geodin2 - The motion of plates over the Earths surface can be described by making use of Eulers theorem(Section 3.2.1 which says that the relative

# geodin2 - The motion of plates over the Earths surface can...

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The motion of plates over the Earth’s surface canbe described by making use of Euler’s theorem (Section3.2.1), which says that the relative motion between twoplates are uniquely defined by an angular separationabout a pole of relative motion known as a Eulerpole. The pole and its anti-pole are the two uniquepoints on the surface of the Earth that do not moverelative to either of the two plates. An important aspectof relative plate motion is that the pole of any twoplates tend to remain fixed relative to them for longperiods of time. Plate velocities are similarly constantfor periods of several million years (Wilson, 1993).There are three methods by which the pole ofrelative motion for two plates can be determined. Thefirst, and most accurate, is based on the fact that fortrue tangential motion to occur during the relativemovement of two plates, the transform faults alongtheir common boundary must follow the traces ofsmall circles centered upon the pole of relative motion(McKenzie & Parker, 1967; Morgan, 1968). The poleof rotation of two plates can thus be determined byconstructing great circles at right angles to the trendsto transform faults affecting their common margin andnoting their point of intersection. The most convenienttype of plate margin to which to apply this techniqueis the accretive type (Fig. 5.3), as ocean ridgesare frequently offset laterally by transform faults