Geologic History. 1. Identify the letter of the rock unit that was formed at the same time as igneous rock unit H.

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1 Geologic History Name Base your answers to questions 1 through 3 on the geologic cross section in your answer booklet. Rock units A through H are shown. Several rock units contain fossils. Rock unit G was formed in a zone of contact metamorphism. 1. Identify the letter of the rock unit that was formed at the same time as igneous rock unit H. 2. Identify two possible geologic periods during which the sediments that formed rock unit E could have been deposited. 3. Explain why the absolute age of the fossils shown in the cross section can not be determined by using radioactive carbon The graph below shows the extinction rate of organisms on Earth during the last 600 million years. Letters A through D represent mass extinctions. Which letter indicates when dinosaurs became extinct? A) A B) B C) C D) D 5. The characteristic of the radioactive isotope uranium-238 that makes this isotope useful for accurately dating the age of a rock is the isotope s A) organic origin B) constant half-life C) common occurrence in sediments D) resistance to weathering and erosion

2 6. The table below shows how the radioactive decay of potassium-40 can be used to determine the age of a rock. How old is a sample of granite that contains 8 grams of radioactive potassium-40 and 56 grams of its nonradioactive decay products? A) B) C) D) Base your answer to the following question on the geologic cross section below of a region of Earth's crust. Rock layers A through E have been labeled. Two index fossils are shown and their locations within the rock layers are indicated. Evidence of tectonic activity in this cross section is provided by the A) folding and tilting of the rock layers B) faulting and movement of the rock layers C) igneous intrusion into the rock layers D) collision of crustal plate boundaries in the rock layers

3 8. The diagram below shows an index fossil found in surface bedrock in some parts of New York State. In which New York State landscape region is this gastropod fossil most likely found in the surface bedrock? A) Tug Hill Plateau B) Allegheny Plateau C) Adirondack Mountains D) Newark Lowlands 9. Base your answer to the following question on Base your answers to questions 26 and 27 on the diagram below, which shows specific events in the history of Earth from the beginning of the universe to the present. During which geologic era did life first appear on land? A) Middle Archean B) Paleozoic C) Middle Proterozoic D) Cenozoic

4 10. Base your answer to the following question on the cross sections below, which show widely separated outcrops labeled I, II, and III. Index fossils are found in some of the rock layers in the three outcrops. In outcrop III, layers A, B, C, and D are labeled. Line XY represents an unconformity. Line GH represents a fault. On outcrop II below, place the symbol ~~ for an unconformity between the two rock layers where the Silurian-age bedrock has been removed by erosion. 11. At which latitude and longitude in New York State would a salt mine in Silurian-age bedrock most likely be located? A) 41 N 72 W B) 43 N 77 W C) 44 N 74 W D) 44 N 76 W 12. Samples of plant pollen are preserved in sediment deposited by the last glacial ice sheet. Which radioactive isotope is best for determining the age of the samples? A) potassium-40 B) carbon-14 C) uranium-238 D) rubidium The largest meteorite impact crater in North America formed approximately 1,850 million years ago, which was during the A) Middle Archean Era B) Early Proterozoic Era C) Early Jurassic Period D) Late Cretaceous Period 14. If a sample of a radioactive substance is crushed the half-life of the substance will A) decrease B) increase C) remain the same

5 15. Base your answer to the following question on the diagram below, which represents a model of a radioactive sample with a half-life of 5000 years. The white boxes represent undecayed radioactive material and the shaded boxes represent the decayed material after the first half-life. Which radioactive isotope has a half-life closest in duration to this radioactive sample? A) carbon-14 B) potassium-40 C) uranium-238 D) rubidium The geologic cross section below shows an unconformity in New York State bedrock layers that have not been overturned. Index fossils found throughout some rock layers are shown. Which New York State index fossil may have been present in a rock layer that is missing due to the unconformity? A) B) C) D)

