Laboratory 7_1 Geologic Time

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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 1/49 Laboratory 7: Geologic Time Due May 29 at 11:59pm Points 14 Questions 26 Available May 20 at 9am - May 29 at 11:59pm 10 days Time Limit None Allowed Attempts 2 Instructions Attempt History Attempt Time Score KEPT Attempt 2 29 minutes 12.06 out of 14 Learning Goals By completing this lab, students will: Appreciate the near-eternity of geologic time. Learn and apply relative dating techniques. Understand how numerical dating methods work and how to interpret the data. Apply geologic time concepts on a geologic map of Washington state. ESS101 Lab 7: Geologic time ESS101 Lab 7: Geologic time You are allowed 2 attempts to complete this lab. A link to the PDF version of Lab 7 is provided here: Lab 7 PDF
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 2/49 Attempt Time Score LATEST Attempt 2 29 minutes 12.06 out of 14 Attempt 1 2,570 minutes 12.06 out of 14 Score for this attempt: 12.06 out of 14 Submitted May 29 at 9:36pm This attempt took 29 minutes. Geologic processes have been active on earth since its formation 4.54 billion (4,540,000,000) years ago. Unfortunately, evidence of early Earth is hard to come by, as older crust has been weathered and eroded away or recycled back into the mantle through subduction processes. However, we are still able to glean details about the Earth’s history from the geologic record . Specifically, the characteristics of the rocks that still remain on the Earth’s surface can give us clues and insights into the Earth’s past. Figure 7-1 Clock analogy showing earth history compressed into one hour . It is hard to think about geologic timescales without understanding the vastness of geologic time. While we can directly observe some geologic processes (e.g. a volcanic eruption, an earthquake, some weathering processes), most are too slow to be observed during human lifetimes. Furthermore, even the sheer amount of time that human beings 1
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 3/49 have existed on Earth is dwarfed by the timescales of many geologic processes (Figure 7-1). Geologists use a geologic time scale to place geologic events in chronological order. Rock samples can be dated and placed within the geologic time scale using relative and/or numerical dating techniques. Relative dating techniques establish the age of a rock relative to other rock samples, while absolute dating techniques can be used to assign a more precise numerical age to a rock. http://www.extinctblog.org/extinct/2017/10/23/stop-the-clocks-and- the-other-geologic-timescale-metaphors-too (http://www.extinctblog.org/extinct/2017/10/23/stop-the-clocks-and-the-other- geologic-timescale-metaphors-too) 1 0.25 / 0.25 pts Question 1 Laboratory Honor Statement Cheating or plagiarism of any kind will not be tolerated in ESS 101. This includes copying answers from a friend or classmate, copying answers verbatim found on the internet or other literary sources, or copying any work that may answer the question being asked. Make sure you always use your own words when answering the questions in the homework and cite appropriate references if you use them to help you answer the question. Anyone caught violating the academic code of conduct (https://www.washington.edu/cssc/for-students/academic-misconduct/) will receive a “0” grade on the assignment, and if the conduct is deemed egregious, reported to the UW Academic Misconduct representative. I acknowledge that I have carefully read and understand the above statement regarding the consequences of cheating and plagiarism, and promise to complete my work in this class with honesty and integrity. Answer "True" below supporting your acknowledgement. True Correct! Correct! False
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 4/49 1 / 1 pts Question 2 Answer 1: Answer 2: (a) The first fossils of animals with hard parts appeared about 541 million years ago. What percentage of geologic time does the fossil record represent? Express your answer as a percentage with two significant figures. 12 % (b) Modern humans (Homo sapiens sapiens) appeared about 300,000 (0.3 million) years ago (Mounier and Lahr, 2019). For what percentage of earth’s history has earth been occupied by modern humans? Express your answer as a percentage with two significant figures. 0.0066 % (c) The dimensions of space are somewhat analogous to the dimension of time. Consider a human hair to conceptualize the length of earth history. The average strand of human hair is 0.1mm in width. If the width of one human hair strand represents the duration of human occupation of earth (300,000 years), how wide would a hair strand be that represented the duration of the earth’s history (4.54 billion years)? Express your answer in meters using two significant figures. **Hint: Divide 0.1 mm by the percentage you found in the previous question. This is the answer in mm. 1m = 1000 mm** 1.5 meters 12 Correct! Correct! 0.0066 Correct! Correct! .0066 orrect Answer orrect Answer .0065 orrect Answer orrect Answer 0.0065 orrect Answer orrect Answer
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 5/49 Answer 3: 1.5 Correct! Correct! 0.25 / 0.25 pts Question 3 Research into geologic history depends on geological observations (like rock samples where we can measure physical or chemical properties). If you were a geological researcher trying to study the oldest crust on earth, where would you expect to find rock samples to support your work? On the ocean floor because that is where new crust forms. On the ocean floor because it has the lowest elevation. On a continental plate because continents are not easily subducted. Correct! Correct! On a continental plate because they have the steepest slopes.
