Short Answer Topics- Final Paleomagnetism and geomagnetic pole paths Earth’s magnetic ?eld ● Flow in the liquid outer core creates the magnetic ?eld. o It is similar to the ?eld produced by a bar magnet o The magnetic pole is tilted ~11.5 from the axis of rotation ● Geographic and magnetic poles are not parallel. ● A compass points to magnetic N, not geographic N. ● The di뮎erence between geographic N and magnetic N is called declination. It depends on: o Absolute position of the two poles ▪ Geographic north ▪ Magnetic north ● Longitude ● Curved ?eld lines cause a magnetic needle to tilt. ● Angle between magnetic ?eld line and surface of the Earth is called inclination. It depends on: o Latitude Magnetic poles ● The magnetic pole intersects Earth’s surface just like the geographic pole does o Magnetic N pole and magnetic S pole both exist o Magnetic poles are located near geographic poles o Magnetic poles move constantly. ● Rock magnetism can be measured in the laboratory ● The study of fossil magnetism is called paleomagnetism. ● Iron (Fe) minerals in rock preserve information about the magnetic 腹eld at the time the rocks formed o Declination and inclination preserved in rocks often vary from present latitude/ longitude. o Instruments used in paleomagnetism record changes in position o These data are used to trace continental drift Paleomagnetism ● Rock magnetism can be measured in the laboratory. ● The study of fossil magnetism is called paleomagnetism ● Iron (Fe) minerals in rock preserve information about the magnetic ?eld at the time the rocks formed o Declination and inclination preserved in rocks often vary from present latitude/ longitude o Instruments used in paleomagnetism record changes in position o These data are used to trace continental drift ● Iron minerals archive the magnetic signal at formation ● Hot magma o High temp—no magnetization
▪ Thermal energy of atoms is very high ▪ Magnetic dipoles are randomly oriented The Juan de Fuca ridge and plate Basic principles of plate tectonics DIVERGENT BOUNDARY ➢ Tectonic plates move apart ➢ Lithosphere thickens away from the ridge axis ➢ New lithosphere created at divergent boundary ➢ Also called: mid-ocean ridge, ridge.
CONVERGENT BOUNDARY ➢ Tectonic plates move together ➢ The process of plate consumption is called subduction ➢ Also called: convergent margin, subduction zone, trench. TRANSFORM BOUNDARY ➢ Tectonic plates slide sideways ➢ Plate material is neither created nor destroyed ➢ Also called: transform fault, transform. The Juan de Fuca ridge is a tectonic spreading centre located o뮎 the coasts of the state of Washington and the province of British Columbia
➢ It runs northward from a transform boundary, the Blanco Fracture Zone, to a triple junction with the Nootka fault and the Sovanco Fracture Zone ➢ To its east is the Juan de Fuca Plate, which together with the Gorda Plate to its south and the Explorer Plate to its north, is what remains of the once-vast Farallon plate which has
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- Fall '09
- Plate Tectonics, Igneous rocks, Volcano, false statement