connected c anomaly stripes in the oceans with the plate tectonic model. EXERCIS
ID: 152484 • Letter: C
Question
connected c anomaly stripes in the oceans with the plate tectonic model. EXERCISE 2.4 Interpreting Ocean Ridge Magnetic Stripes Name: Course: Date In Figure 2.8a, compare the orientation of the magnetic anomaly stripes for the Mid-Atlantic Ridge with the orientation of the ridge crest Cillustrated with a red line) In Figure 2.8b, do the same for the Juan de Fuca Ridge and its anomalies (a) Are the individual anomalies oriented randomly? Are they parallel to the ridge crests? Oblique to the ridge crests (b) Explain how the process of seafloor spreading can produce these orientations and relationships (c) Some magnetic stripes are wider than others. Knowing what you do about seafloor spreading and magnetic reversals suggest an explanation.Explanation / Answer
A) Magnetic anomaly strips are oriented parallel to the central ridge. Each of these stripes represent a certain period of time and that time's magnetic orientation.
B) The concept of seafloor spreading was first introduced in 1960s'. According to the concept, new seafloor is being created continuously. This happens because of the divergence of two plates at the mid oceanic ridges. When two plates diverge from each other they also carry the newly formed seafloor,formed from the magmatism at the ridge.
These strips of newly formed crust encompasses some magnetic minerals. These minerals contain some elements, that responds to the outer magnetic field of the earth. These minerals orient themselves according to the external magnetic poles in the molten state. When the magma cools the mineral's orientation get stored in the solid rock. These rockstrips then gets away from the ridge because of the divergence of the plates.
Earth's magnetic field must have changed through time. As the magnetic poles change their positions, molten minerals at the ridge orient themselves according to that and reverse to the previous strip of rock away from the ridge. So, getting away from the ridge we get the older magnetic directions of the earth.
c) Change in the magnetic poles does not take place very frequently nor very systematically. These shifts are mainly due the change in chemistry or magnetism of the rocks. So, these changes may not sometimes take place for a long period of time. In that case, broad band of rocks will show same orientation of magnetic minerals and produces wider bands of magnetic strips at the mid oceanic ridges.
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