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 6/49 Figure 7-2: Geologic Time Scale. (Ka = Kilo-annum = thousands of years, Ma = Mega-annum millions of years, Ga = Giga-annum = billions of years) Geologists (and many other scientists who study the past) use the geologic time scale to describe different periods of earth’s history. The geologic time scale divides earth’s history into a series of chronologic subdivisions that are defined by important geologic events, such as the oxygenation of earth’s atmosphere or the evolution of different species. The names and descriptions of each type of subdivision are listed below and are included as headings in figure 7-2. Eon: eons are defined by important planetary developments in earth’s history, like the development of multicellular life. Era : each era describes a length of time with different dominant lifeforms Period : periods are defined by evolutionary changes in the fossil record Epoch: epochs are differentiated by other detectable changes in the geologic record
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 7/49 0.25 / 0.25 pts Question 4 Answer 1: Answer 2: Answer 3: We are currently living in the Quaternary period. Identify the eon, era, and epoch that you have, in part, witnessed during your lifetime: EON : Phanerozoic ERA : Cenozoic EPOCH : Holocene Phanerozoic Correct! Correct! Cenozoic Correct! Correct! Holocene Correct! Correct! 0.25 / 0.25 pts Question 5 Answer 1: In which eon would you expect most of the rocks at earth’s surface to have formed? Phanerozoic Phanerozoic Correct! Correct! 0.33 / 0.5 pts Question 6
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 8/49 The distinction between eons is based on very broad planetary developments, like the formation of an oxygenated atmosphere or the emergence of multicellular life. For example, the Phanerozoic eon reflects all time in earth’s history since the appearance of shells in the fossil record. Other subdivisions of the geologic time scale (including eras, periods, and eons) require more specific observations based on the existence of specific species or geochemical conditions. Why are there no subdivisions for the Hadean, Archean, or Proterozoic eons? (Select all that apply) Rocks on earth are continually created and destroyed, which means most rocks formed during these eons no longer exist Correct! Correct! Life on earth was not abundant prior to the Phanerzoic Eon orrect Answer orrect Answer Because they are so old, we are more uncertain about the age of rocks from these eons Correct! Correct! 1. Determining Relative Ages Relative dating techniques use physical and/or chemical observations about a rock to provide an age that is relative to another rock or process age. These observations allow us to say one rock is older than another, but they do not tell us exactly when the rock formed. For example, when we looked at clastic sedimentary rocks, we knew that the clasts were older than the cement that held them together. These same principles apply to very large-scale geologic formations. 0.5 / 0.5 pts Question 7
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 9/49 During the Proterozoic era, earth’s atmosphere evolved alongside cyanobacteria on earth’s surface. Imbalances in the production and uptake of free oxygen led to fluctuations in the atmospheric and oceanic oxygen content. For about 800,000,000 years, this imbalance caused alternating deposits of iron oxides (black bands) and iron-rich silica (red bands) on the ocean floor, creating a banded iron formation. Which of the following could be said of this formation pictured above? This rock formation is older than the Phanerozoic because it couldn’t have formed in a fully oxygenated environment. This rock is younger than the Hadean because it formed in the oceans, which are thought to have formed at the onset of the Archean. With the information provided, it is only possible to assign this formation a relative age. All of the answers are correct. Correct! Correct!
