How do magnetic stripes of iron in ocean rock provide evidence of seafloor spreading?

Question

They show when Earth's poles reversed.
They show how the density of the seafloor has changed.
They reveal a matching pattern on either side of the ridge.
They reveal differences in the mineral composition of newly created rock.

Answer 1

The correct answer is:

They reveal a matching pattern on either side of the ridge.

Magnetic stripes of iron in ocean rock are created as magma rises at mid-ocean ridges and solidifies into new oceanic crust. As magma cools, iron minerals within the rock align with the Earth's magnetic field. Because the Earth's magnetic field has flipped (reversed) many times throughout geological history, the resulting magnetic orientation of the rocks creates a pattern of stripes that can be observed. These stripes serve as a record of the history of magnetic field reversals and create a symmetrical pattern on either side of the mid-ocean ridges. This matching pattern provides evidence of seafloor spreading—indicating that new crust is continuously formed at the ridge and pushes older crust away from it.