1.3 Magnetic Striping

How does magnetic striping support the plate tectonic theory?

What is normal and reverse polarity?

Normal Polarity

• magnetic North points roughly towards the

  • geographical North 

• magnetic South points roughly towards the

  • geographical South

Reverse Polarity

• magnetic North points roughly towards the

  • geographical South

• magnetic South points roughly towards the 

  • geographical North 

Overtime, Earth’s polarity has flipped multiple times

• alternating between normal and reverse polarity

What is magnetic striping?

• the zebra-like pattern where

  • there’s strips of normal polarity rocks 

    • alternating alongside strips of reversed polarity rocks on the seafloor

  • it’s symmetrical on both sides of the

    • mid-ocean ridge

∴ stripes of rock on the seafloor with alternating magnetic properties

occurs on

How does evidence of magnetic striping support the plate tectonic theory? (1/2)

1) Presence of Basaltic Rocks

• basaltic rocks from the oceanic crust (FYI)

  • are volcanic rocks formed from iron-rich lava

• contains iron-rich magnetic materials

• when the iron-rich lava erupts from the centre of the mid-ocean ridge

  • it cools and solidifies

    → its magnetic materials point towards Earth’s magnetic North

    • recording evidence of Earth’s polarity at that time

How does evidence of magnetic striping support the plate tectonic theory? (2/2)

2) Symmetrical Zebra-Like Magnetic Pattern on both sides of the Mid-Ocean Ridge

• zebra-like pattern is symmetrical on either side of the mid-ocean ridges

  • shows that this is not a random occurrence

∴ supports the plate tectonic theory as it provides evidence that the plates move

• as oceanic plates diverge away from each other

  1) iron-rich lava erupts from the centre of the ridge

  • the lava cools and solidifies

    → forming new oceanic crust

    2) the crust is then pushed in both directions away from the centre of the ridge

    • as the oceanic plates move apart

    3) when Earth’s polarity reverses

    • the rocks record the reversals

    4) over time, a symmetrical zebra-like magnetic pattern forms

    • supporting the fact that plates move during seafloor spreading