GLG 301 Lecture Notes - Lecture 15: Remanence, Keith Runcorn, Magnetization
Document Summary
Plate tectonics (see also, dynamic earth booklet under supplementary readings) Remanent magnetism ( permanent magnetism ) this magnetism remains even after the external inducing field is removed. Magnetism can also be acquired by ion alignment during precipitation (e. g. , limestone) or alignment of mineral flakes during sedimentation: paleomagnetic poles, the magnetic pole when the rock formed. Axial geocentric dipole (agd) assumption: the magnetic field of the earth is The paleolatitude, , is simply tan i = 2 tan ; need only the inclination (i). Obtain many samples from many locations and average to account for high frequency variations of the field: apparent polar wandering (apw) curve (noted by keith runcorn in. Since the remanent ( frozen in ) magnetic direction allows us to determine the paleolatitude at which the rock crystallized, if we measure rocks of various ages on a continent, we can see if the pole has moved. This was noted by keith runcorn in 1955.
