Chapter 12 (GEOL107)

Identify the true statement. Choose one: A. Time zones are 15° of latitude wide. B. Denver (latitude 40°N, longitude 105°W) is 10 time zones away from Greenwich, England (latitude 51°N, longitude 0°). C. Time zones are set in relation to the time at the astronomical observatory in Greenwich, England. D. The second (as a unit of time) is defined in terms of energy changes within the chromium atom.

C. Time zones are set in relation to the time at the astronomical observatory in Greenwich, England.

"The present is the key to the past" best describes the principle of... A. original horizontality. B. superposition. C. uniformitarianism. D lateral continuity. E. inclusions.

C. uniformitarianism.

Charcoal (burned wood) that was used to make prehistoric drawings on cave walls in France was scraped off and analyzed. The results showed 4 mg carbon-14 (parent isotope) and 60 mg nitrogen-14 (daughter isotope). The half-life of carbon-14 is 5,730 years. How old are the cave drawings? Choose one: A. 17,190 years B. 11,460 years C. The sample is too old to be analyzed by carbon dating. D. 22,920 years

D. 22,920 years

Which of the following lists the four time divisions in order from oldest to youngest? Choose one: A. Proterozoic, Mesozoic, Archean, Cenozoic B. Hadean, Cenozoic, Mesozoic, Proterozoic C. Phanerozoic, Proterozoic, Mesozoic, Cenozoic D. Proterozoic, Paleozoic, Mesozoic, Cenozoic

D. Proterozoic, Paleozoic, Mesozoic, Cenozoic

Why are geologists not able to date sedimentary rocks directly? Choose one: A. Sedimentary rocks are older than their composite minerals. B. Sedimentary rocks are too fine-grained to accurately date. C. Sedimentary rocks are too coarse-grained to accurately date. D. Sedimentary rocks are younger than their composite minerals.

D. Sedimentary rocks are younger than their composite minerals.

An area of slightly dipping sedimentary rock layers has large inclusions and is intruded by an igneous dike. By applying the basic principles for determining relative ages, decide which of the following is the true statement. Choose one: A. The sedimentary layers were deposited on an angle, creating the "dip" of the layers. B. The dike is older than the sedimentary rock layers it cuts across. C. The youngest sedimentary layer is the bottom layer. D. The igneous intrusion (the dike) "baked" (metamorphosed) the sedimentary rock that it touched.

D. The igneous intrusion (the dike) "baked" (metamorphosed) the sedimentary rock that it touched.

Before the development of isotopic dating methods, scientists estimated the age of the Earth by Choose one: A. counting tree rings. B. estimating eruption rates of volcanoes. C. determining the time it takes to create fossils like shark teeth. D. comparing rates of change on the Earth's surface today with the geologic record.

D. comparing rates of change on the Earth's surface today with the geologic record.

The boundary surface between two stratigraphic formations is called a Choose one: A. key bed. B. marker bed. C. nonconformity. D. contact.

D. contact.

Which of the following accurately ranks the subdivisions of geologic time in order from largest to smallest? Choose one: A. epoch, period, eon, era B. period, era, eon, epoch C. era, eon, epoch, period D. eon, era, period, epoch

D. eon, era, period, epoch

If you equate all of the Earth's history to one calendar year, the history of our species (Homo sapiens) would occupy Choose one: A. the time from December 15 to New Year's Eve. B. the time from December 31 at 3 P.M. to New Year's Eve. C. the week from Christmas to New Year's Eve. D. the last hour before midnight on New Year's Eve.

D. the last hour before midnight on New Year's Eve.

Nicolas Steno's observations of fossil shark teeth convinced him that Choose one: A. the physical processes that produce the geologic features of today operated in the past to produce the same types of geologic features. B. these were tongues of mythical dragons. C. geologic features develop by a series of events over periods of time shorter than human history. D. the rock they were in originated as loose sand, not solid rock.

D. the rock they were in originated as loose sand, not solid rock.

A hominin (human family) skull was found in a shale layer between two fine-grained igneous rock layers. There were no baked zones on the rocks above the igneous layers. The skull had been 100% fossilized and changed to stone; there was no original skull material left. On the basis of this information, decide which of the following statements is true. Choose one: A. The shale layer can be dated by radiometric methods. B. The skull itself cannot be dated, because it is no longer organic material and it is not igneous material. The age of the skull is determined by its position between the igneous layers. C. The igneous layers must be intrusions such as dikes, because they are fine-grained rock and there are no baked zones on the rock above them. D. The skull should be dated by the carbon-14 method, since this is the method used for organic material older than 1 million years.

B. The skull itself cannot be dated, because it is no longer organic material and it is not igneous material. The age of the skull is determined by its position between the igneous layers.

Which of the following statements is true? Choose one: A. The generally accepted age of the Earth is 4.56 million years. B. Varieties of an element that differ only in the number of neutrons are called isotopes. C. A paleosol is a rock layer identified by such factors as rock type and approximate geologic age. D. An unconformity is a break in the rock record indicating that the area was underwater for millions of years.

B. Varieties of an element that differ only in the number of neutrons are called isotopes.

Identify the true statement. Choose one: A. Isotopic dating can be used only in a closed system, where neither parent material nor daughter material has escaped. B. The "radiometric clock" starts when a radioactive mineral warms above its closure temperature. C. Scientists can date any radioactive material back only three half-lives; after this, there's not enough parent material left to measure. D. Carbon-14 dating is used to date anything that was once alive, regardless of age.