6 17. An ancient bone was analyzed and found to contain carbon-14 that had decayed for nearly two half-lives. Approximately how old is the bone? A) 1,400 years B) 2,800 years C) 5,600 years D) 11,000 years 18. The block diagram below of a portion of Earth's crust shows four zones labeled A, B, C, and D outlined with dashed lines. In which zone is a younger rock unit on top of an older rock unit? A) A B) B C) C D) D 19. Base your answer to the following question on the geologic cross section below of the Grand Canyon. The numbers 1 through 10 represent Paleozoic sedimentary rock layers. Which Paleozoic rock layer is the oldest? A) 1 B) 10 C) 5 D) 4

7 20. During which period of geologic history was the surface bedrock of the Catskills deposited? A) Cambrian B) Pleistocene C) Devonian D) Triassic 21. The diagram below represents the skull of a saber-toothed tiger that died 30,000 years ago. The age of the skull could be determined most accurately by using A) uranium-238 B) rubidium-87 C) potassium-40 D) carbon-14

8 22. Base your answer to the following question on the geologic cross section of bedrock shown below. A through G identify rock layers and Q represents a fault. Lines W, X, Y, and Z are locations of unconformities. The rocks have not been overturned. Which rock most likely formed in the zone of contact between rock E and rock F? A) obsidian B) slate C) metaconglomerate D) sandstone 23. Which New York State landscape region could have surface bedrock containing dinosaur fossils? A) Adirondack Highlands B) Erie-Ontario Lowlands C) St. Lawrence Lowlands D) Newark Lowlands 24. During which geologic period would fossils in the exposed bedrock of New York State at 43º N, 77º W most likely have been deposited? A) Cambrian B) Ordovician C) Silurian D) Devonian

9 25. Studies of the fossil record found in Utah indicate that A) variations within a species can be observed, measured, and described B) variations within a species have had little effect upon the survival of the species C) few of the species of plants and animals that existed have become extinct D) there is no evidence for evolutionary development among the different fossil species 26. The cross section below shows undisturbed sedimentary bedrock. The ages of various layers are indicated, and reference points within the rocks are labeled A through D. The remains of an early dinosaur could be found at reference point A) A B) B C) C D) D

10 27. Base your answer to the following question on the cross sections below, which show widely separated outcrops at locations X, Y, and Z. At location Y, the boundary between the red sandstone and the black shale marks the A) beginning of the Cenozoic Era B) beginning of the Mesozoic Era C) end of the Cenozoic Era D) end of the Mesozoic Era 28. Which column best represents the relative duration of the major intervals of geologic history? A) B) C) D)

11 29. The geologic cross section below shows sedimentary rock layers A, B, C, and D, which have not been overturned. E is an igneous intrusion. Line XY represents a fault. Which geologic event occurred most recently? A) deposition of sediments for rock layer A B) formation of the fault C) intrusion of the igneous material E D) cementation of sediments for rock layer D 30. Base your answer to the following question on the geologic cross section below. The cross section shows an outcrop in which the layers have not been overturned. Rock units are labeled A through E. State the name of the sediment that was compacted to form rock unit A.

12 31. Base your answer to the following question on the diagram, which shows the evolutionary development of the horse, as supported by the fossil record. Which statement best explains the changing appearance of the horse, as supported by the fossil record? A) The horse evolved due to the influence of humans. B) The horse evolved from a complex life-form to a simpler life-form. C) The horse evolved into a life-form better able to survive. D) The horse evolved from larger ancestors without forelimbs. 32. The diagram below shows a geologic cross section of a portion of a landscape region. What is the probable geologic age of sedimentary rock unit X? A) Cambrian B) Precambrian C) Permian D) Silurian

13 Base your answers to questions 33 and 34 on the graph below which shows the decay rates of four radioactive substances, A, B, C, and D. 33. When 90 percent of the original mass of isotope D remains, what total percent of the original mass of isotope B remains? A) 10% B) 22% C) 63% D) 90% 34. The half-life of these radioactive substances depends on the A) pressure acting on the material B) amount of the material C) temperature of the material D) composition of the material 35. Earth scientists studied fossils of a certain type of plant. They noted slight differences in the plant throughout geologic time. What inference is best made from this evidence? A) When the environment changed, this type of plant also changed, allowing it to survive. B) When uplifting occurred, the fossils of this type of plant were deformed. C) The processes which form fossils today differ from those of the past. D) The fossils have changed as a result of weathering and erosion.

