GEO_103_Exam_2_Key

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Name: Version #1 GEO 103 – Semester Exam #2 (each question is worth 1 point out of a possible 25 points) 1) Imagine you are examining a vertical cliff face of rock in the field. At the base of the cliff is a fossil-rich limestone, deposited offshore in a reef. In the middle is a layer of carbonate mudstone deposited in a coastal lagoon setting. At the top is a layer of ooid-rich sandstone deposited in a beach setting. Using Walther’s Law, you determine from these vertical relationships between the different rock types that sea level was ______ during deposition: A. Rising B. Falling 2) Is there a way for sea level to be stationary in the example given in question #1? A. Yes, if the land was being tectonically uplifted while sea level stayed the same B. Yes, if sea level stayed the same while the rate of growth of the carbonate reef was very high, causing it to migrate away from the coast (=prograde) over time C. No, the only way to explain the vertical relationships in question #1 is through sea level change D. A and B could both be true 3) Would you expect a carbonate-dominated shelf to form in a cold-water environment off the coast of a tectonically active area, where there are high mountains near the coast that are being eroded and delivering large quantities of clastic sediment to the continental shelf? A. No, because more CO 2 can dissolve in cold water, making carbonic acid, which tends to make calcite dissolve, rather than precipitate B. Yes, these are all conditions in which reef-dwelling organisms thrive, which favors the production of large volumes of carbonate sediment C. No, because the large volumes of clastic sediment being delivered by mountain erosion will tend to make the water cloudy or muddy, which makes it hard for photosynthetic organisms that make shells out of calcite to thrive D. A and C are both true 4) You are examining sections of sandstone in the field that each show the following characteristic sedimentary structures and textures: poorly sorted coarse sand grains at the base, fine sand grains at the top, and lots of silt and mud mixed in with the sand grains. In between units of sandstone, there are layers of mudstone containing fossils of marine plankton. How were these sandstones deposited and where were they deposited? A. They were deposited by turbidity currents on the continental rise B. They were deposited in a meandering river and flood plain setting C. They were deposited by turbidity currents on the continental slope D. They were deposited in a desert in an alluvial fan setting

2 5) The ______ time scale describes how old one set of rocks is in comparison to another, whereas the ______ time scale tells exactly how old each set of rocks is A. Absolute; Relative B. Relative; Absolute C. Molecular dating; Geologic D. Geologic; Molecular dating 6) Which type of stratigraphy uses the physical characteristics of rocks (rock type, rock structure, rock texture) to establish correlative relationships between geographically separated bodies of rock? A. Magnetostratigraphy B. Biostratigraphy C. Lithostratigraphy D. Chemostratigraphy 7) Which of the following properties is NOT a characteristic of an index fossil A. Highly distinctive form, making them easy to identify B. The species was adapted to live in a wide range of environments when it existed, so their fossils appear in many different rock types at the same time C. The species was abundant, so it left behind a fossil record that is also abundant D. The species underwent slow evolutionary change and survived numerous mass extinctions, so it is “wide-ranging” in time, meaning that it is distributed across wide vertical distances in outcrops of sedimentary rock 8) William Smith “The Father of English Geology” is credited with which of the following (multiple answers are possible): A. Recognizing that fossils could be used to establish the relative ages of strata separated from each other over wide geographical distances B. Recognizing that species could go extinct during the course of Earth history C. Identifying and describing the first named “Geologic System”, called the “Cambrian”, which marked the first appearance of fossil-rich rocks in strata from Wales, UK D. Creating the first geological map of the United Kingdom 9) Which of the following represent stratigraphic “events” that can be used to correlate strata? (Hint: “Events” are widespread, distinct features that were formed or deposited rapidly). A. Volcanic ash beds B. Sea level rise or fall reversals caused by Milankovitch cycles C. Layers of distinct chemical composition, like the Iridium layer formed by the meteorite impact that killed the dinosaurs D. All of the above

