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TOEFL Directory > TOEFL writing > TOEFL Reading Class Unit 2_Passage 12_Question 122-132
TOEFL Reading Class Unit 2_Passage 12_Question 122-132
You have about 15 minutes to finish this passage.
First,use about 3-4 minutes to read the passage, try to understand the main idea of this passage.
Don't read it so slowly or try to remember all details.You need to do "fast reading",and "scan" the passage.
Second, read questions 1-11, and with questions you go back the passage again and look for correct answers.
Question 122-132
Passge 12
Geologists can measure geologic time by tracing fossils through the rock strata, or layers, and by noticing the greater change in the deeper rocks as compared to those near the surface. Fossil-bearing strata can be followed horizontally over great distances, because a particular fossil bed can be identified even in another locality with respect to beds above and below it. These are called marker beds and are used for identifying geologic formations. They originally were used in the exploration for coal, one of the first practical uses of geology. Since coal-bearing seams are generally the same age and were laid down during times of abundant plant life, geologists could determine where to mine coal by studying the fossil content of rocks.
When fossils are arranged according to their age, they do not present a random or haphazard picture, but instead show progressive changes from simple to complex forms and reveal the development of species through time. Paleontologists are thus able to recognize geologic time periods based on groups of organisms that were especially abundant and characteristic during a particular time. Within each period, there are many subdivisions determined by the occurrence of certain species. This same succession is never out of order and is found on every major continent.
Both large and small extinctions of different groups of species were used by 19th century geologists to define the boundaries of the geologic timescale. But because there was no means of actually dating rocks, the entire geologic record was delineated using relative dating techniques, which only indicated which bed was older or younger according to its fossil content. Therefore, relative
dating only places rocks in their proper sequence or order and does not indicate how long ago an event took place, only that it followed one event and preceded another. Before the evelopment of radiometric dating techniques, geologists had no method of dating events precisely. Thus, relative dating techniques were developed and are still used today. Absolute dating methods such as adiocarbon dating, which was discovered in the late 1940's, did not replace these techniques, however, but only supplemented them.
122. What does the passage mainly discuss?
a) Fossil formation
b) Exploring for coal
c) Geologic age dating
d) Ancient plant life
123. The word tracing in the passage is closest in meaning to
a) marking
b) copying
c) following
d) interpreting
124. Individual fossil beds can be identified by
a) comparing them to the beds above and below them
b) locating coal seams in the rock
c) analyzing the chemical elements found in the rock
d) understanding the plant life presently found in the area
125.
126.
127.
128. The word another in the passage refers to
a) event
b) order
c) fossil content
d) development
129. What is a limitation of relative dating techniques?
a) The techniques are not very accurate.
b) Paleontologists and geologists disagree on when these techniques should be used.
c) Geologists prefer radiometric dating techniques to relative dating ones.
d) The techniques do not indicate exactly when an event occurred.
130. The paragraph following the passage most likely discusses
a) species that are now extinct
b) uses of relative dating techniques
c) field exploration methods used by geologists
d) uses of radiometric dating techniques
131.
132.
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