When magma flows out of a mid ocean ridge small magnetic minerals in the magma align themselves to point in the direction of the earth s current magnetic north.
Magnetic stripes on the sea floor are created where.
In the 1960s the past record of geomagnetic reversals of earth s magnetic field was noticed by observing magnetic stripe anomalies on the ocean floor.
It does however provide evidence that sea floor spreading occurs and hence is evidence for the theory of plate tectonics.
The patterns reflect the creation and spreading of oceanic crust along the mid oceanic ridges.
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.
Magnetic stripes and isotopic clocks oceanographic exploration in the 1950s led to a much better understanding of the ocean floor.
9 10 this results in broadly evident stripes from which the past magnetic field polarity can be inferred from data gathered with a magnetometer towed on the sea surface or from an aircraft.
These surveys revealed a series of invisible magnetic stripes of normal and reversed polarity in the sea floor like that shown in the figure below.
Magnetic reversals found in the sea floor do not cause continental drift.
What they discovered was that the magnetism of the ocean floor around mid ocean ridges was divided into matching stripes on either side of the.
Basalt forming at the ridge crest picks up the existing magnetic polarity.