Draw (construct) a version of te geologic time scale (include eons and eras). Label the ages of the boundaries between all eons and eras.
What are "transgression" and "regression", and where are we most likely to see their effects.
What possible processes can lead to rise or fall of sea level on earth?
Take a look at Figure 6.8. The map indicates that a 100-m rise in sea level would flood more land around the East Coast and Gulf Coast of Mexico than it would along the West Coast. Why do you think this is?
Suppose a crystal of zircon crystallizes from granite magma. The zircon contains 10,000 atoms of 235U. a) after 2112 million years, how many atomsof of 235 U illbe left? (use table 6.1 for help). b) If there is no 207Pb in the ziron to start with, home many atoms of 207Pb will there be after 2112 million years?
Compare figures 6.10, 6.13 and 6.15. Why do you think that the boundaries between geologic periods correspond quite closely with significant extinctions and falls in sealevel, occassionally producing major unconformities?
1) Before the work of James Hutton, early Biblical scholars estimated the age of the Earth as about A) 6,000 years. B) 6 million years. C) 100 million years. D) 1800 thousand years. E) a month of Sundays.
2) Lord Kelvin's estimates for the age of the Earth were revised by the discovery of A) the cotton gin. B) radioactivity. C) solar energy. D) specific gravity. E) the Industrial Revolution.
3) The concept that geological processes operating now are the same processes that operated in the geologic past is the principle of A) past relationships. B) universalism. C) geologic time. D) uniformitarianism. E) uninterestedtarianism.
Match one of the eras in A through D with the geologic periods below.
4) Triassic A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic
5) Cambrian A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic
6) Permian A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic
7) Quaternary A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic
8) Cretaceous A) Precambrian B) Paleozoic C) Mesozoic D) Cenozoic
9) Lord Kelvin's estimate for the age of Earth was wrong in part because A) he assumed that all heat loss is caused by conduction. B) he deliberately disregarded radioactive decay as a source of heat loss. C) carelessly introduced simple mathematical errors into his calculations. D) he underestimated the influence of heat gain by meteorite impacts. E) All of the above are correct.
10) Uniformitarian principles used to calculate the age of Earth were not totally appropriate because A) geologists of the time had a poor understanding of sandstone deposition. B) igneous rocks were thought to have precipitated from seawater. C) the rates of geological processes are not constant. D) radioactivity, which had been discovered prior to the development of uniformitarianism, gave a very old age for Earth. E) Hutton's viewpoint strongly favored those of Ussher.
11) Extinct fossils can be used in determining relative ages of rock units. Distinctive fossils used for this purpose are called index fossils. The best index fossils would have which of the following attributes? A) short-lived in a specific geological period B) long-lived over several geological periods C) lived in only a very small area on Earth D) shaped like little index cards E) none of the above
12) The remains of organisms preserved in sedimentary rocks that are accumulated in the same age sequence as the sediments that contain them can be used to determine age relationships. This is called A) original horizontality. B) superposition. C) fossil correlation. D) cross-cutting relationships. E) antecedence.
13) Geologic age given in specific units of time, such as millions of years, is known as A) relative dating. B) temporal dating. C) absolute dating. D) Dutch dating. E) automatic dating.
14) The principle of stratigraphy, one of the simplest methods of relative dating, states that A) all organisms die face down in the mud. B) the rocks on top of a layered sequence are older. C) sedimentary layering was initially horizontal. D) horizontal dikes are younger than vertical dikes. E) none of the above
15) The law or principle of superposition states that A) the rocks on top are older. B) the rocks on top are younger. C) sedimentary layering was initially horizontal. D) horizontal dikes are younger than vertical dikes. E) none of the above
16) The order of crystallization of several granite dikes can be determined from A) cross-cutting relationships. B) original horizontality. C) superposition. D) radiometric dating only. E) faunal succession (fossil correlation).
17) Which of these unconformities is defined by the presence of layered sedimentary rocks on igneous or metamorphic rocks? A) nonconformity B) disconformity C) angular unconformity D) confirmation E) irregularity
18) A vertical sequence of rock layers includes the following sequence from bottom to top: (1) sandstone with rare broken shells of shallow water marine organisms, (2) regularly layered gray shale, and (3) limestone with abundant fossilized coral. The best interpretation of this sequence is a(n) A) regression. B) change from glacial to fluvial environments. C) transgression. D) alluvial fan overlain by fluvial sediments. E) relative drop in sea level.
19) The era in which we live is known as the A) Age of Reason. B) Cenozoic. C) Mesozoic. D) Paleozoic. E) Precambrian.
20) The largest units of geologic time are A) eras. B) epochs. C) eons. D) periods. E) columns.
21) If a radioactive isotope has a half-life of one million years, and a rock contains a mixture of 25% parent and 75% daughter isotopes, the age of the rock is A) 5 million years. B) 1 million years. C) 750, 000 years. D) 2 million years. E) 250, 000 years.
22) Radioactive decay is __________ and operates at a __________ rate. A) linear; constant B) exponential; declining C) linear; increasing D) exponential; constant E) none of the above
23) Radioactive decay of an isotope of an element produces A) nuclear cavities. B) isotopes of another element. C) no effect whatsoever. D) seismic tremors. E) nothing but stable elements.
24) Which of the following decay schemes is incorrect? A) _elementsubscript_element --> _elementsubscript_element B) _elementsubscript_element --> _elementsubscript_element C) _elementsubscript_element --> _elementsubscript_element D) _elementsubscript_element --> _elementsubscript_element E) All of the above are incorrect.
25) Carbon-14 dating is used for dating A) geologically young materials (less than 50,000 years). B) charcoal. C) burnt pottery shards. D) volcanic eruptions in forests. E) all of the above
TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false.
26) The first scientific attempts to measure geologic time were made about 60 years ago.
27) Most estimates for the age of Earth before 1896 were less than a few million years.
28) You can use the simple equation of (time) = (sediment thickness)/(rate of accumulation) to calculate the age of a certain sedimentary formation.
29) Lord Kelvin estimated an age of Earth in the range of 20 to 30 million years based on the salinity of water in the oceans.
30) Relative dating is the application of simple rules of logic to determine the numerical age of a rock formation.
31) "Hutton's Unconformity" is a reference to the fact that James Hutton disagreed with just about all other geologists of his time regarding the age of Earth. 32) A sudden increase in ridge volume will result in global transgressions.
33) Fossils give the best control on the absolute age of the Earth.
34) An unconformity represents an immense gap in time. 35) An unconformity is a gap in the rock record.
36) The geologic time scale has four major divisions, called periods.
37) Meteorite impacts are the only explanation for mass extinctions on Earth. 38) Fossil correlation is not very useful for rocks older than about 540 million years.
39) The Phanerozoic Eon, which means "life present", includes the Cenozoic, Mesozoic, and Paleozoic eras.
40) Most rocks preserved on Earth date from the Archean eon.