A. Isotopic dating can be used only in a closed system, where neither parent material nor daughter material has escaped.

Which of the following is a method used to determine numerical age? Choose one: A. counting ice bands in a glacier B. cross-cutting relations C. correlating strata D. fossil correlation

A. counting ice bands in a glacier

An eroded granite covered by flat-lying sedimentary rocks is an example of a(n) A.nonconformity. B.disconformity. C.inclusion. D.angular unconformity. E.marker bed.

A.nonconformity.

Which of the following lists fits the order of these three descriptions: Age of Mammals, Age of Dinosaurs, and longest geologic time period. Choose one: A. Cenozoic, Hadean, Paleozoic B. Cenozoic, Mesozoic, Precambrian C. Mesozoic, Cenozoic, Paleozoic D. Mesozoic, Cenozoic, Proterozoic

B. Cenozoic, Mesozoic, Precambrian

Identify the true statement. Choose one: A. Charles Lyell correctly explained how fossils form, and he formulated some of the basic principles of relative dating. B. Henri Becquerel discovered principles of radioactivity, which led to the determination of the Earth's age. C. Archbishop James Ussher introduced the principle of uniformitarianism. D. James Hutton, the father of geology, added up generations of patriarchs in the Bible and concluded that the birth date of the Earth was October 23, 4004 B.C.E.

B. Henri Becquerel discovered principles of radioactivity, which led to the determination of the Earth's age.

Uniformitarianism Choose one: A. means that the Earth's surface (its oceans, continents, and atmosphere) has always been the same and always will be the same. B. can be illustrated by scientists' seeing pillow lava forming only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater. C. means that neither the scientific past nor the future should be predicted, because physical laws change over time. D. is an outdated theory stating that catastrophes like major volcanic eruptions no longer happen.

B. can be illustrated by scientists' seeing pillow lava forming only underwater, then theorizing that pillow lava found high in the mountains today did nevertheless form underwater.

Which of the following methods for determining the age of materials is a radiometric dating technique? Choose one: A. magnetostratigraphy B. fission-track analysis C. dendrochronology D. analysis of seasonal changes in growth rings in travertine deposits and shelled organisms

B. fission-track analysis

In 1815, William Smith correlated strata from many locations and plotted the information on paper to show the spatial distribution of rock units on the Earth's surface. This document was the first modern Choose one: A. geologic time scale. B. geologic map. C. geologic column. D. stratigraphic column.

B. geologic map.

Geologists base their estimate that the Earth is 4.56 billion years old on Choose one: A. relative age dates on clastic zircons from Australia. B. isotopic dating of meteorites thought to be from primitive solids of the early Solar System. C. age estimates of Moon rocks. D. radiometric age dates on rocks from the Canadian craton.

B. isotopic dating of meteorites thought to be from primitive solids of the early Solar System.

The principle of original continuity says that Choose one: A. in a sequence of sedimentary beds, the oldest is on the bottom. B. sedimentary layers began as continuous expanses of sediment. C. the feature doing the cutting is younger than the feature it cuts. D. rock containing inclusions is younger than the inclusions.

B. sedimentary layers began as continuous expanses of sediment.

In this image, we know that sedimentary unit A is older than sedimentary unit B because of the principle of... A. original horizontality. B. superposition. C. uniformitarianism. D. lateral continuity. E. inclusions

B.superposition.

A radioactive isotope of the element potassium decays to produce argon. If the ratio of argon to potassium is found to be 7:1, how many half-lives have occurred? Choose one: A. 1 half-life B. 7 half-lives C. 3 half-lives D. 8 half-lives

C. 3 half-lives

Identify the statement that is true about radiometric dating. Choose one: A. Dating of an individual sand grain in a sandstone accurately dates the sedimentary rock's formation. B. It can begin only when the isotopes heat up enough to decay. C. Dating of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved. D. It can be used only if some uranium is present in the rock.

C. Dating of metamorphic rock tells when the high temperatures of metamorphism cooled below the closure temperatures of the minerals involved.

A corpse with flesh intact, found in the Alps in 1991, was dated by the carbon-14 method and showed a parent-daughter isotope ratio of approximately 1:1, with slightly more parent material than daughter material. The half-life of carbon-14 is 5,730 years. On the basis of this information, decide which of the following statements is true. Choose one: A. The age could logically be 5,730 years. B. The age could logically be 6,000 years. C. The age could logically be 5,300 years. D. Since the body was still organic and had not been petrified, it was inappropriate to use the carbon-14 process.

C. The age could logically be 5,300 years.

The oldest known mineral grain is a 4.4-million-year-old zircon crystal found in an ancient sandstone. Which of the following statements applies to this zircon grain? Choose one: A. The sandstone is 4.4 billion years old. B. The sandstone is older than 4.4 billion years old. C. The sandstone is younger than 4.4 billion years old. D. It is impossible to determine the relative age of the sandstone given this information.

C. The sandstone is younger than 4.4 billion years old.

Identify the statement that is true about William Smith's observations. Choose one: A. They led to the principle of cross-cutting relations. B. Smith noted that a fossil species could disappear and then reappear in much younger strata. C. They revealed that groups of fossil species (fossil assemblages) occurred in limited intervals of strata. D. His observations of igneous intrusions in the English countryside helped develop the coal industry.

C. They revealed that groups of fossil species (fossil assemblages) occurred in limited intervals of strata.