When new rock is added to an oceanic ridge, the magnetized strips on either side of the ridge are evidence of sea-floor spreading. this is because the rocks on the two sides of the ridge

The rocks on the two sides of the ridge move outward.

Spread away on both sides and get aligned with the magnetic properties of the earth.

Explanation:

Harry Hess in his seafloor spreading theory has stated that the seafloor spreads at a continuous rate and that newer crust is fired by the recycling of the older crust form below and the upwelling of lavas or magmas at this mid-oceanic ridges this leads to the formation of the two distinct types of rocks with opposite magnetic properties. Moving away from the rides we find the older rocks and moving closer we find newer rocks or slabs.

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