Chapter 17 Unraveling Geologic History

More documents

Recommendations

Info

$File day 5 notes unit 2 math 8.pdf$

404 CHAPTER <strong>17</strong>: UNRAVELING GEOLOGIC HISTORY TERMS TO KNOW Scientists use the ratio of carbon-12 to carbon-14 to establish with great precision when the plant died. Radiocarbon dates have been verified by checking them with dates obtained from counting tree rings. The oldest trees alive today are more than 5000 years old. Radiocarbon dating has been especially useful in work on prehistoric human habitations and events during or since the last ice age. OTHER ISOTOPES The remaining three isotopes in Table <strong>17</strong>-1 have longer half-life periods. This means that they are more useful for dating older rocks, from 100,000 years old and back to the origin of Earth. These three radioisotopes are found in selected minerals. Each can be measured with great precision. The age of an igneous rock is generally the age of its minerals. In some places, these isotopes have been used to find the age of layers of volcanic ash. Therefore, ash beds are often useful horizons of absolute time that can be found over a broad geographic area. absolute age intrusion radioisotope decay product isotopes relative age decay-product ratio original horizontality superposition geologist outcrop unconformity half-life period radioactive uniformitarianism inclusion CHAPTER REVIEW QUESTIONS 1. Which geological events destroy a part of the rock record? (1) uplift and erosion over a long period of time (2) continuous deposition of sediments in a deep ocean basin (3) folding of rock layers deep under Earth’s surface (4) a long period of volcanic activity
Base your answers to questions 2–4 on the cross sections below that show widely separated outcrops at locations X, Y, and Z. Location X Location Y Location Z Gray limestone Conglomerate Red sandstone Black shale -containing trilobite fossils Tan limestone -containing ammonoid fossils Green shale -containing trilobite and coral fossils Gray siltstone -containing trilobite and brachiopod fossils 2. Which rock layer is probably oldest? Unconsolidated glacial deposits (till) Brown siltstone -containing mammal skeletal fossils Gray limestone Conglomerate Red sandstone -containing dinosaur footprints Black shale -containing trilobite fossils Tan limestone -containing ammonoid fossils (1) gray siltstone (3) tan limestone (2) green shale (4) brown siltstone 3. An unconformity can be observed at location Z. Which rock layer was most probably removed by erosion during the time represented by the unconformity? (1) conglomerate (3) black shale (2) gray siltstone (4) brown siltstone 4. The fossils in the rock formations at location X indicate that this area was often covered by (1) tropical rain forests (3) desert sand (2) glacial ice (4) seawater CHAPTER REVIEW QUESTIONS 405 Brown siltstone -containing mammal skeletal fossils Gray limestone Red sandstone Black shale -containing trilobite fossils Tan limestone -containing ammonoid fossils Green shale -containing trilobite and coral fossils
Page 1 and 2: Chapter 17 UNRAVELING MYSTERIES Unr
Page 3 and 4: have been able to piece together a
Page 5 and 6: Original Horizontality HOW CAN WE D
Page 7 and 8: Figure 17-3 It is clear that this f
Page 9 and 10: Contact Metamorphism Metamorphism i
Page 11 and 12: Figure 17-6 Formation of an unconfo
Page 13 and 14: sion is indicated by an uneven boun
Page 15 and 16: Intrusion and extrusion at the surf
Page 17 and 18: Figure 17-9 Carbon atoms always con
Page 19 and 20: HOW DO GEOLOGISTS ESTABLISH ABSOLUT
Page 21: HOW DO GEOLOGISTS ESTABLISH ABSOLUT
Page 25 and 26: Which sequence of events below is b
Page 27 and 28: 12. The graph below represents data
Page 29 and 30: Use the diagram below for questions

Chapter 17 Unraveling Geologic History

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?