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 10/49 Stratigraphic Principles The way in which rocks are layered or positioned can tell us a lot about the relative ages of different rock units. There are several principles, first proposed by Nicholas Steno in 1669, that help us date geologic rock units in a relative sense. These principles are necessary to unravel the history of the earth that is contained in the geologic record and are used every day by geoscientists. (1) The Principle of Original Horizontality says that the layers of sedimentary and volcanic rock are generally deposited as horizontal layers (Figure 7-3). There are exceptions to the rule, such as rock deposited on the sides of mountains, but such rocks are unlikely to be preserved in the geologic record compared to flat-lying layers deposited in broad basins. Foreset beds of a delta are also deposited as non-horizontal layers. If rocks are not found in horizontal layers, it is usually because subsequent geologic processes have tilted or folded those strata (layers). This law applies to all rocks that form at earth’s surface, such as sedimentary rocks and many volcanic rocks. For example, sediment is originally deposited in horizontal layers within a depositional basin and subsequently lithified into sedimentary rock. Figure 7-3 : The Principle of Original Horizontality. (2) The Principle of Superposition is based on the observation that each individual layer at the surface is deposited on top of the previous layer. Therefore, unless the layers have been overturned
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 11/49 by later geologic processes, the oldest layers are at the bottom and the youngest layers are at the top (Figure 7-4). Figure 7-4 : The Principle of Superposition. (3) The Principle of Cross-Cutting Relations states that a feature cutting across another feature is younger than the object it is cutting. For example, a crack in a concrete sidewalk is younger than the concrete sidewalk. In a geologic context faults and igneous intrusions (plutons) are younger than the pre-existing rock they cross-cut or intrude (Figure 7-5). Figure 7-5 : The Principle of Cross-Cutting Relations. (4) The Principle of Inclusion states that sedimentary clasts are older than the strata that contain them. For example, the pebble- sized clasts in a conglomerate (Figure 7-6) formed before the conglomerate itself, or sand grains in a sandstone predate the sandstone rock.
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 12/49 Figure 7-6 : The Principle of Inclusion. If clast A is dated at 55 million years old, clast B is dated at 75 million years old, and clast C is dated at 110 million years old, what can you infer about the age of the formation of the conglomerate related to the three numerical ages for the included clasts? Remember from lecture… the conglomerate must be younger than 55 million years old (or the youngest included clast)! The principle of inclusions also applies to xenoliths , which are “included bodies” incorporated into an igneous pluton during magma emplacement into the country rock (Figure 7-7).
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 13/49 Figure 7-7 Example of a xenolith found within an igneous rock. Think about chocolate chip cookies! Which is older, the chocolate chips, or the cookie? Which is older, the xenoliths, or the plutonic rock? The above granodiorite till boulder was deposited by the Puget Lobe ice sheet 15,000 - 18,000 years ago. It was eroded out of the glacial till in the upper bluff slope by wave processes, and deposited on the shoreline by recent landslide activity. (5) The Principle of Faunal Succession states that different sedimentary strata contain particular fossil assemblages by which the rocks can be identified and correlated over horizontal distances. The fossil assemblages (which may include animals and plants) succeed one another in defined habitual order (e.g., Figure 7-8). The principle was first recognized in the early 19th century by William Smith, an English geologist who was mapping sedimentary rocks. Smith recognized that certain rock layers in England contained specific fossil types and that the oldest rock units, contained more primitive life forms.
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 14/49 Figure 7-7 : The Principle of Faunal Succession. 0.5 / 0.5 pts Question 8 When rock layers are warped upwards, they can create a 3-dimensional dome. As the top of this dome is weathered and eroded away, concentric circles representing the different rock layers are revealed. Pictured below on the left is the Richat Structure, an exposed dome in the Sahara desert that is 40 km wide. In the dome schematic pictured below on the right, what can we conclude about the layers in the dome? Select all answers that apply. Layer A is older than layer B. Correct! Correct! Layer B is older than layer A.
