Magnetic Reversals And Seafloor Spreading

Magnetic stripes are the result of reversals of the earth s field and seafloor spreading.

Magnetic reversals and seafloor spreading.

Magnetic reversals after molten lava emerges from a volcano it solidifies to a rock. The hypothesis links seafloor spreading and geomagnetic reversals in a powerful manner with each expanding knowledge of the other. The models show a ridge a about 5 million years ago b about 2 to 3 million years ago and c in the present. In 1963 both the geophysicist frederick j.

Magnetic reversal proves seafloor spreading because we can see the polarity of the earth s magnetic field in rocks. This was sufficient to allow computing of spreading rates over the last 700 000 years on many mid ocean. Seafloor spreading and polar reversal. What they discovered was the mid ocean ridge was actually a site where tectonic plates which are large pieces of the earth s crust were pulling apart from.

Early in the history of investigating the hypothesis only a short record of geomagnetic field reversals was available for studies of rocks on land. Basalt the once molten rock that makes up most new oceanic crust is a fairly magnetic substance and scientists began using magnetometers to measure the magnetism of the ocean floor in the 1950s what they discovered was that the magnetism of the ocean floor around. Paleomagnetism or palaeomagnetism in the united kingdom is the study of the record of the. Morley independently realized that if the seafloor spreading theory was correct then the rocks surrounding mid oceanic ridges should show symmetric patterns of magnetization reversals recording the changes of the earth s magnetic field in the volcanic rocks at the.

The magnetism of mid ocean ridges helped scientists first identify the process of seafloor spreading in the early 20th century. As magma cools particles in it get frozen in the direction of the. Its magnetization is in the direction of the local magnetic force at the time when it cools down. Figure 5 magnetic reversals in oceanic crust are shown as bands of light blue and dark blue oceanic crust.

In most cases it is a black rock known as basalt which is faintly magnetic like iron emerging from a melt for which gilbert already noticed a similar process. New oceanic crust is magnetized as it forms and then it moves away from the ridge in both directions.