Paleomagnetic dating relies on

The time between reversals has ranged between less than 100,000 to tens of millions of years with an average of about 300,000 years. It takes 1,000-8,000 years for one to be completed. It is thought that as a reversal approaches, the earth's magnetic field weakens.It has been gradually weakening for the last 250 years.

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

New oceanic crust is magnetized as it forms and then it moves away from the ridge in both directions.

Before clay is fired and while lava is still in a molten state, the very weak magnetic fields of individual particles are randomly oriented. Later, its thermoremnant magnetism is measured with a magnetometer.

By comparing these data, a researcher can determine the direction of magnetic north at the last time the sample had been exposed to a high temperature..

These include biomagnetism, magnetic fabrics (used as strain indicators in rocks and soils), and environmental magnetism.

As early as the 18th century, it was noticed that compass needles deviated near strongly magnetized outcrops.

That may mean that another reversal is coming, but not for a few thousand years.

The earth's magnetic field helps block out dangerous ionizing radiation from our sun.

The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool.

Geophysicists who specialize in paleomagnetism are called paleomagnetists.

A compass needle would have pointed to the south pole during some periods and to the north pole during others.

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