The Earth has tilted on its axis differently over the last few decades due to melting ice caps

• Earth's axis — the invisible line around which it spins — is bookended by the north and south poles.
• The axis tilts, and thus the pole shift, depending on how weight is distributed across Earth's surface.
• Melting glaciers have changed that distribution enough to knock Earth off its axis, research showed.

Since 1980, Earth's north and south poles have drifted about 13 feet.

The poles are where the planet's surface intersects with its axis of rotation — the invisible line running through the center of Earth's mass, which it spins around. But their geographic locations aren't fixed: As the Earth's axis moves, so do the poles.