alternating
Earth's magnetic field has reversed itself many times over its history, as evidenced by the alignment of iron minerals in rocks that record these changes. This phenomenon is known as geomagnetic reversal, where the magnetic north and south poles switch places.
Paleomagnetism is the study of ancient magnetic fields recorded in rocks. By analyzing the orientation of magnetic minerals in rocks, scientists can determine the past positions of continents and the movement of tectonic plates over time. This information supports the theory of plate tectonics by providing evidence of continental drift and plate movement.
Rocks along the central valley of the mid-ocean ridge show a pattern of alternating polarity, indicating reversals in Earth's magnetic field. This pattern is caused by the cooling of magma at the ridge, locking in the magnetic orientation at the time of solidification. By studying the magnetic properties of these rocks, scientists can determine the rate of sea-floor spreading and the age of the oceanic crust.
They are arranged in a pattern with magnetic strips having reversed polarities.
Periodically, the magnetic field of the earth reverses polarity. The direction of the magnetic field is recorded in the magnetic properties of rocks when they are erupted. Rocks are being continuously added at sea floor spreading regions, and thus the magnetic reversals are recorded as pairs of parallel 'stripes' alongside the mid ocean spreading ridge.
Evidence that Earth's magnetic field changes can be found in the alignment of magnetic minerals in rocks on the ocean floor. As magma solidifies into new rock, the magnetic minerals within it align with the current magnetic field direction. By studying the alignment of these minerals in rocks of different ages along the ocean floor, scientists can track changes in the Earth's magnetic field over time.
its the same on either side of the mid-ocean ridge
Iron-rich rocks can exhibit both normal and reversed magnetic polarity. When these rocks cool and solidify, the minerals containing iron align with the Earth's magnetic field. Over time, the Earth's magnetic field can reverse, causing the mineral alignment to also reverse, resulting in rocks with reversed polarity.
Iron minerals that are present in magma or lava along the ridge that has not completely crystallized into rock are aligned with the Earth's polarity. When the magma or lava cools and solidifies completely, the magnetic orientation of the Earth at that time is preserved in the body of igneous rock.
because the scientists found that the farther the rocks the older the rocks were. so the youngest rocks were found near the mid-ocean ridge. this showed that sea-floor spreading took place. +++ The primary evidence is "magnetic striping": remnant magnetising by the Earth's magnetic field of the iron compounds in the basalt forming the ocean floor. The magnetic traces are parallel to the spreading-ridges, and their polarity reflect the field's periodic reversal. The further from the ridge, the older the stripes. The rock is imprinted with the magnetism as it cools below a certain point in being eruped along the ridge.
as you move away from an ocean ridge the rocks get older
A mid-ocean ridge would have magnetic striping on the seafloor. This striping is caused by the alternating polarities of Earth's magnetic field recorded in the basaltic rocks as they cool and solidify at the mid-ocean ridge, providing evidence for seafloor spreading.