14 36. Base your answer to the following question on the graph below which shows the rate of radioactive decay of element A and the rate at which decay product B is formed. If the half-life of radioactive element A is 10,000 years, for which time interval would this element be most useful in determining the age of rock? A) Precambrian B) Devonian C) Mississippian D) Pleistocene 37. Base your answer to the following question on the diagram below which represents a cross section of an eroded fold that has not been overturned. If rock layer A is of Devonian Age, rock layer E could be of A) Triassic Age B) Carboniferous Age C) Cambrian Age D) Tertiary Age 38. A rock sample containing the radioactive isotope potassium-40 is calculated to be years old. How much of the original potassium-40 would be left in this rock sample? A) 0 B) 1/8 C) 1/4 D) 1/2 39. Which conclusion can be made based on existing fossil evidence? A) Present life forms have always existed. B) The Earth's environment has always been the same. C) Many life forms have become extinct. D) All life forms will remain the same in the future.

15 40. Base your answer to the following question on the diagrams below, which represent two bedrock outcrops, I and II, found several kilometers apart in New York State. Rock layers are lettered A through F. Drawings represent specific index fossils. Explain why carbon-14 can not be used to find the geologic age of these index fossils. 41. When did armored fishes become extinct? A) before the appearance of dinosaurs B) before the appearance of terrestrial plants C) after the appearance of reptiles D) after the appearance of birds

16 42. Base your answer to the following question on the date table below, which shows the radioactive decay of carbon-14. The number of years required to complete four half-lives has been left blank. How long does it take for radioactive carbon-14 to complete four half-lives? 43. Base your answer to the following question on the paragraph below, which provides background information regarding recent fossil discoveries in Canada. Scientific evidence indicates that the earliest mammals may have evolved approximately 225 million years ago from an ancient reptile group called the therapsids. For millions of years afterward, early mammals and therapsids coexisted until the therapsids apparently became extinct 165 million years ago. However, geologists have recently found a fossil they believe to be a therapsid that is only 60 million years old. They found the fossil, which they have named Chronoperates paradoxus (paradoxical time-wanderer), near Calgary in Canada. This find suggests that for 105 million years after the apparent extinction of the therapsids, a few of the reptiles continued to live in a narrow geographic range in Canada. According to fossil evidence, during which geologic period did the earliest mammals appear on Earth?

17 Base your answers to questions 44 and 45 on the diagram and information below about fossil snails. Snails have lived in most of the world's oceans over a period of hundreds of millions of years. Paleontologists discovered that in warm, tropical waters more snails have shells that, when viewed from the top, spiral outward in a clockwise direction. In cool or cold waters, more snails have shells that spiral outward in a counterclockwise direction. Both clockwise- and counterclockwise-spiraled snail fossils have been found in New York State bedrock. 44. In a slab of rock that contains many fossil snails, what evidence would lead geologists to conclude that the slab was formed in a tropical climate? 45. State one reason bedrock that formed in tropical regions is found in New York State.

18 Answer Key Geologic History Regents Review 1. G 2. Devonian Period or Mississippian Period Carboniferous Period or Devonian Period 3. The fossils are too old for 14 C dating. Carbon-14 has a very short half-life. 4. D 5. B 6. C 7. A 8. A 9. B B 12. B 13. B 14. C 15. A 16. B 17. D 18. A 19. A 20. C 21. D 22. C 23. D 24. C 25. A 26. A 27. B 28. A 29. C 30. clay 31. C 32. D 33. B 34. D 35. A 36. D 37. C 38. B 39. C 40. Examples: Carbon-14 s half-life is too short. Not enough carbon-14 is left to measure. The fossils are too old. 41. A ,800 yr. 43. Triassic Period. 44. Example: Clockwise spiral snail shells are found in greater numbers. 45. Examples: New York State experienced a warmer climate when it was located closer to the Equator. The North American Plate has drifted northward from the equator region over time.