Magnetic strips appear on the seafloor because it spreads apart, forming new rocks that have a magnetic properties.
New oceanic crust is being created at the mid-ocean rift zones, a global divergent plate boundary system where uprising magma fills in the spaces being created by the pulling apart of plates. Part of the newly forming crust follows the direction of one plate, and part of the newly forming crust follows the direction of the other plate; therefore, the age of the rock created from the magma has a mirror image on either side of the rift.
As new oceanic crust is continuously being formed at the mid-ocean ridges by upwelling molten rock, the direction of Earth's magnetic field is recorded in the rock by the orientation of magnetic minerals, which align themselves in the direction of the magnetic field before the rock completely crystallizes.
Earth's magnetic field is known to change its orientation with frequency on a geologic time scale, thus a pattern of stripes of magnetic orientation is formed which can be detected with a magnetometer.
The discovery of magnetic stripes on the seafloor have allowed researchers to provide additional proof that new crust is being created, and that magnetic reversals have occurred and will occur in the future.
They tell us that over the course of thousands of years, Earth's polarity will reverse itself. The stripes are the magnetic "footprint" of Earth's shifting magnetic field.
The seafloor spreads apart, creating new rocks that record magnetic orientation.
pole reversal millions of years apart
Pole reversal
They proved that the seafloor was spreading.
Magnetic alignment of rocks, in alternating strips that run parallel to ridges, indicates reversals in Earth's magnetic field and provides further evidence of seafloor spreading.
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The seafloor spreads apart, creating new rocks that record magnetic orientation. Small grains of magnetite on the volcanic basalt (ocean floor) have magnetic properties.
parrell strips of igneous rocks on each side of the ridge show matching reversal of magnetic polity
They proved that the seafloor was spreading.
Magnetic alignment of rocks, in alternating strips that run parallel to ridges, indicates reversals in Earth's magnetic field and provides further evidence of seafloor spreading.
The Pacific seafloor formed at a faster spreading rate than the Atlantic seafloor.
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The seafloor spreads apart, creating new rocks that record magnetic orientation. Small grains of magnetite on the volcanic basalt (ocean floor) have magnetic properties.
The seafloor spreads apart, creating new rocks that record magnetic orientation. Small grains of magnetite on the volcanic basalt (ocean floor) have magnetic properties.
large regions of the seafloor that appear flat but are not
parrell strips of igneous rocks on each side of the ridge show matching reversal of magnetic polity
Lawrence W. Morley, Frederick John Vine, and Drummond Hoyle Matthews were the first to tie magnetic stripe anomalies to seafloor spreading. The magnetic anomalies was the first evidence that supported the theory of seafloor spreading.
When Earth's magnetic poles have reversed themselves.
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