In your own words, explain the effects of changes in Earth's magnetic field over time.

The Earth's magnetic field plays several roles:

Rock and sediment datingShielding from the Sun's charged particlesBearingSolar winds

ALL of these are factors that would be affected by changes in Earth's magnetic field.

Explanation:

The study of the Earth's Magnetic polarity is recorded in igneous rocks, reversals of the magnetic field allows for dating of rocks and sediments.The Sun emits charged subatomic particles which the Earth's magnetic fields deflects to the North and South poles,causing the Northern (and Southern) lights upon entering the atmosphere.Humans use the magnetic fields to tell what direction is North using compassesThe Earth's magnetic field deflects solar winds which would otherwise deplete our ozone layers, leaving us vulnerable to ultraviolet radiation.

ALL of these are factors that would be affected by changes in Earth's magnetic field.