Form the basis of paleomagnetic dating Video sexchatroulette

could be tested by ascertaining the magnetic characteristics of ancient rocks; however, it was not until after World War II that rock paleomagnetism data was gathered.Paleomagnetism is possible because some of the minerals that make up rocks—notably magnetite—become permanently magnetized parallel to the earth's magnetic field at the time of their formation.This means that the pattern of normal and reverse polarity in an assemblage of rocks can be distinctive in the same way (though for a completely different reason) that growth rings in a tree can be distinctive.We might, for example, see a long period of reverse polarity, followed by six very quick switches of polarity, followed by a long period of normal polarity; and this might be the only time that such a thing occurs in our timeline.You can image how such a radical theory would have been met with much ridicule from the scientific community, especially at the time of its proposal back in the early part of the 20th century.In fact, Wegener's ideas continued to be debated for decades following his death in 1930.Rocks from hot liquid magma (see lava), or even minerals made up of crystals that grow at low temperatures, can acquire magnetization.Also, when magnetized minerals become disaggregated from their parent rocks by erosion and are carried into a basin, they will tend to align themselves parallel to the earth's magnetic field as they settle in still water.

So, you can sympathize with how the German meteorologist, Alfred Wegener, must have felt when he proposed his theory called continental drift, in which he hypothesized that at one time all of the continents were joined and then slowly drifted apart.Periods of "normal" polarity (i.e., when the north-seeking end of the compass needle points toward the present north magnetic pole, as it does today) have alternated with periods of "reversed" polarity (when the north-seeking end of the compass needle points southward).The cause of these magnetic "flip-flops" is not clearly understood.This process, in which the rotation of a planet with an iron core produces a magnetic field, is called a dynamo effect.The Earth's magnetic core is generally inclined at an 11 degree angle from the Earth's axis of rotation.

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