Relative+Dating+Activity+Sp21

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Geology

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Dec 6, 2023

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Plenge S21 Relative Dating Activity Your name Poojha Palle Group # 2 ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Use this diagram for the questions 1-4. Note that “B” and “E” are faults. Other layers are sedimentary. 1. Which answer choice correctly identifies a visible unconformity in this diagram? a. Contact between layers H and D b. Contact between layers C and A c. Contact between layers F and A d. Contact between layers F and H 2. Which layers or faults are OLDER than fault B? a. G, C, and A c. G, C, A, and F b. Layer F only d. All layers shown 3. Which answer choice correctly compares the ages of fault E and fault B? a. Fault B broke and shifted rocks before fault E b. Fault B broke and shifted rocks after fault E c. Fault B broke and shifted rocks as the same time as fault E did d. The order of events cannot be discerned from this information alone 4. List layers/faults in order from oldest to most recent: G, C, A, F, B, H, D, I, E. ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Use this diagram for 5-8. “F” & “L” are igneous intrusions; “G” is a fault. 5. Which is older: a. Intrusion F b. Fault G 6. Where in this picture would metamorphic rocks be found? a. Where H & I meet b. Where F & (A, B, C, & D) meet c. Where H & (C, D, & E) meet 7. Layer “C” is shale (which often forms in deep marine environments) layer “D” is limestone (often forms in shallow marine environments) and layer “E” is sandstone (often formed in coastal environments). Which choice best describes how this area changed while these layers were being deposited? a. Sea level was rising over that period of time b. Sea level was falling over that period of time 8. Intrusion F has been radiometrically dated and is around 750 million years old. What does this tell you about the when the deep ocean that produced layer “C” existed? a. A deep ocean existed here MUCH earlier than 750 million years ago b. A deep ocean existed here approximately 750 million years ago c. A deep ocean existed here MUCH later than 750 million years ago
9. Earth has sedimentary bedrock of marine (oceanic) origin that is 4 billion years old. What inference can be made based on this information? a. Earth has oceans four billion years ago b. Sedimentary rocks formed from magma when Earth cooled 4 billion years ago c. Most sedimentary rocks are at least 4 billion years old d. Life existed on Earth 4 billion years ago ---------------------------------------------------------------------------------------------------------------------------------------------------------------- 10. This diagram represents three bedrock outcrops. The layers have NOT been overturned. Letters A through E identify different rock layers. Fossils found in the rock layers are shown. Which fossil could be classified as an index fossil useful in correlating the rock layers? (circle one) ---------------------------------------------------------------------------------------------------------------------------------------------------------------- 11. Short answer. The diagram below represents three bedrock outcrops, found several kilometers apart. The geologic time period when each sedimentary rock layer formed is shown. The symbols represent fossils of different types of organisms. a. Which fossil symbol represents the best index fossil? Describe one piece of evidence shown in the outcrops that indicates that this fossil has characteristics of a good index fossil. The best index fossil would be the circle because it appears consistently in the Devonian period and, therefore, how old the exposed rocks are per outcrop. Not to mention, it doesn’t appear in any other time period. b. Explain why the geologic age of these rock layers could NOT be accurately dated using C-14. C-14 has a relatively lower half-life of around 5,000 years. The Permian period, the youngest period, is still around 250 million years old. Carbon-14’s parent isotopes wouldn’t exist anymore (or would exist in infinitesimally small percentages) way before this period could be dated. ---------------------------------------------------------------------------------------------------------------------------------------------------------------- 12. Why is paleomagnetism (the preservation of Earth’s magnetic field in rocks) considered a relative dating technique rather than an absolute dating technique? This is because we can only give a range of years in which the magnetic field was oriented a certain way. This range of years and its corresponding polarity of the Earth can be compared to the magnetic record of rocks, but cannot give absolute values.
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