Chapter 9 - Geological Time

What is the source of natural carbon-14? Nuclear fission of the heavy, radioactive elements uranium and thorium Fusion of hydrogen and helium in the Sun and eruption of solar flares Leakage of radioactive gases from the liquid, outer core Cosmic ray collisions and neutron-capture involving atmospheric nitrogen

Cosmic ray collisions and neutron-capture involving atmospheric nitrogen

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? Eon, era, epoch, period Era, period, epoch, eon Eon, epoch, period, era Eon, era, period, epoch

Eon, era, period, epoch

The radioactive isotopes uranium-238, uranium-235, and thorium-232 eventually decay to different, stable, daughter isotopes of ___________. Iron Argon Strontium Lead

Lead

Which of the following refers to the process of fossilization where the pores of the original plant or bones of an animal are filled with precipitated mineral matter? Petrification Internal and external molds Carbonization Impression

Petrification

Which of the following refers to the idea or concept that ancient life forms succeed one another in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata? Principle of cross correlation Law of fossil regression Law of correlative indexing Principle of faunal succession

Principle of faunal succession

With regard to the illustration below, which of the following statements is correct? Sill 'D' was intruded between beds 'C' and 'E' after deposition of 'E' Dike 'F' was emplaced after development of the angular unconformity just below bed 'G' Tilting of beds 'A' through 'E' occurred after deposition of beds 'G' through 'K' Bed 'B' is younger than bed 'C' Sill 'D' is younger than dike 'F'

Sill 'D' was intruded between beds 'C' and 'E' after deposition of 'E

An unconformity is a buried... Fault or fracture with older rocks above and younger rocks below Surface of erosion separating younger strata above and older strata below Fault or fracture with younger strata above and older strata below Surface of erosion with older strata above and younger strata below

Surface of erosion separating younger strata above and older strata below

Which of the following best characterizes an angular unconformity? Tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity. Horizontal lava flows lie below the unconformity and horizontal, sedimentary strata lie above. The discordant boundary between older strata and an intrusive body of granite. Tilted strata lie above the unconformity with loose, unconsolidated soil below.

Tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity

Question 22 What is the age of the Earth accepted by most scientists today? 6.4 billion years 4.5 million years 4.5 billion years 4500 billion years

4.5 billion years

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? Bed 5 is the oldest Beds 1 and 3 are older than bed 4 Bed 4 is older than bed 2 Bed 3 is older than both beds 2 and 4

Beds 1 and 3 are older than bed 4

Most sedimentary rocks are readily dated by radiometric methods. True False

False

Which of the following is an essential characteristic of an index fossil? The organism lived only in specific, geographically restricted, environments such as lakes or estuaries The specific life form only existed for a short range of geologic time The specific life form spanned a large range of geologic time The fossils occur in deep-water marine sediments, but the organism actually lived on beaches

The specific life form only existed for a short range of geologic time

A disconformity is an erosional unconformity with parallel beds or strata above and below. True False

True

What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? Law of superposition Principle of lateral continuity Principle of cross-cutting relationships Principle of original horizontality

Law of superposition

The proportion of parent to daughter isotopes in a radioactive decay process is 40% parent and 60% daughter. How many half-lives have elapsed since the material was 100% parent atoms? Less than 1 More than 3 Between 1 and 2 Between 2 and 3

Between 1 and 2

The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal is formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today? More than one-half Between one-fourth and one-eighth Between one-half and one-fourth Between one-half and one-third

Between one-fourth and one-eighth

Rapid burial and possession of hard parts are necessary conditions for the preservation of plant or animal remains as fossils. True False

True

The term Paleozoic describes the era of ancient life forms. True False

True

Which of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks in one area with rocks of the same age at different locations? Relative dating Correlation Absolute dating Compaction

Correlation

Which of the following describes radioactive decay by beta particle emission? The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same. The mass number of the daughter isotope is one more than the parent and both isotopes have the same atomic number. The daughter isotope has an atomic number two less than the parent and a mass number four less. The daughter isotope has an atomic number one less than the parent and a mass number two less

The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same.

Which of the following observations would not bear directly on working out the sequence of geologic events in an area? Inclusions of sandstone in a granite pluton A well-exposed basaltic dike cross-cutting sandstone The feldspar and quartz contents of a granite An unconformity between a granite and sandstone

The feldspar and quartz contents of a granite

Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically? The sandstone is younger if the granite contains sandstone inclusions The sandstone is younger if it shows evidence of contact metamorphism from the granite The granite is older if the sandstone contains pebbles of the granite The granite is older if it contains inclusions of sandstone

The granite is older if the sandstone contains pebbles of the granite