GEO CH 10 – Flashcard
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Basaltic clasts found in a conglomerate have been radiometrically dated to 50 million years ago (Eocene Epoch of the Tertiary Period). Is this a reliable age for the conglomerate?; a. Yes.; b. No, this age is likely too old.; c. No, this age is likely too young.; d. No, basalt never contains minerals bearing radioactive isotopes
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b. no, this age is likely too old
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The last question involves the Principal of (a) cross cutting relationships (b) lateral continuity (c) superposition (d) inclusions (e) baked contacts
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d. inclusions
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According to the Principal of Lateral Continuity, a younger rock must have been deposited above an older rock (a) T (b) F
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b. false
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James Hutton, the "father of geology," put forth the principle of ____________.; a. superposition; b. original continuity; c. original horizontality; d. uniformitarianism
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d. uniformitarianism
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A billion years is years to the power of (a) 3(b) 6 (c) 8 (d) 9 (e)10
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d. 9
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The first geologists could measure (a) relative or (b) absolute ages
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a. relative
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William Smith is associated with (a) faunal succession (b) canal building (c) relative age dating (d) the first geologic map (e) all of the above
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e. all of the above
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Younger over older is (a) original horizontality (b) superposition (c) faunal succession
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b. superposition
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Siccar Point has a (a) angular unconformity (b) disconformity (c) nonconformity
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a. angular unconformity
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A gravel bed is deposited on eroded granite. Would that produce an (a) angular unconformity (b) disconformity (c) nonconformity
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c. nonconformity
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In most locations it is possible to see all of the geologic periods in the rocks below one's feet if one digs deep enough (a) T (b) F
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b. F
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The correlation of strata hundreds of miles apart is most easily done with fossils (a) T (b) F
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a. T
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William Smith was primarily working on the role of (a) an English cleric (b) a geologist (c) an engineer/surveyor (d) a paleontologist (e) a ship's master
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c. an engineer/surveyor
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A catastrophist would support the principle of original horizontality (a) T (b) F
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b. F
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If your geology was divided into pre-flood and post-flood you could be labeled a catastrophist (a) T (b) F
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a. T
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There are (a) 1 (b) 2 (c) 3 (d) 4....eons in the Precambrian
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c. 3
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We have no rock samples from the Hadean Eon in the geologic record (a) T (b) F
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a. T
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The geologic period when hard bodied life really took off was the (a) Ordovician (b) Phanerozoic (c) Cretaceous (d) Holocene (e0 Cambrian
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e. Cambrian
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Epochs are (a) smaller than (b) larger than... periods
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a. smaller than
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Would an index fossil have to be widespread (a) Y (b) N
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a. Y
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Nearly parallel strata above and below an erosional surface is a (a) nonconformity (b) disconformity (c) angular unconformity
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b. disconformity
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If the lithology and fossil content of two bodies of rock on opposite sides of a canyon are identical, then these remaining outcrops were likely physically connected at one time and formed part of an extensive, sheet-like layer of rock. This idea summarizes the principle of; a. superposition; b. original continuity; c. original horizontality; d. uniformitarianism; ;
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b. original continuity
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Relative ages expressed on the geologic time scale primarily resulted from the study of a. fossil content and spatial relationships among igneous rocks; b. fossil content and spatial relationships among sedimentary rocks; c. radiometric dating of igneous rocks; d. radiometric dating of sedimentary rocks
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b. fossil content and spatial relationships among sedimentary rocks
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Numerical ages for boundaries between time units on the geologic time scale primarily resulted from the study of _____, in conjunction with relative age data.; a. fossil content and spatial relationships among igneous rocks; b. fossil content and spatial relationships among sedimentary rocks; c. radiometric dating of igneous rocks; d. radiometric dating of sedimentary rocks.
