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The duration of a full reversal varies between 2,000 and 12,000 years. [3] Although there have been periods in which the field reversed globally (such as the Laschamp excursion) for several hundred years, [4] these events are classified as excursions rather than full geomagnetic reversals. Stable polarity chrons often show large, rapid ...
The following is a list of geomagnetic reversals, showing the ages of the beginning and end of each period of normal polarity (where the polarity matches the current direction). Source for the last 83 million years: Cande and Kent, 1995. [1] Ages are in million years before present (mya).
The polarity of the Earth's magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetism to track the past motion of continents.
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth's magnetic field.Unlike reversals, an excursion is not a long-term re-orientation of the large-scale field, but rather represents a dramatic, typically a (geologically) short-lived change in field intensity, with a variation in pole orientation of up to 45° from the previous position.
The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. Evidence from paleomagnetism led to the revival of the continental drift hypothesis and its transformation into the modern theory of plate tectonics.
A polarity chron, or in context chron, [4] is the time interval between polarity reversals of Earth's magnetic field. [5] It is the time interval represented by a magnetostratigraphic polarity unit. It represents a certain time period in geologic history where the Earth's magnetic field was in predominantly a "normal" or "reversed" position.
Magnetic field reversal may refer to: Geomagnetic reversal. Brunhes–Matuyama reversal, approximately 780,000 years ago; Gauss-Matuyama reversal, approximately 2.588 million years ago; Jaramillo reversal, approximately one million years ago; Laschamp event, a short reversal that occurred 41,000 years ago; Reversal of the solar magnetic field
Media in category "Geomagnetic reversal" This category contains only the following file. Geomagnetic polarity 0-169 Ma.svg 300 × 1,800; 18 KB