Figure 9-22: Magnetic Stripes on the Ocean Seafloor Magnetic measurements, illustrated here, clearly show that the seafloor preserves a record of past magnetic field reversals. New material is magnetized as it comes up at the mid-ocean rift and solidifies into the crust. Then, the newly magnetized crust is carried away by seafloor spreading as freshly solidified material repeats this process at the rift. Over millions of years, Earth’s magnetic field flips several times, leaving stripes of alternating field directions in the seafloor. For simplicity, the magnetic field is drawn pointing up or down, but the actual direction depends on the latitude of the rift.