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How do marine magnetic stripes provide evidence for seafloor spreading?

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Earth's lithosphere and upper mantle — oceanic crust A cross section of Earth's outer layers, from the crust through the lower mantle.

Marine magnetic stripes provide critical evidence for seafloor spreading by acting as a chronological record of Earth’s magnetic field reversals.12

The theory, developed by Frederick J. Vine, Drummond H. Matthews, and Lawrence W. Morley, relies on three key principles:
* Geomagnetic Reversals: Earth’s magnetic field periodically reverses its polarity.12
* Permanent Magnetization: As new oceanic crust forms at spreading centres, iron-titanium minerals in the cooling lava lock in the magnetic orientation of the field at that time.12
* Bilateral Symmetry: As new crust is created, it splits and moves away from the ridge. This process generates a symmetrical pattern of "positive" (normal polarity) and "negative" (reversed polarity) magnetic stripes on both sides of the ridge.12

Because these stripes parallel the ridge and correlate with known magnetic polarity-reversal timescales, they confirm that the seafloor is continuously moving away from spreading centres, allowing scientists to calculate the rate of crustal movement.12