|MadSci Network: Earth Sciences|
Rachel, Keep asking interesting questions. If the core of the earth were considerably smaller, a number of things would be different. Actually, it would be rather hard to tell the difference between a core the size of a pea and no core at all. The most obvious difference is that the pull of gravity would be less. The core is made mostly of iron and nickel which is about twice as dense as rock. The earth as a whole would have less mass. It would also expand a bit because everything would weigh less. Another is that the earth's magnetic field would be much weaker, if not entirely gone. The magnetic field is believed to be due to large scale motions in the very conductive liquid outer core. Rocks are much less conductive than iron so even if the replacement for the core were liquid, it is unlikely that there would be much of a geodynamo effect. The core contributes a significant fraction of the earth's moment of inertia, or it's resistance to changes in the axis of rotation. The poles would wander more due to the gravitational interactions with the Sun, Moon and planets. It is likely that there would be fewer mountains, volcanoes and earthquakes. Heat from deep in the earth drives plate motions. Rock conducts heat less well than iron so the temperature distribution in the replacement for the core would be different. David
Try the links in the MadSci Library for more information on Earth Sciences.