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c. radiometric dating of igneous rocks
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Within the world's sedimentary rocks, fossils a. are rarely, if ever, found; b. are randomly distributed; c. occur in an ordered sequence;
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c. occur in an ordered sequence;
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Buried erosional surfaces between parallel sedimentary strata are termed; a. disconformities; b. angular unconformities; c. nonconformities
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a. disconfomitites
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The geologic time units best defined by massive faunal changes are the (a) periods (b) eras (c) epochs
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b. eras
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The era is the longest geologic time unit (a) T (b) F
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b. F
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Which eon of geologic time is represented by rocks containing abundant shelly fossils?; a. Archean; b. Phanerozoic; c. Proterozoic
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b. phanerozoic
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Two atoms of a single element that differ in number of neutrons are said to represent two distinct ____ of that element.; a. isomers; b. isotopes; c. isotherms; d. atomic species
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b. isotopes
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Which proportion of a radioactive isotope is expected to remain in an unaltered (unreacted) state after the passage of three half-lives?; a. one-third; b. three-halves; c. one-eighth; d. one-sixth
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c. one-eighth
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Precisely speaking, a measured radiometric age for a mineral crystal within an igneous rock denotes the amount of time that has passed since the __ a. atoms within the crystal were part of a body of molten magma; b. crystal solidified; c. temperature of the crystal became equal to the Curie point for the mineral; d. temperature of the crystal became equal to the closure temperature for the mineral
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d. temperature of the crystal became equal to the closure temperature
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Radiometric dates applied to sedimentary rocks produce ages that are ____________.; a. just as accurate as when the technique is applied to igneous rocks.; b. too young (postdate sedimentary deposition); c. too old (predate sedimentary deposition
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c. too old (predate sedimentary deposition)
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In the 1800s Lord Kelvin estimated the age of the Earth, utilizing a number of assumptions. Which wrong assumption was the primary reason why his estimate (approximately 20 million years) was so wildly inaccurate?; a. The Earth was once hotter than it presently is today.; b. The Earth may have been molten when first formed.; c. No new heat has been added to the Earth since its initial formation.; d. The Earth would lose heat over time through radiation into outer space
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c. no new heat has been added to the earth since its initial formation
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Which statement best summarizes the development of the geologic time scale?; a. Numerical ages for rocks were known well before the relative sequence of sedimentary layers was established.; b. Relative ages for sedimentary strata were known well before accurate numerical dates for these rocks could be provided.; c. Names of relative ages (such as Silurian) and accurate numerical dates for these ages appeared at about the same time
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b. relative ages for sedimentary strata were known well before accurate numerical dates for these rocks could be provided
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In an unweathered sample of detrital sedimentary rock, the ratio of an unstable isotope to its stable daughter isotope is 1/15. If no daughters were present at the time the rock cooled below closure temperature, and the half-life of the reaction is 50 million years, how old is the rock?; a. 200 million years; b. 400 million years; c. 750 million years; d. none of the above
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a. 200 million years
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The "atomic clock" most likely to be thermally reset to zero is (a) Rb/Sr (b) U/Pb (c) C14 (d) K/Ar
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d. K/Ar
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The longest half life belongs to (a) Rb87 (b) Carbon 14 (c) K40 (d) U235 (e) U238
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a. Rb87
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Can you do age dating using daughter:daughter isotope ratios? (a) Y (b) N
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a. T
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Radiometric age dates can be used where there are no suitable rocks to date radiometrically provided index fossils are present at bth the site where the radiometric age date was measures and at the site with no suitable datable rocks (a) T (b) F
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a.T
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The very oldest age dates measured in Earth's materials were (a) the age of the rocks they were measured in (b) from older rocks than in (a)
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b. from rocks older than in (a)
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Darwin had no sympathy for Uniformitarianism (a) T (b) F
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b. F
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The King James Bible used Ussher's ages for the Earth, which was to have started close to (a) 4000BC (b) 10,000BC (c)2000BC (d) AD1 (e) nonsense- no such ages are to be found there
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a. 4,0000BC
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The Cambrian Period is the start of the Proterozoic Eon (a) T (b) F
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b. F
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In U-Pb dating the Pb is a (a) parent (b) daughter
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b. daughter
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Carbon dating uses the (a) parent: daughter ratio (b) the ratio of parent to C12
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b. the ratio of parent to C12
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Uranium isotopes differ in the number of electrons (a) T (b) F
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b. F
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If a daughter is formed from a parent isotope, the number of protons must have changed (a) T (b) F
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a. T
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Is it possible to have radioactive decay actually move an element to a larger atomic number? (a) Y (b) N
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b. N
