Lab 1 Geoworld Plate Tectonics.docx - u201cGeoworldu201d...

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“Geoworld” Plate Tectonics LabModified after a lab by Ann Bykerk-Kauffman, Dept. of Geological and Environmental Sciences, California StateUniversity, Chico*PLEASE SUBMIT YOUR WORK AS A SINGLE FILE. PDF OR DOCPREFERRED, MULTIPLE PHOTOS ARE NOT ACCEPTED. Purpose:To better understand the principles of the plate tectonics theory byapplying them to the past, present and future analysis of a theoretical planet…..as it existed during the second age of Middle Earth.References: Chapter 2 in your textbook Natural Hazards, 4thed., and thePowerPoint lectures on Plate Tectonics as necessary.IntroductionDuring this lab exercise, we will analyze the plate tectonics of part of amythical planet called Geoworld. A tectonic map of the area is shown on p. 9.Geoworld has a plate tectonics system just like ours on Earth, only Geoworld isflat instead of spherical. In answering the questions below, you may assume thatthe movement rates for plates (both relative and absolute) are constantthroughout the time between your past and future reconstructions (they were,however, quite different at one time - see Part 1, A., questions 6 and 7). Allquestions are in bold face. Please put your answers in any blanks provided.A. Sea Floor Magnetic AnomaliesThe magnetic field of Geoworld is aligned in a north-south direction. Thepolarity of this field reverses at random intervals through time, just as the one onEarth does. The history of polarity of the magnetic field is well known for thepast 150 million years and is shown on the adjacent magnetic polarity timescale. The gray intervals represent normal polarity (the magnetic field pointsnorth) while white represents reverse polarity (the magnetic field points south).Detailed aerial and ship-board magnetic surveys have been conducted overthe oceans of Geoworld. Parts of the seafloor have an extra strong magneticfield while other parts have an extra weak magnetic field. Just as on Earth, theareas with anomalously strong magnetic fields are composed of rocks that aremagnetized with the same polarity as the current field while areas withanomalously weak magnetic fields are composed of rocks that are magnetizedwith the opposite polarity as the current field. Portions of the sea floor with ananomalously strong magnetic field are shaded; portions of the sea floor with ananomalously weak magnetic field are unshaded.Note that the magnetic anomalies form a striped pattern on the map ofGeoworld. Note also that the pattern in the Elrond Sea is symmetrical while thatin the AragornOceanisasymmetrical.This is becausethere is anactive spreadingridge in theElrond Sea butnotintheAragorn Ocean.The center ofsymmetry in theElrond Sea isalongthespreading ridge,indicated witharrows on themap on p. 9(You may wantto make extracopies of themaps and themagneticpolaritydiagram.)1.On the map on page 9, highlight the mid-ocean ridge in the ElrondSea and label it the Hobbit Ridge.

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