Geomagnetic reversal
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During the 1950s-70s, scientists learned that the ocean seafloor is patterned by stripes of magnetism, with alternating sections magnetized north, south, north, etc.<ref name="About">[http://geography.about.com/od/physicalgeography/a/magnetic.htm Rosenberg, Matt. "Magnetic Reversal." About.com. n.d. Web. 05 June 2014.]</ref><ref name="NOAA">[http://www.oceanexplorer.noaa.gov/edu/learning/2_midocean_ridges/activities/seafloor_spreading.html "Seafloor Spreading Activity." NOAA. 12 February 2013. Web. 28 June 2014.]</ref><ref name="CD741">[http://www.talkorigins.org/indexcc/CD/CD741.html Isaac, Mark. "Claim CD741." Talk.Origins Archive. 13 February 2004. Web. 28 June 2014.]</ref> | During the 1950s-70s, scientists learned that the ocean seafloor is patterned by stripes of magnetism, with alternating sections magnetized north, south, north, etc.<ref name="About">[http://geography.about.com/od/physicalgeography/a/magnetic.htm Rosenberg, Matt. "Magnetic Reversal." About.com. n.d. Web. 05 June 2014.]</ref><ref name="NOAA">[http://www.oceanexplorer.noaa.gov/edu/learning/2_midocean_ridges/activities/seafloor_spreading.html "Seafloor Spreading Activity." NOAA. 12 February 2013. Web. 28 June 2014.]</ref><ref name="CD741">[http://www.talkorigins.org/indexcc/CD/CD741.html Isaac, Mark. "Claim CD741." Talk.Origins Archive. 13 February 2004. Web. 28 June 2014.]</ref> | ||
| − | This occurs because magma contains iron grains (specifically magnetite<ref name="PWN"/>) that orient themselves towards the magnetic north pole, much like a compass. When lava solidifies, the iron grains are no longer able to move freely, and are permanently aligned towards wherever the magnetic north pole was. Thus, when magma from oceanic trenches hardens into seafloor, it will maintain its magnetic alignment.<ref name=" | + | This occurs because magma contains iron grains (specifically magnetite<ref name="PWN"/>) that orient themselves towards the magnetic north pole, much like a compass. When lava solidifies, the iron grains are no longer able to move freely, and are permanently aligned towards wherever the magnetic north pole was. Thus, when magma from oceanic trenches hardens into seafloor, it will maintain its magnetic alignment.<ref name="PWN"/><ref name="About"/><ref name="NOAA"/> |
Interestingly, the ages of magnetic stripes on both sides of the Atlantic Ocean<ref name="About"/><ref name="CD741"/> and all over the world match. This would only occur if all of these locations had experienced the same magnetic field at the same time. | Interestingly, the ages of magnetic stripes on both sides of the Atlantic Ocean<ref name="About"/><ref name="CD741"/> and all over the world match. This would only occur if all of these locations had experienced the same magnetic field at the same time. | ||
Revision as of 17:48, 28 June 2014
- CERN
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- Ghost in the machine
- Global warming conspiracy theory
- Greenhouse effect
- Scientism
“”Magnetism, as you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators.
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| —Dave Barry[1] |
A geomagnetic reversal is a shift in Earth's magnetic field in which the positions of the magnetic north (positive) and south (negative) are switched.[2][3] In modern times, a reversal has usually occured every 50,000 to 800,000 years, with an average of 200,000 years.[2][4]
Contents |
Evidence for
Seafloor Magnetic Stripes
During the 1950s-70s, scientists learned that the ocean seafloor is patterned by stripes of magnetism, with alternating sections magnetized north, south, north, etc.[5][6][7]
This occurs because magma contains iron grains (specifically magnetite[3]) that orient themselves towards the magnetic north pole, much like a compass. When lava solidifies, the iron grains are no longer able to move freely, and are permanently aligned towards wherever the magnetic north pole was. Thus, when magma from oceanic trenches hardens into seafloor, it will maintain its magnetic alignment.[3][5][6]
Interestingly, the ages of magnetic stripes on both sides of the Atlantic Ocean[5][7] and all over the world match. This would only occur if all of these locations had experienced the same magnetic field at the same time.
