MadSci Network: Earth Sciences

Re: What would happen if the core of the earth was the size of a pea?

Date: Wed Feb 8 21:38:25 2006
Posted By: David Dunbar, Staff, Geophysics, GeoCenter, Inc.
Area of science: Earth Sciences
ID: 1139194969.Es


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. 


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