Hi folks! I'm a visitor on this page, but as i come from geomagnetic background there are a few things a would like to mention:
1) the Earth's magnetic field is NOT created by telluric currents! It is created by currents in the liquid outer core (as mentioned in an paragraph above) but that are not telluric currents. telluric currents are induced in the crust / mantle by electromagnetic waves from the atmosphere - due to thunderstorms, e.g., or (as mentioned in the article about telluric currents) solar wind or currents in the ionosphere.
changes of the main field, that is the field generated in the deep interior, are much to slow to induce currents in the crust or mantle. they occur over time scales of years rather than days or even hours.
if you have further questions, don't hesitate to contact me: reyko@gmx.net (subject should include "wikipedia").