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Monday 19AUG13 2nd - Get your reading guides out and read through Section 1 for your quiz. C Continue with Section 2 PowerPoint. Graphing Activity 3rd - 4th - Get your reading guides out and review section 2 for your quiz. Continue with Graphing Activity. Section 3 PowerPoint • Section 3 - Reading Geologic Records 2 http://www.stratigraphy.org/index.php/ics-chart-timescale 19. Scientists have divided Earth’s history into a series of time segments that are collectively referred to as the geologic time scale . 3 20. Each of these units is defined based on geologic and fossil records, with division between the units marking some major change such as the appearance of a new class of living creatures or a mass extinction. http://www.blog.gurukpo.com/wp-content/uploads/2013/08/geological-time-scale.jpg 4 Grand Canyon 21. Most of what we know about our planet’s history is based on studies of the stratigraphic record - rock layers and fossil remains embedded in them. 5 Photo: Arizona October 2012 Pamela R. Cox 22. Rock records can provide insights into what (3) questions? 1. How were geological formations created and exposed? 2. What role was played by living organisms? 3. How has the compositions of oceans and the atmosphere changed through geologic time? Photo: Arizona October 2012 Pamela R. Cox 6 23.Scientists use stratigraphic records to determine two kinds of scales. 24. Relative time scale refers to sequences – whether one incident occurred before, after, or at the same time as another. 25. Geologic time scale refers to – observations from sedimentary rocks. 26. But is discontinuous and incomplete because plate tectonics are constantly reshaping Earth's crust. http://traveltherockies.com/destinations/grand-canyon/grand-canyon-couples-favorite/ 7 8 http://www.education.com/study-help/article/earthscience-help-stratigraphic-classification/ 27.Explain how plate tectonics are constantly reshaping the earth. As the large plates on our planet's surface move about, they split apart at some points and collide or grind horizontally past each other at others. These movements leave physical marks: volcanic rocks intrude upward into sediment beds, plate collisions cause folding and faulting, and erosion cuts the tops off of formations thrust up to the surface. 9 http://www.expeditions.udel.edu/extreme08/geology/tectonics.php What plates are around the United States? http://www.youtube.com/watch?v=1-HwPR_4mP4Slide 10 10 28. Give (3) examples of some basic rules for determining relative ages of rock layers. a. older beds lie below younger beds in undisturbed formations b. an intruding rock is younger than the layers it intrudes into c. faults are younger than the beds they cut across. 11 29. In this geologic crosssection: a. How did layers E, F, H, I and J come to be? They were deposited through sedimentation. b. L and K represent Fault lines c. What do layers D, C and B represent? Layers of sediment added last. d. What does A represent? A volcanic intrusion younger than Sample geologic cross-section Geologic the layers it cross-sections are vertical slices through rock penetrates. formations. Earth scientists analyze crosssections to map an area's geological history. 12 30. Use the sample geologic cross-section and explain how fossil records can be used to determine relative age. Since fish evolved before mammals, a rock formation at site A that contains fish fossils is older than a formation at site B that contains mammalian fossils. 31. Give an example of how environmental changes can leave telltale geologic imprints in rock records. When free oxygen began to accumulate in the atmosphere, certain types of rocks appeared for the first time in sedimentary beds and others stopped forming. 13 http://thenewennui.blogspot.com/2012/07/fourteen-fossils.html 32. Researchers study mineral and fossil records together to trace interactions between environmental changes and the evolution of living organisms. Ammonite fossils among other creatures in a slab, 18 inches by 16 inches and a stump of petrified wood http://www.hansenjewelry.com/minerals_%26_fossils.html 14 33. What is radiometric dating and what does it allows scientists to do? Radiometric dating measures the decay of radioactive isotopes in rock samples. http://www.youtube.com/watch?v=cpnIxlDVmHw This approach has been used to determine the ages of rocks more than 3.5 billion years old . Once they establish the age of multiple formations in a region, researchers can correlate strata among those formations to develop a fuller record of the entire area's geologic history. 15 http://www.uky.edu/KGS/geoky/beneath.htm