ESSE 1010 Lecture Notes - Lecture 10: Magnetite, Curie Temperature, Paleomagnetism

• School: York University
• Department: Earth, Space Science and Engineering
• Course: ESSE 1010
• Professor: Gary Jarvis

Document Summary

Above the tc, the curie temperature, magnetic minerals (e. g. magnetite) lose their magnetic properties (atomic dipoles become randomized, no longer lined up). Only within 20km (too hot past that depth) of the earth"s interior are the rocks permanently magnetic, called the magnetized layer. This still isn"t enough magnetism to account for earth"s dipole field. There is a large steel current flowing within the planet. Iron and nickel are very good at conducting electricity and is rich in the core of the earth. The current flow (electric current) is the highest contributing reason for earth"s dipole field. 4 x 109 amps of electric current in the core, particularly in the liquid outer core. Secular variations of the earth"s magnetic field: rapid variations in direction and magnitude of b in historic time. Paleomagnetism: ancient or past geomagnetic fields, a record of the prevailing magnetic field is frozen into rocks at the time they first solidify from the molten state.