Earth’s Magnetic PolesWALT: explain why Earth’s magnetic poles and geographic poles are at different locations.

Geographic Poles

Geographic poles are on either end of Earth’s axis.

True north is the direction of the geographic North Pole.

Magnetic PolesEarth has its own magnetic field, which produces magnetic poles.

Earth’s magnetic poles are not lined up directly with Earth’s axis, so there is a difference between the locations of the geographic and magnetic poles.

When using a compass, you need to make a correction for the difference between the poles. This angle of correction is called magnetic declination.

Magnetic Declination: the difference between the magnetic north and the true north.

Magnetic Declination

Magnetic Declination

The difference between true north and geographic north is caused by the slow moving metallic fluid (iron) of the outer core.

The way the fluid moves causes the difference in magnetic declination in various places and times.

Link to find New Jersey’s magnetic declination:

http://magnetic-declination.com/

Magnetic Pole Reversals

Like magnetic declination, the rotation of the Earth causes the liquid iron outer core to move.

This causes variation in the intensity and location of the magnetic poles

Sometimes, the poles even reverse entirely! So the compass would point North but would be facing the South Pole!

Evidence for Theory:

On the sea floor, sea floor spreading can be seen in bands of hardened lava.

The lava contains iron oxide that will point towards magnetic north. Therefore, evidence of this reversal can be seen by varying bands on the sea floor that point opposite ways.

These bands seen by sea floor spreading help to provide evidence for continental drift and plate tectonics.

The Statistics:

The Earth’s magnetic field has reversed approximately 170 times in the last 100 million years.

The magnetic field has been decreasing and thus scientists think we may be due for another magnetic reversal in the next 2000 years!

If so…all of our compasses will be obsolete!!!