ESC. 2000 Chp 9 Quiz.docx - Question1 1/1pts .Iftheratioof...

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Question 1 1 / 1 pts A radioactive isotope of the element potassium decays to produce argon. If the ratio of  the number of argon to potassium atoms is found to be 7:1, how many half-lives have  occurred since the sample of radioactive potassium started to decay?    7    8    3    1 FEEDBACK: Three half-lives have passed if the ratio of argon to potassium atoms is  7:1. At the end of one half-life, the ratio of the number of argon to potassium atoms is  1:1. After two half-lives, it is 3:1, and after three half-lives, 7:1.   Question 2 1 / 1 pts An area of slightly dipping sedimentary rock layers has large inclusions and is intruded  by an igneous dike. Using the basic principles for determining relative ages you can  infer that the   sedimentary rock "baked" by the igneous intrusion is older than the intrusion.     oldest sedimentary layer is the top layer.    sedimentary layers started out steeply dipping.    dike is older than the sedimentary rock layers it cuts across.
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FEEDBACK: The igneous intrusion would have "baked" (metamorphosed) the  sedimentary rocks adjacent to the intrusion, so the intrusion is younger than the  metamorphosed rock. Sedimentary layers are deposited horizontally and not steeply  dipping. The youngest sedimentary layer, not the oldest, is on the top. The dike must be younger than the sedimentary rock layers that it cuts across because the rock layers  must have been there before they could be cut by the intrusion.   Question 3 1 / 1 pts An organism is most likely to be fossilized if it    is exposed to the atmosphere.    dies in an oxygen-poor environment.    contains mostly soft flesh with few hard parts.    is buried slowly. FEEDBACK: Organisms are most likely to be fossilized if their remains can be buried  before they are scavenged or weathered and before they decay. Therefore, an  organism is most likely to be fossilized if it dies in an oxygen-poor environment that has  few decomposers, is buried rapidly, and contains hard, durable parts.   Question 4 1 / 1 pts Footprints, feeding traces, burrows, and dung are considered to be    permineralized fossils.    molds and casts.   
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trace fossils.    chemical fossils. FEEDBACK: Footprints (tracks), feeding traces, burrows, and dung (coprolites) are  considered to be trace fossils. Chemical fossils are distinctive chemicals left behind  from the breakdown of an organism. Molds and casts form when sediment hardens  around a fossil; when the fossil dissolves, it leaves behind a cavity called a mold. The  mold may later be filled with minerals from groundwater, forming a cast. Permineralized 
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