How can we use rock to tell the Earth’s magnetic field has shifted over the eons?

It’s a chronological index. Temporal patterns of the Earth’s magnetic flux influence orientations of magnetic material spewed from magma. The metallic atoms of this lava are liquid-like when they come out and align to the Earth’s current field then solidify, never changing polarity again. When analysed with magnetic devices the indication can be noted.

1 Comment

  1. I’ve been looking at this topic lately, but nowhere did I find a simple statement about how we know this. Thanks for posting it


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