.

radiometric

The longest divisions of geologic time are called ____.

eons

What is the approximate age of Earth?

4.6 billion years

What principle states that in an undisturbed succession of sedimentary rocks, the oldest layer is at the bottom and the youngest is at the top?

The principle of superposition

Divisions in geologic time represent ____.

distinct changes in the rock record

A clast of granite found in a conglomerate is determined to be one hundred million years old. What does this information suggest about the conglomerate?

The conglomerate is younger than 100 million years.

Radiocarbon dating is possible primarily because ____.

organisms stop accumulating carbon-14 when they die

Index, or guide, fossils are most useful because they ____.

lived during a brief period of geologic time

A rock sample containing an isotope with a half-life of 12 million years has an initial mass of 72 grams. How much of the daughter isotope will be present after three half-lives?

63 grams

____ are a type of lithostratigraphic unit with distinctive upper and lower boundaries.

Formations

What is the maximum age limit for radiocarbon dating of fossils?

70,000 years

The placement of events in a sequential order based upon their position in the rock record is referred to as ____ dating.

relative

Rock units can be correlated best by examining ____.

fossil data, rock types, and key beds

The geologic time scale was initially put together by ____.

superposition, fossil succession and correlation

Divisions in geologic time represent ____.

Radiometric dating is possible because ____.

decay constants do not change

Which principle states that fossil assemblages succeed one another through time in a regular and predictable order?

The principle of fossil succession

A half-life is the amount of time required ____.

A rock sample containing an isotope with a half-life of 12 million years has an initial mass of 72 grams. How much of the parent isotope will be present after three half-lives?

9 grams