Geomagnetic reversals

From CreationWiki, the encyclopedia of creation science

It has been theorized that new oceanic crust has formed at the crest of the mid-oceanic ridge inducing spreading of the sea floor and continental drift.

Beginning in the 1950s, scientists began recognizing odd magnetic variations across the ocean floor. The iron-rich basalt (volcanic rock) making up the ocean floor contains a magnetic mineral (magnetite), and can locally distort compass readings. This distortion was recognized by Icelandic mariners as early as the late 18th century. Because the presence of magnetite gives the basalt measurable magnetic properties, these magnetic variations provided another means to study the deep ocean floor. As more and more of the seafloor was mapped, the magnetic variations turned out not to be random or isolated occurrences, but instead revealed recognizable patterns.

The deep ocean floor showing the magnetic striping mapped by oceanographic surveys offshore of the Pacific Northwest. Thin black lines show transform faults that offset the striping.

Magnetic readings of sea floor rocks has found them to generally belong to two groups. One group has the same polarity as that of the Earth's present magnetic field. The other group has reversed polarity. When these magnetic properties of sea floor rocks were mapped over a wide region, a repeating pattern was evident. Alternating stripes of magnetically different rock were found in rows on either side of the mid-oceanic ridge: one stripe with normal polarity and the adjoining stripe with reversed polarity. The overall pattern, defined by these alternating bands of normally and reversely polarized rock, became known as magnetic striping.

It is believed that the unusual magnetic orientation pattern of sea floor rocks is due to repeated reversals of the Earth's magnetic field when the rocks were cooling from molten material. According to this model, the magnetite grains in the magma (molten rock) will align themselves with the orientation of the Earth's magnetic field while in a fluid state. When magma cools, the alignment of the magnetite grains is fixed, effectively recording the Earth's magnetic orientation or polarity (normal or reversed) at the time of cooling.

If this interpretation of magnetic striping is correct, the striped pattern of sea floor rocks offers support for the theory of continental drift, which many creationists believe occurred as a result of catastrophic plate tectonics during the Biblical flood of Noah. Radiometric dating of sea floor rocks using potassium-argon dating method has also revealed a correlation between the distance of the rocks from the mid-oceanic ridge and the quantity of unstable isotopes in the sample. [1]