Palaeomagnetism Flashcards
What is every palaeomagnetism?
The study of the history of the Earth’s magnetic field
What happens every 200,000 years to the Earth’s magnetic polarity?
It reverses polarity (magnetic north and south poles switch)
What has palaeomagnetism provided evidence for?
The process of sea floor spreading
What happens as magma erupts from mid-ocean ridges?
The magnetic minerals in the molten rock align themselves with the direction of the Earth’s magnetic field
What happens to the magnetic alignment when the crust solidifies?
The alignment becomes fixed
What is the difference between magnetic minerals aligned in periods of normal polarity and reverse polarity?
Normal polarity - magnetic minerals are aligned magnetic north near the North Pole
Reverse polarity - magnetic minerals are aligned magnetic north near the South Pole
Magnetic minerals are aligned in opposite directions to each other
What does palaeomagnetism result in?
A series of alternating magnetic stripes along the sea floor.
What do the strips on the sea floor show?
The crust is older the further away from a mid-ocean ridge you go - so the plates are moving apart