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 15/49 Layers get older as we travel from the outer rim of the dome towards the center of the dome. Correct! Correct! The layers get younger as we travel from the outer rim of the dome towards the center of the dome. 1 / 1 pts Question 9 Answer 1: [Photo credit: John Howell] Use the image above to answer the following questions regarding stratigraphic principles. Using the law of cross-cutting relations, what can you conclude about the relative age of the sedimentary rock? The clastic sedimentary beds are older than the igneous dike. Using the law of superposition, what can you conclude about the relative ages of the sedimentary rock layers? The layers at the bottom of the photo are older than the layers at the top of the photo. Using the principle of inclusion, what can you conclude about the clasts in the sedimentary rock? The sedimentary rock formation is younger than the clasts.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 16/49 Answer 2: Answer 3: older than Correct! Correct! older than Correct! Correct! younger than Correct! Correct! 0.5 / 0.5 pts Question 10 [Photo credit: science.marshall.edu] Applying the law of cross-cutting relations to the rock pictured above, what is the order (first to last) in which the rock units A-D formed? Note that all of the dark-colored rock should be considered part of unit D. A, B, C, D
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 17/49 A, C, B, D D, C, B, A D, A, C, B Correct! Correct! B, C, A, D B, D, C, A 0.5 / 0.5 pts Question 11 [Photo credit: www.cokesmithphototravel.com (http://www.cokesmithphototravel.com) ] The photo above shows exposed sandstone strata on the Olympic Peninsula in Washington State. Select all of the following statements that are true. Layer A is the oldest marked layer
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 18/49 Layer B is the youngest marked layer Layer C is the oldest marked layer Regional pressures have deformed or tilted this rock formation Correct! Correct! We know that Layer B is between the ages of Layers A and C, but cannot say whether Layer A or Layer C is oldest from the information provided. Correct! Correct! Biostratigraphy Individual layers of sedimentary formations can include even more detail about the relative age of the strata if they include fossilized organisms. Since the types of organisms found on earth have changed over time, the existence of specific fossilized species in a layer can be used to correlate sedimentary formations worldwide. Certain plants or animals lived only for a brief period of geologic time, so their fossils can be used as an index or guide to that time. These fossils are called index fossils and are shown in Figure 7-9. Figure 7-10 shows the periods of geologic time in which those fossils can be found.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 19/49 Figure 7-9 Representative sketches of the main groups of invertebrates found in fossils. Figure 7-10 Generalized range of time periods over which index fossil species were alive. The width of each line identifies the relative abundance of that species.
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 20/49 0.25 / 0.25 pts Question 12 While on a hike, you find a sedimentary deposit that has been exposed near a beach. You are excited to use your ESS101 relative rock dating skills, so you quickly look for exposed fossils in the sedimentary layers. Unfortunately, you don’t find any. Which of the following must be true? The rock has to be from the Archean because it does not contain fossils The rock must have originally formed on the continent since there are no sea creatures There is not enough information to say; it is possible that there are fossils in the formation that you did not find or perhaps this formation does not contain fossils. Correct! Correct! 0.5 / 0.5 pts Question 13 You continue your search for fossilized materials in another nearby sedimentary rock sequence. You break apart a promising layer of mudstone to find the fossils (Sample A) shown below:
2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 21/49 Answer 1: Answer 2: Answer 3: What is the name of this index fossil group? trilobite Use Figure 7-10 to complete the following statement. This layer must be older than or from the Permian period and younger than or from the Cambrian period. trilobite Correct! Correct! Permian Correct! Correct! Cambrian Correct! Correct! 0.6 / 1 pts Question 14 Upon closer inspection, you find fossil samples B and C in the same stratigraphic unit as sample A.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 22/49 [Photo credit: Terry Swanson] What invertebrate index fossil group does sample B belong to? brachiopod What invertebrate index fossil group does sample C belong to? nautiloid Before leaving, you find even more fossils in the same layer, pictured below. [Photo credit: fossilera.com] What is the name of this index fossil group? belemnoid
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 23/49 Answer 1: Answer 2: Answer 3: Answer 4: Answer 5: Use figure 7-4 to complete the following statement. This layer must be older than or from the Cenozoic period and younger than or from the Mississippian period (Hint: think about the presence of all of the fossil assemblages found in this rock layer, including the previous question). brachiopod Correct! Correct! nautiloid Correct! Correct! belemnoid Correct! Correct! Cenozoic ou Answered ou Answered Permian orrect Answer orrect Answer Pennsylvanian orrect Answer orrect Answer Mississippian ou Answered ou Answered Stratigraphic Interpretations When rocks erode, a part of the geologic record is lost and the geologic time that was represented by the eroded rocks is erased. These gaps in the geologic record are called unconformities , and they can be caused by erosion or long periods of non-deposition. Unconformities exist anywhere that adjacent layers do not represent a continuous timescale.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 24/49 There are three basic kinds of unconformities that are shown in Figure 7- 11 and described below: Angular unconformity : stratified layers are deposited but then deformed/tilted. The top of the surface erodes, then more stratified layers are deposited. Disconformity : stratified layers are deposited, but some erode; more stratified layers are then deposited parallel to the eroded surface. Nonconformity : stratified layers are deposited on top of non-stratified igneous or metamorphic rocks that have been uplifted. You may also find the video below helpful for understanding how these missing layers occur. Unconformities: Finding Missing Time Unconformities: Finding Missing Time
