Last time I looked, north was that way.Last time I looked, north was that way When volcanic rocks rocks which have been produced from the discharges of volcanic matter, as the various kinds of basalt, trachyte, scoria, obsidian, etc., whether compact, scoriaceous, or vitreous. See also: Volcanic cool, the direction of the earth's ever-shifting magnetic field at that moment becomes frozen into the rocks' atomic structure. Geophysicists have long used this leftover magnetization, called thermoremanent magnetization (TRM), as a tool to trace changes in the earth's magnetic field Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the north pole (see Magnetic North Pole) and the other near the geographic south pole (see Magnetic South Pole). and as a yardstick to measure the drift of the continents. But recent basic tests of TRM are throwing a wrench into the geophysicists' toolbox. Joyce Castro and Laurie Brown of the University of Massachusetts The system includes UMass Amherst, UMass Boston, UMass Dartmouth (affiliated with Cape Cod Community College), UMass Lowell, and the UMass Medical School. It also has an online school called UMassOnline. at Amherst had originally set out to test the theory behind TRM by measuring the remanent rem·a·nence n. The magnetic induction that remains in a material after removal of the magnetizing field. [From Middle English remanent, remaining, from Latin magnetizations in Hawaiian lava flows from 1950 and 1972 and comparing those to the direction of the present magnetic field in Hawaii. Because scientists believe the field changes slowly, Castro and Brown expected all the directions to match within a degree or two. But the lavas turned out to be skewed skewed curve of a usually unimodal distribution with one tail drawn out more than the other and the median will lie above or below the mean. skewed Epidemiology adjective Referring to an asymmetrical distribution of a population or of data by as much as 6 degrees, they report in the December GEOPHYSICAL RESEARCH LETTERS Geophysical Research Letters is a publication of the American Geophysical Union. GRL is the organization's only letters journal. Since its introduction in 1974, GRL has published only short research letters, typically 3-5 pages long, which focus on a specific discipline or . The researchers have yet to pin down the cause of this discrepancy. Some scientists have theorized that the shape of lava flows may affect the TRM, but this phenomenon would only account for a difference of a few degrees, says Brown. One possibility, she says, is that the field has changed rather quickly. To test this possible explanation and others, the researchers next plan to measure the TRM of lava within days of its eruption. |
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