GEOL 101 Lecture Notes - Lecture 9: North Magnetic Pole, Outer Core, Inner Core
Document Summary
S-waves: do not travel through liquid (inner/outer core) Earth"s core: the outer core is liquid as indicated by the s-wave shadow, the core is composed of iron, some nickel. And about 15% of lighter elements: the change in density between mantle and core is greater than that between air and rock at the surface, the solid inner core is almost completely iron. Inner core spin: a sphere inside the solid inner core that spins (at a different rate than the earth) and helps make a magnetic field. Sources of earth"s heat: the initial source of heat was input by the collisions of many planetessimals. Kinetic energy of these collisions was converted to heat: heat was also added by the decay of short-lived radioactive elements, collision of a mars-sized object led to the formation of the moon. Earth has cooled since then: additional heat is added from longer term radioactive decay.