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 25/49 Figure 7-11 Diagrams outlining the different types of unconformities and how they form. The final unconformity surface is outlined in red . [Source: https://openpress.usask.ca/geolmanual/chapter/overview-of-relative-and- absolute-dating/ (https://openpress.usask.ca/geolmanual/chapter/overview-of- relative-and-absolute-dating/) ]
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 26/49 Figure 7-12: Sequence of events leading to the development of an angular unconformity. [Image source: https://www.pinterest.com/pin/385480049329216033/ (https://www.pinterest.com/pin/385480049329216033/) ] 0.5 / 0.5 pts Question 15
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 27/49 [Photo credit: www.geologyin.com] The rock pictured above was cut into to make way for a road in Ecuador. Which of the following statement(s) are true for this formation? The strata are shown in the same position that they were deposited Regional uplift tilted the stratified beds after they were deposited. Correct! Correct! Erosion must have occurred after Layer A was deposited and before Layer B was deposited Correct! Correct! Erosion must have occurred after Layer B was deposited and before Layer A was deposited There is no evidence of erosion Layers at the top of this image are younger than layers at the bottom Correct! Correct! This image shows an angular unconformity Correct! Correct!
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 28/49 This image shows a nonconformity This image shows a disconformity 1 / 1 pts Question 16 Use the principles of relative dating that you have learned to order the formation of the layers in the following schematic:
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 29/49 1st (oldest) E Correct! Correct! 2nd H Correct! Correct! 3rd C Correct! Correct! 4th I Correct! Correct! 5th G Correct! Correct! 6th A Correct! Correct! 7th F Correct! Correct! 8th D Correct! Correct! 9th (youngest) B Correct! Correct! 0 / 1 pts Question 17
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 30/49 The image above, taken near Manitou Springs, CO, shows ~500 million year old sandstones from the Sawatch Formation sitting atop ~1 billion year old Pikes Peak granite. The difference in age between these two rock formations means that 500 million years of time is missing from the geologic record at this location! This feature is named the “Great Unconformity” and is outlined by the dashed white line. Using the information present in this outcrop, propose a timeline of events : 1 (oldest) Emplacement of the P ou Answered ou Answered Formation of the North American continent Correct Answer Correct Answer 2 Subsidence or sea lev ou Answered ou Answered Emplacement of the Pikes Peak granite Correct Answer Correct Answer
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 31/49 3 Deposition of the Was ou Answered ou Answered Uplift and Erosion of the Pikes Peak granite Correct Answer Correct Answer 4 Formation of the Nort ou Answered ou Answered Subsidence or sea level rise Correct Answer Correct Answer 5 Uplift and tilting of all ou Answered ou Answered Deposition of the Wasatch sandstone Correct Answer Correct Answer 6 Uplift and Erosion of t ou Answered ou Answered Uplift and tilting of all units Correct Answer Correct Answer 7 Exposure of bedrock ou Answered ou Answered Erosion of the present-day landscape Correct Answer Correct Answer
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 32/49 8 (most recent) Erosion of the present ou Answered ou Answered Exposure of bedrock from road cut Correct Answer Correct Answer 2. Determining Numerical Ages Geologists strive to establish the sequence of events that produce geologic features, such as rocks, structures, and landscapes. However, early geologists had no way of specifying the numerical age of a feature, i.e. the age as a numerical value of years. Fortunately, this situation changed with the discovery of radioactivity. Simply put, radioactive elements decay at a constant rate that can be measured in the lab and can be specified in years. The techniques that use measurements of radioactive elements to calculate the numerical ages of rocks are known as isotopic dating . To explain the techniques of isotopic dating, we must first understand the basics of radioactive decay . Atoms of a given element may have different atomic weights. These different versions of an element are called isotopes . Some isotopes of certain elements are stable, and can last essentially forever. However, radioactive isotopes are unstable and will eventually undergo a change called radioactive decay . This change converts an isotope into a new isotope of a different element. The radioactive isotope that decays is the parent isotope , while the decay product that is formed by the radioactive decay is the daughter isotope . 0.25 / 0.25 pts Question 18