Importance of
Seafloor Spreading
The theory of seafloor spreading (and of continental drift) is supported by the existence of magnetic stripes in the rock of the ocean floor.[6][7]
Around 170-171 reversals are documented.[5][8]
Alternate "interpretations"
Strength fluctuations
Walt Brown[7]
Constant Decline
Some creationists, especially earlier ones such as Thomas Barnes[9], argue against the occurrence of geomagnetic reversals, and instead believe that the magnetic field of the earth is continually in decline. The major problem with this theory is the assumption that current geomagnetic decay rates are the same as thousands of years ago, when there is significant evidence against this. The geomagnetic field frequently changes strength, especially during geomagnetic reversals. In fact, during the most recent geomagnetic reversal the Earth's magnetic field reduced to 5% of its original strength.[10] The earth's geomagnetic field appears to be currently undergoing a geomagnetic reversal, which would account for the continuous decrease of the strength of the earth's geomagnetic field.[5]
Further, as Brent Dalrymple states, "The dynamo theory has gained near-universal acceptance because it is the only proposed mechanism that can explain all the observed features of the Earth's magnetic field. In contrast, Barnes' hypothesis of a freely decaying field cannot explain the existence, configuration, movement, or changes in the nondipole field, the fluctuations in the dipole moment, the reversals in field polarity, or the documentation in the geologic record of the continued existence of the field for more than three billion years."[11]
Goddidit
Later creationists, such as Russell Humphreys[9], generally accepted that geomagnetic reversals occurred.
Rapid Reversal
Apocalyptic
Robert W. Felix and Alan Caruba
Stolen Stuff
Talk.Origins
The shape of the dipole field is not ideal but is highly distorted by irregularities superimposed on the dipole field. These irregularities, collectively called the nondipole field, are thought to be caused by eddy currents in the liquid core at the Earth’s core/mantle boundary. Like the dipole field, the nondipole field is slowly and constantly changing. The Earth’s magnetic field we actually observe at any spot on the Earth is the sum of dipole and nondipole fields.
Quote from Scientists Confront Creationism
"We do not need to assume that the drifting of the continents has been at a constant rate over the past 200 million years, for we have a magnetic record of their movements. The molten rock that oozes up in the Mid-Atlantic Ridge is partly magnetized by the magnetic field of the earth, and as the rock cools that magnetism is frozen into it. We can measure the magnetic polarity of the rocks in the sea floor with delicate magnetometers towed on the ocean surface. This would, of course, not be interesting if it were not that the magnetic field of the earth reverses itself every half million or so years; in fact, in the past 76 million years, it has reversed itself 171 times. Ocean floor rocks close to the Mid-Atlantic Ridge carry the magnetism of the present field, but those several miles away on either side have the reversed magnetic polarity of the field of the earth half a million years ago, and those still farther have the polarity of the still earlier field, and so on. Over recent geological times the alternating polarity of the magnetism in the ocean for has reversed many times in consort with the changing field of the earth. Moreover, this patter of field reversals is consistently reproduced in the ocean floor in widely separated regions of the earth. But how do we know the dates of the magnetic field reversals in the ocean floor? The age of any reversal can be estimated by extrapolation along the sea-floor magnetic strips, assuming constant spreading rates, once a reliable chronology is constructed for a portion of the strip. Such a reliable chronology has been constructed for the most recent segment - up to 5 million years ago. It is based on direct radioactive dating of sequences of lava flows."
External links
Google Books: Reversals of the Earth's Magnetic Field Our Magnetic Earth
Other: [1] [2] [3] [4] [5] [6] [7] [8] [9]\ [10] [11] [12] [13] [14] [15] [16]
Images to Use
http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/ocean_age.gif
See also
Creationist pseudoscience:
References
- ↑ "Magnetism, as you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators." Just-One-Liners.com. n.d. Web. 04 June 2014.
- ↑ 2.0 2.1 "Reversals: Magnetic Flip." Natural Environment Research Council. n.d. Web. 04 June 2014.
- ↑ 3.0 3.1 3.2 "Magnetic Striping." Prince William Network. n.d. Web. 28 June 2014.
- ↑ Roach, John. "Earth's Magnetic Field Is Fading." National Geographic Society. 09 September 2004. Web. 04 June 2014.
- ↑ 5.0 5.1 5.2 5.3 5.4 Rosenberg, Matt. "Magnetic Reversal." About.com. n.d. Web. 05 June 2014.
- ↑ 6.0 6.1 6.2 "Seafloor Spreading Activity." NOAA. 12 February 2013. Web. 28 June 2014.
- ↑ 7.0 7.1 7.2 7.3 Isaac, Mark. "Claim CD741." Talk.Origins Archive. 13 February 2004. Web. 28 June 2014.
- ↑ Laurie R. Godfrey (1983). "Scientists Confront Creationism". W. W. Norton & Company, Canada. Pages 36-37. ISBN 0393301540.
- ↑ 9.0 9.1 Major, Trevor. "The Earth's Young Magnetic Field." Apologetics Press. 1993. Web. 04 June 2014.
- ↑ "Ice age polarity reversal was global event: Extremely brief reversal of geomagnetic field, climate variability, and super volcano." Helmholtz Centre Potsdam. 16 October 2012. Web. 04 June 2014.
- ↑ 1992. "Can Earth be Dated from Decay of its Magnetic Field?" NCSE Reports, Vol.12, No.1 (Spring 1992), pp.16-17 National Center for Science Education, P.O. Box 9477, Berkeley, CA 94709-0477.