2. How did earth s early atmosphere form? What gases were present? 5. Explain why igneous and metamorphic rocks cannot contain fossils.

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1 Name: Review topics: Earth s History Date: I. The History of the Earth 1. Describe how the earth began. 2. How did earth s early atmosphere form? What gases were present? 3. How was oxygen produced? When did oxygen first start to appear? 4. What is the geologic time scale based on? 5. Explain why igneous and metamorphic rocks cannot contain fossils. 6. Why is the fossil record incomplete (think: why do we have few to no fossils from the Precambrian Eon?) II. Relative Age Dating 7. Define relative age dating. 8. Define uniformitarianism. 9. What does the principle of superposition tells us about rock layers? 1

2 10. What is contact metamorphism? What does it say about the age relationship between an igneous intrusion and the surrounding rock? 11. What is an unconformity? How does it form? III. Absolute Age 12. Define absolute age dating. 13. What is the difference between a parent element and a daughter element? 14. What is a half-life? 15. Which radioactive element is usually used to date recent fossils? 16. What percentage of the parent element of a radioactive substance is left after two half-lives? IV. Correlation 17. Define correlation. 2

3 18. What are the four ways we can correlate rocks or geologic events? 19. Name two conditions that classify an organism as an index fossil. V. Geologic Time Scale 20. What is the largest era of geologic time? Why is much of this era condensed (shortened) in the Earth Science Reference Tables? 21. When did the Devonian period begin? 22. During which geologic period did Eospirifer exist? 23. What animals appeared during the Triassic period? 24. How many geologic periods did the ammonoid group live? 25. What geologic period did the dome-like uplift of the Adirondack Mountains begin? 26. What landscape region would be able to find Elliptocephala? 3

4 Event Sequencing. Using the event list and the picture below, determine the order of events from oldest to youngest. F youngest oldest Event:

5 Geologic Events Practice Questions Base your answers to questions 1 through 3 on the geologic cross section below in which overturning has not occurred. Letters A through H represent rock layers. 1. Which sequence of events most likely caused the unconformity at the bottom of rock layer B? (1) folding uplift erosion deposition (2) intrusion erosion folding uplift (3) erosion folding deposition intrusion (4) deposition uplift erosion folding 2. The folding of rock layers G through C was most 3. Which two letters represent bedrock of the likely caused by same age? (1) erosion of overlying sediments (1) A and E (2) contact metamorphism (2) B and D (3) the collision of lithospheric plates (3) F and G (4) the extrusion of igneous rock (4) D and H 4. In a certain section of sedimentary rock, fossil dating shows that younger rock layers are on top of older layers. This relationship indicates that: (1) the rock layers were formed according to the law of superposition (2) the rock layers were overturned (3) fossil dating is inaccurate (4) the sediments that formed the rock layers were composed of many different minerals 5. An unconformity between two sedimentary layers is most likely produced by (1) uplift followed by extensive erosion, subsidence, and deposition (2) a period of extrusive volcanism followed by another period of extrusive volcanism (3) continuous sedimentation in a deep basin over a long period (4) the deposition of gravel followed by the deposition of sand and silt 6. The diagram below represents an exposed rock outcrop. Which geologic event occurred last? (1) intrusion of A (2) the fault along B (3) the deposition of gravel at D (4) the fold at C 7. Unless a series of rock layers has been overturned, the bottom rock layer usually (1) is the oldest (2) contains the greatest variety of minerals (3) contains fossils (4) has the finest texture 5

6 Based your answers to questions 8 through 12 on the diagram below. The diagram represents a geologic cross section in which no overturning has occurred. 8. Which feature is represented by line WX? (1) a former erosional surface (2) a fault (3) an area of metamorphism (4) an igneous intrusion 9. When did the folding of rock layer B most likely occur? (1) after the deposition of rock layer D (2) before the deposition of rock layer A (3) after the deposition of rock layer C (4) after the deposition of rock layer E 10. Fossils are least likely to be found in which rock? (1) E (2) C (3) F (4) D 11. What rock layer is probably the oldest? (1) D (2) B (3) F (4) A 12. What evidence in the rock layers that the formation of igneous rock F occurred after rock layer E was in place? (1) The zone of contact metamorphism between rock F and rock E (2) The unconformity between rock F and rock layer E (3) The presence of extrusive igneous rock below layer E (4) The presence of radioactive minerals in rock layer F 6

7 Absolute Age/Radioactive Decay Questions 1. 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 1. organic origin 3. common occurrence in sediments 2. constant half-life 4. resistance to weathering and erosion 2. The accompanying graph shows the rate of decay of the radioactive isotope K-40 into the decay products Ar-40 and Ca-40. Analysis of a basalt rock sample shows that 25% of its radioactive K-40 remained undecayed. How old is the basalt? billion years billion years billion years billion years 3. Base your answer on the accompanying diagram, 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. How many more boxes should be shaded to represent the additional decayed material formed during the second half-life?

8 4. The table shown gives information about the radioactive decay of carbon-14. Part of the table has been deliberately left blank for student use. After how many years will 1/128 gram of the original carbon-14 remain? 1. 22,800 yr 3. 34,200 yr 2. 28,500 yr 4. 39,900 yr 5. The diagram shown represents the present number of decayed and undecayed atoms in a sample that was originally 100% radioactive material. If the half-life of the radioactive material is 1,000 years, what is the age of the sample represented by the diagram? 1. 1,000 yr 3. 3,000 yr 2. 2,000 yr 4. 4,000 yr 6. Which radioactive isotope is most useful for determining the age of mastodont bones found in late Pleistocene sediments? 1. uranium potassium carbon rubidium-87 8