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 33/49 What happens during radioactive decay? A stable isotope of one element changes into a new isotope of a different element A stable isotope of one element changes into a new isotope of the same element An unstable isotope of one element changes into a new isotope of a different element Correct! Correct! An unstable isotope of one element changes into a new isotope of the same element 0.25 / 0.25 pts Question 19 We cannot specify how long an individual radioactive isotope will survive before it decays, but we can measure how long it takes for a population of the parent isotopes to be halved. This is a consequence of half of the parent isotopes decaying into daughter isotopes. This time unit is called the half-life of the isotope. For a given radioactive element, the half-life is a constant regardless of conditions.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 34/49 The ratio of parent-to-daughter isotopes changes with the passage of each successive half-life. How many of the original atoms of a parent isotope remain unchanged after five half-lives? 1/4 1/8 1/16 1/32 Correct! Correct! 0.5 / 0.5 pts Question 20 Since radioactive decay proceeds at a constant rate, like the tick-tock of a clock, it provides a basis for telling time. We can calculate the age of a mineral by measuring the ratio of parent isotopes to daughter isotopes in the mineral (or organic matter in the case of radioactive carbon). There are many different pairs of parent and daughter isotopes among the known radioactive elements (see below table). To obtain an isotopic date, we must select the appropriate isotope pair depending on the samples to be studied.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 35/49 Answer 1: Answer 2: Answer 3: Which pair of parent and daughter isotopes is not useful for dating very old rocks? 14C-14N Why is this pair of parent and daughter isotopes not useful for dating very old rocks? Because not enough of the parent isotope remains to measure accurately Why are isotopes with long half-lives not useful for dating fossils or rocks that span the last glacial-interglacial cycle, approximately between 12,000 and 125,000 years old? Because not enough of the daughter isotope has formed to be detectable 14C-14N Correct! Correct! Because not enough of the parent isotope remains to measure accurately Correct! Correct! Because not enough of the daughter isotope has formed to be detectable Correct! Correct! At high temperatures, isotopes are capable of escaping from the mineral crystal that contains them. The “isotopic clock” starts only when crystals become cool enough that the isotopes are locked within the mineral crystal. The temperature below which isotopes are no longer free to move is called the closure temperature of a mineral. When we specify an isotopic date for a mineral, we are defining the time at which the mineral cooled below its closure temperature. With the concept of closure temperature, we can interpret the meaning of isotopic dates. In the case of igneous rocks, isotopic dating reveals the time at which the magma cooled below the closure temperature. In the case of metamorphic rocks, isotopic dating reveals the time at which a rock cooled from the metamorphic temperature down to a temperature below the closure temperature. However, if we date minerals in a
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 36/49 sedimentary rock, we are only dating the time that those minerals first crystallized as part of an original igneous or metamorphic rock. 0.63 / 1 pts Question 21 While hiking, you stumble upon an outcrop of rock. Being a good geologist, you pull your trusty field notebook from your vest and get to work making a field sketch (pictured above). Using the principles of relative dating, you know that the diorite was the first rock formed, then the conglomerate and finally the shale were deposited on top. While looking closely at the outcrop you find some nice fossils! You find a piece of bone in the conglomerate, and several clams in the shale. These rocks suggest that conditions changed from high-energy to low-energy , such as you might expect during sea level rise. Your working hypothesis is that this outcrop was formed on the edge of an ancient mountain range. Rivers drained from the mountains to a nearby sea, depositing a coarse conglomerate on the older diorite. As sea
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 37/49 Answer 1: levels rise, the rivers become submerged, and shales and marine organisms are deposited on top. To test your hypothesis, you will need to know when these rocks are from. So, you take some samples back to the lab to measure ages with radioactive isotopes. Before you get to work, you need to ask yourself a few questions: What relative dating principle can be used to determine the age of deposition of the conglomerate from the absolute age given by the fossil bone? The principle of superposition How should you interpret the date given by the diorite? It is time since crystalization of melt After toiling in the lab to crush the rocks, dissolve them in beakers, and finally put them through a mass spectrometer, you measure the parent- daughter isotope ratios of each of your samples. You write the resulting ages on your field sketch. Now that have both stratigraphy and absolute dates, you are finally able to apply your geological knowledge and scientific reasoning to test your hypothesis. Using these tools, answer the following questions: At what age was the shale deposited? 5 Ma How much time is missing between the formation of the diorite and the deposition of the conglomerate? 194 Ma What can you infer from the the age of the conglomerate rock sample The conglomerate was deposited at least 200 Ma, and its source material may be the diorite The shale rock sample is dated to be much younger than the diorite, which indicates that As the depositional environment changed, so did the source of sediment . Do the absolute dates confirm or contradict your hypothesis? Contradict high-energy to low-energy Correct! Correct!