3 10) Using the graph at right, determine the age of a mineral that has a half life of 5,700 years and a measured parent/daughter ratio of 1/16: A. 5,700 years old B. 11,400 years old C. 17,100 years old D. 22,800 years old 11) A common problem in Potassium-Argon age dating is that the daughter isotope, Argon, is an element that prefers to be in the gas phase. This means that it can easily escape from a crystal after it forms from the radioactive decay of its parent potassium atom. If you were trying to age-date a mineral that had lost some of its argon after it formed, what effect would the argon loss have on the age that you measure? A. It would be too young compared to its actual age B. It would be too old compared to its actual age 12) Zircon (ZrSiO4) is a widely used mineral for determining the ages of rock formations that it is found in. Which of the following make zircon such a reliable mineral for age dating? A. When it crystallizes from a magma, it incorporates the radioactive parent element uranium in its crystal structure B. When it crystallizes from a magma, it excludes the daughter element of uranium, which is lead, so that any lead that is measured in zircon must have been formed after the mineral crystallized C. Zircon is a mineral that is highly resistant to weathering and metamorphism, so it doesn’t easily lose its parent or daughter isotopes, even if the zircon is very old D. All of the above 13) Which of the following mechanisms provides a way for genetic variations to arise in a species without the involvement of parents passing their DNA to their offspring: A. Reproduction (meiosis) B. Horizontal gene transfer C. Cell division (mitosis) 14) All but one of the following are examples of Rapid Speciation and/or Evolutionary Radiation: A. Evolution of ~500 species of Cichlid fishes in Lake Victoria over the past 13,000 years B. Accumulation of small changes in mollusk oyster shells through reproductive variations passed between generations over a 12-million-year period in the Jurassic C. Development of distinct beak shapes and sizes in 18 finch species in the Galapagos Islands from a common ancestor that arrived on the islands about 1 million years ago D. Development of porous skeletons in corals that enabled them to outcompete other species for resources and evolve dozens of new species during a short interval in the Triassic period

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4 15) Muscles that allow animals to move their ears to follow sounds to their source are common in mammals such as bats, cats, and dogs. In humans, however, these muscles are an example of: A. Homologies B. Vestigial organs C. Speciation D. Extinction 16) Using the molecular clock method for determining how long ago two species, A1 and A2, diverged, what would be the time estimate if neutral genes in species A1 differed from species A2 by 30 percent and the mutation rate was 1 percent per million years? A. 3 million years B. 30 million years C. 300 million years D. 3 billion years 17) All but which of the following were used by Wegener and DuToit as evidence in support of the Theory of Continental Drift? A. The jigsaw puzzle fit of the coastlines of continents separated by ocean basins B. The existence of identical biostratigraphic and lithostratigraphic units on the continents of Africa, South America, Antarctica and India C. Sedimentary structures that indicated that all of the continents had a single large glacier on them at one time D. Mirror image patterns of magnetic polarity reversals in magnetized rocks found on both sides of the Earth’s mid-ocean ridge systems 18) “Ridge Push” is one of the 4 major forces that drives Plate Tectonics. It is best described by which of the following choices below: A. Force provided by the high standing oceanic crust along the Earth’s mid-ocean ridges B. Drag forces along the base of the ocean crust caused by convective movement in the Earth’s mantle C. Force provided by the weight of the oceanic crust as it subducts into the mantle D. Force provided by broken off pieces of oceanic crust that have been subducted that suck the unbroken part of the ocean crust down behind it 19) In a continental arc tectonic setting, where oceanic crust is subducting beneath continental crust, ______ faults are common, _______ are formed in the continental crust above the subduction zone and _____ accumulate in forearc and foreland basins on either side of the arc A. Strike-slip (or transform); pull-apart basins; lavas B. Thrust (or reverse); volcanoes and plutons; marine sediments and turbidites C. Normal; fault bounded valleys; clastic and evaporitic sediments

5 20) Which of the following correctly lists the type of fault shown? A. Strike Slip (A), Normal (B), Reverse (C) B. Normal (A), Reverse (B), Strike Slip (C) C. Reverse (A), Strike Slip (B), Normal (C) 21) Marine sedimentary rocks lying above evaporitic sedimentary rocks beneath the Red Sea (located between east Africa and western Saudi Arabia) tell us: A. The Red Sea is slowly drying up B. The Red Sea is the failed arm of a triple junction (like the Connecticut rift valley) C. The Indian Ocean once covered a large part of Africa and Saudi Arabia D. The Indian Ocean recently flooded the Red Sea as rifting pushed Africa and the Arabian Peninsula apart. 22) Which chemical reaction represents what happens during photosynthesis? A. CH 2 O + O 2 → CO 2 + H 2 O B. 2CO 2 + H 2 O + CaSiO 3 → Ca 2+ + 2HCO 3 - + SiO 2 C. CO 2 + H 2 O → CH 2 O + O 2 D. Ca 2+ + 2HCO 3 - → CaCO 3 + CO 2 + H 2 O 23) Which flux can shrink the size of the CO 2 reservoir in the Earth’s oceans and atmosphere AND significantly alter the isotopic composition of that CO 2 reservoir by enriching it in Carbon-13? A. Rapid burial of organic matter B. Rapid chemical weathering of uplifted mountainous areas C. High rates of volcanism and metamorphism D. High rates of respiration of organic matter caused by warm climate conditions 24) The scenario described in question #23 occurred during the _____ period of Earth history and also resulted in a significant ________ in the concentration of O 2 in the Earth’s atmosphere: A. Precambrian; decrease B. Carboniferous; decrease C. Carboniferous; increase D. Cenozoic; increase 25) Anoxic water bodies lack which of the following? A. CO 2 B. Methane C. Pyrite D. O 2