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Magnetic Measurements (3D vector)

Magnetic Measurements (3D vector). Intensity Declination (to N mag pole) (requires oriented sample) Inclination (requires oriented sample) Direction (normal/reversed) can come from intensity or declination. Inclination = f( Φ ) Intensity from 25,000 to 75,000. Now Past IDL. Magnetism.

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Magnetic Measurements (3D vector)

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  1. Magnetic Measurements (3D vector) • Intensity • Declination (to N mag pole) (requires oriented sample) • Inclination (requires oriented sample) • Direction (normal/reversed) can come from intensity or declination Inclination = f(Φ) Intensity from 25,000 to 75,000

  2. Now Past IDL

  3. Magnetism • Curie temperature magnetite about 600º C • Vector quantity, only worry about magnitude for the marine magnetic anomalies, measure by remote sensing. Inclination requires direct sampling. • Magnitude function of latitude, from about 25,000 gammas (nT) at the equator to 70,000 gammas at the poles • Anomalies—departure from expected

  4. Reversals • “Rapid” (< 5000 yr) • About 2-3 per million years (but varies wildly) • Most recent about 780,000 yr • From 30 kyr to about 40 myr long

  5. Change with orientation (spreading direction) Change with lat

  6. Cande & Kent 1995 scale Normal is black Most diagnostic anomalies: • 5 (10-18 Ma) • 12-13 (31-33 Ma) • 21-26 (47-57 Ma) • 31-32 (67-73 Ma)

  7. McElhinny & McFadden, 2000 Normal is black Most diagnostic anomalies: 5 (10-18 Ma) 12-13 (31-33 Ma) 21-26 (47-57 Ma) 31-32 (67-73 Ma)

  8. Eltanin (Wikipedia) • USNS Eltanin (T-AK-270/T-AGOR-8) was an Eltanin-classcargo ship with an ice-breaking hull acquired by the U.S. Navy in 1957 and then operated by the Navy in a non-commissioned status, named after Eltanin, the star in constellation Draco. Her designation was changed to that of an oceanographic research ship in 1962 when she operated in Antarctic waters. • Eltanin was assigned to the National Science Foundation to support the Foundation's Antarctic Research Program with the ship operated by the Military Sea Transportation Service.[1] The ship worked in the Antarctic Ocean becoming the first Antarctic research ship to do so. After two shakedown cruises in the Atlantic Ocean and a positioning cruise with further testing en route, Eltanin operated a total of 52 Antarctic research cruises from July 5, 1962 thru December 29, 1972. Over this time, some 80% of the southern ocean was surveyed, and a total of 400,000 miles traveled. • Some of Eltanin's research cruises collected magnetic profiles of the sea floor that proved to be pivotal evidence in the acceptance of the continental drift theory, by proving the existence of sea floor spreading. These key profiles, which show symmetric bands of alternating magnetic orientation (corresponding to magnetic pole reversals) around various undersea ridges, are known by the ship's name and cruise number (ex. Eltanin-19).

  9. Extras

  10. Full rates

  11. Southern Mid Atlantic Ridge (anomaly numbers)

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