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 38/49 Answer 2: Answer 3: Answer 4: Answer 5: Answer 6: Answer 7: Answer 8: The principle of superposition ou Answered ou Answered The principle of inclusion orrect Answer orrect Answer It is time since crystalization of melt Correct! Correct! 2 Ma orrect Answer orrect Answer 5 Ma ou Answered ou Answered 194 Ma Correct! Correct! The conglomerate was deposited at least 200 Ma, and its source material may be the diorite Correct! Correct! As the depositional environment changed, so did the source of sediment Correct! Correct! Confirm orrect Answer orrect Answer Contradict ou Answered ou Answered 3. Geologic Maps Geologic maps are depictions of the geology at the surface of the earth. They classify areas by rock age and rock type, and they locate features
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 39/49 like faults and volcanoes. Geologic maps use symbols to show features, and alphabetic codes to indicate the age and rock type of a map unit. For example, Qa is a common map unit that stands for Quaternary alluvium. Quaternary refers to the period of time from the present back to 2.6 million years ago, and alluvium refers to river sediment. The map legend includes a table of all map units, descriptions of them, and their color on the map. Unlike topographic maps, which are made with quantitative surveying techniques, geologic maps are qualitative interpretations based on an array of field observations, laboratory data, theory, and scientific reasoning. As new work is completed, different versions of maps will be published for the same areas. Large scale maps, such as 1:24,000 scale maps, show a relatively small area but lots of detail. In contrast, small scale maps, ranging from 1:100,000 to 1:10,000,000, show large areas or even the entire world, but provide much less detail. We have attached a link to the 1:500,000 scale geologic map of Washington State published by the Washington Department of Natural Resources in 2005: Washington State Geology Map (Schuster 2005). It is a beautiful map that you can have printed (at full scale) and laminated at any local print shop to hang as “geo-art”. 0.25 / 0.25 pts Question 22 Scroll around the map mentioned above and observe some of the important information about Washington State geology that it conveys. What geologic information does this map provide the students, researchers and the general public about Washington State geology? Select all answers that apply. General rock classification types Correct! Correct! Geologic age of the rock units Correct! Correct! Physical color of the rock units Mineral content of the rock units
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 40/49 Structures within the rock units (i.e. faults and folds) Correct! Correct! How can you use geologic maps? Job prospects are not great right now... What if you could put your geology skills to use… Imagine... Your pulse quickens when you learn that a T-Rex skeleton can fetch $3 million. While pondering your exciting new future as a fossil collector, you happen to mention your idea to a friend, who brightens with interest and gives you a hot tip: A recent landslide along I-5 has exposed a T-Rex skeleton, but it’s on a dangerous slope. Your friend needs your help, and a ride to the location, to get the skeleton. Could it be true? 0.25 / 0.25 pts Question 23 Before heading out to the landslide, you consult your 1:500,000 scale geologic map of Washington State . You also refresh your memory of the geologic timescale by referring to Figure 7-2. You see the following image of the Seattle area:
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 41/49 Hoping that ‘Qgd’ stands for Quality, Good Dinosaurs, you consult the map legend: Astonished, you… … shake your head in disgust. Seattle is underlain with granite, and any old dinosaur bones would have melted in the magma chamber from which the granite formed.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 42/49 … shake your head in disgust. Seattle is underlain with Pleistocene glacial sediment, but the dinosaurs died off at the end of the Cretaceous. The sediments in Seattle are too young to contain dinosaur bones. Correct! Correct! … jump with joy. The geology in the Seattle area is consistent with the T- Rex story! 0.5 / 0.5 pts Question 24 Broadening your search, you read that the Tertiary Chuckanut Formation contains fossilized palm fronds (Mustoe et al., 2007), worth up to $20,000. Rumor has it that a recent landslide has exposed a fresh exposure of the Chuckanut Formation near Bellingham. Time is of the essence, but you still pause to consult your geologic map.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 43/49 You head for the map unit…
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 44/49 Qa Tc Correct! Correct! Mzms 0.5 / 0.5 pts Question 25 On your drive towards Bellingham, you learn that the Chuckanut Formation contains fossils of Sabalites campbelli, an extinct palm plant. After some quick research, you also learn that this extinct palm looks a lot like Palmetto, a living tropical plant. Image credit: (https://en.wikipedia.org/wiki/Chuckanut_Formation#/media/File:Sablaites_campbelli_fossils.JPG) https://en.wikipedia.org/wiki/Chuckanut_Formation#/media/File:Sablaites_campbelli_fossils.JPG Fossils of Sabalites campbelli palm leaves from the Chuckanut Formation, south of Bellingham, Whatcom County, Washington.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 45/49 Source (https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:Sabal_palmetto00.jpg) : https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:Sabal_palmetto00.jpg Sabal palmetto from von Martius' "Historia naturalis palmarum". (https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:Sabal_palmetto00.jpg) You see that Palmetto species only survive in the tropics because they cannot withstand the cold winters of the mid and high latitudes.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 46/49 Source (https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:PalmTrees.png) : https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:PalmTrees.png (https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:PalmTrees.png) Survivability range of cabbage palmetto in the U.S. without winter protection. (https://en.wikipedia.org/wiki/Sabal_palmetto#/media/File:PalmTrees.png) You then realize that the Sabites fossils in the Chuckanut Formation indicate one of two things: either it was warmer in the past causing the range of the palm plants to expand northward, or, the Chuckanut Formation first accumulated in the tropics, and then shifted north via plate tectonics. In researching whether it was warmer near Seattle in the past, you find a global climate reconstruction for the Cenozoic.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 47/49 Source: Michael Archer, https://www.researchgate.net/figure/Climate-change-throughout-the-Cenozoic- as-measured-by-the-palaeotemperature-proxy_fig2_277347887 (https://www.researchgate.net/figure/Climate-change-throughout-the-Cenozoic-as-measured-by-the- palaeotemperature-proxy_fig2_277347887) Global temperature reconstruction for the last 65 million years (Zachos et al., 2001). (https://www.researchgate.net/figure/Climate-change- throughout-the-Cenozoic-as-measured-by-the-palaeotemperature- proxy_fig2_277347887) If you know that the Chuckanut Formation was deposited sometime during the Tertiary (66-2.6 million years before present), then based on this climate reconstruction data, which hypothesis is true? The past climate in Seattle was warm enough to support palm species. Therefore, the Chuckanut Formation was deposited at its current latitude. The past climate in Seattle was not warm enough to support palm species. Therefore, the Chuckanut Formation was deposited closer to the equator, and drifted northward via plate tectonics.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 48/49 The past climate in Seattle is variable throughout the Tertiary period. Without more precise dating of the Chuckanut Formation, we cannot determine whether or not it was deposited at its current latitude. Correct! Correct! 0.75 / 0.75 pts Question 26 What geological techniques could you use to explore whether the Chuckanut Formation formed at tropical latitudes and shifted northward via tectonics, or whether it formed near its current latitude? Paleomagnetism; measure the orientation of magnetic minerals to find the latitude at which the rock formed at Correct! Correct! Rock Texture; use grain size, rounding, etc, to infer the environment of deposition Fossil Record; find fossils of other species to compare survivability ranges Correct! Correct! Geologic Dating; narrow down the date of formation through absolute or relative dating better compare to global temperature reconstructions Correct! Correct! Bibliography Mounier, Aurélien, and Marta Mirazón Lahr. "Deciphering African late middle Pleistocene hominin diversity and the origin of our species." Nature communications 10.1 (2019): 1-13.
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2022/05/29 21:37 Laboratory 7: Geologic Time: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651011 49/49 Mustoe, George E., Richard M. Dillhoff, and T. A. Dillhoff. "Geology and paleontology of the early Tertiary Chuckanut Formation." Field Guides 9 (2007): 121-135. Zachos, James, et al. "Trends, rhythms, and aberrations in global climate 65 Ma to present." science 292.5517 (2001): 686-693. Quiz Score: 12.06 out of 14
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