317:, where satellites and power supplies may be damaged, although compass navigation would also be affected. Some forms of life that are thought to navigate based on magnetic fields may be disrupted, but again it is suggested that these species have survived excursions in the past. Since excursion periods are not always global, any effect might well only be experienced in certain places, with others relatively unaffected. The time period involved could be as little as a century, or as much as
226:
339:
Recent analysis of the geomagnetic reversal frequency, oxygen isotope record, and tectonic plate subduction rate, which are indicators of the changes in the heat flux at the core mantle boundary, climate and plate tectonic activity, shows that all these changes indicate similar rhythms on million
146:
suggests that excursions occur when the magnetic field is reversed only within the liquid outer core; reversals occur when the inner core is also affected. This fits well with observations of events within the current chron of reversals taking 3,000–7,000 years to complete, while excursions
64:
Except for recent periods of the geologic past, it is not well known how frequently geomagnetic excursions occur. Unlike geomagnetic reversals, which are easily detected by the change in field direction, the relatively short-lived excursions can be easily overlooked in long duration, coarsely
55:
are generally not recorded around the entire globe. This is certainly due in part to them not registering well in the sedimentary record, but it also seems likely that excursions may not typically extend through the entire global geomagnetic field. There are significant exceptions, however.
114:
The most popular hypothesis is that they are an inherent aspect of the dynamo processes that maintain the Earth's magnetic field. In computer simulations, it is observed that magnetic field lines can sometimes become tangled and disorganized through the chaotic motions of
164:, is that geomagnetic excursions are not spontaneous processes but rather triggered by external events which directly disrupt the flow in the Earth's core. Such processes may include the arrival of continental slabs carried down into the
147:
typically last 500–3,000 years. However, this timescale does not hold true for all events, and the need for separate generation of fields has been contested, since the changes can be spontaneously generated in mathematical models.
418:
decays more rapidly with the distance from the source – in this case the Earth's core. The magnetic field then expressed at the surface of the Earth would be considerably less intense, even without significant changes in its
208:
and mantle. If the sea-level change is sufficiently large (>10 meters) and rapid (in a few hundred years), then the velocity shear in the liquid core disrupts the convective cells that drive the Earth's dynamo.
65:
resolved, records of past geomagnetic field intensity. Present knowledge suggests that they are around ten times more abundant than reversals, with up to 12 excursions documented within the current reversal period
188:. Supporters of this theory hold that any of these events lead to a large scale disruption of the dynamo, effectively turning off the geomagnetic field for a period of time necessary for it to recover.
406:
Under the "disorganized dynamo" scenario, the Earth's internal magnetic field intensity does not significantly change within the core itself, but rather, its energy is transferred from the ordinary
134:). However, the equivalent process in the sun invariably leads to a reversal of the solar magnetic field: It has never been observed to recover without a full-scale change in its orientation.
75:
Geomagnetic excursions in the
Matuyama, Gauss and Gilbert chrons are also reported and new possible excursions are suggested for these chrons based on analysis of the deep drilling cores from
393:
did in fact involve a few hundred years when the magnetic poles were completely reversed; later discoveries showed that the reversed field was only 5% of its "normal" strength. Since the
45:
Excursion events typically only last a few thousand to a few tens of thousands of years, and often involve declines in field strength to between 0 and 20% of normal. Unlike full
605:
Kravchinsky, V.A. (2017). "Magnetostratigraphy of the Lake Baikal sediments: A unique record of 8.4 Ma of continuous sedimentation in the continental environment".
704:
Rampino, Michael R. (1979). "Possible relationships between changes in global ice volume, geomagnetic excursions, and the eccentricity of the Earth's orbit".
332:
There is evidence that geomagnetic excursions are associated with episodes of rapid short-term climatic cooling during periods of continental glaciation (
282:
Due to the weakening of the magnetic field, particularly during the transition period, greater amounts of radiation would be able to reach the
98:
processes that generates the magnetic field. Others suggest that excursions occur when the magnetic field is reversed only within the liquid
294:. However, it is likely that nothing serious would occur, as the human species has certainly lived through at least one such event;
494:"Ice age polarity reversal was global event: Extremely brief reversal of geomagnetic field, climate variability, and super volcano"
119:
in the Earth's core. In such cases, this spontaneous disorganization can cause decreases in the magnetic field as perceived at the
826:
340:
years' timescale in the
Cenozoic Era occurring with the common fundamental periodicity of ~13 Myr during most of the time.
94:
is divided on what causes geomagnetic excursions. The dominant hypothesis is that they are an inherent instability of the
310:
with no known ill effect, and excursions are shorter-lived and do not result in permanent changes to the magnetic field.
196:
Richard A. Muller and Donald E. Morris suggest geomagnetic reversal due to very large impact event and following rapid
42:) short-lived change in field intensity, with a variation in pole orientation of up to 45° from the previous position.
456:
397:
has also been seen in sites around the Earth, it is suggested as one of the few examples of a truly global excursion.
269:
251:
683:
389: years ago. Although it is thought that many excursions only affect the field over a part of the globe, the
236:
779:"The Laschamp-Mono lake geomagnetic events and the extinction of Neanderthal: A causal link or a coincidence?"
851:
725:
527:"Paleointensity of the Earth's magnetic field during the Laschamp excursion and its geomagnetic implications"
307:
66:
38:
is not a "permanent" re-orientation of the large-scale field, but rather represents a dramatic, typically a (
349:
27:
811:
181:
493:
247:
739:
Chen, J.; Kravchinsky, V.A.; Liu, X. (2015). "The 13 million year
Cenozoic pulse of the Earth".
684:"An extremely brief reversal of the geomagnetic field, climate variability and a super volcano"
243:
103:
99:
752:
542:
790:
748:
713:
656:
614:
577:
538:
465:
302:
46:
22:
8:
359:
120:
794:
717:
660:
618:
581:
469:
72:
Geomagnetic excursions for the
Brunhes geomagnetic chron are relatively well described.
126:
This scenario is supported by observed tangling and spontaneous disorganization in the
91:
822:
640:
550:
478:
451:
314:
161:
802:
626:
313:
The major hazard to modern society is likely to be similar to those associated with
184:, and possibly mantle-core shear forces and displacements resulting from very large
798:
756:
721:
664:
622:
585:
546:
473:
415:
411:
205:
165:
173:
169:
39:
681:
526:
821:. Vol. 5 Geomagnetism (1st ed.). Elsevier Science. pp. 373–416.
760:
420:
394:
390:
379:
197:
845:
501:
204:
and change of water redistribution more to poles alters the rotation rate of
143:
95:
668:
296:
287:
185:
177:
116:
590:
565:
354:
131:
76:
291:
682:
Helmholtz
Association of German Research Centres (16 October 2012).
644:
254:. Statements consisting only of original research should be removed.
778:
333:
201:
407:
452:"The distinction between geomagnetic excursions and reversals"
137:
283:
80:
79:
and their comparison with the oceanic core (ODP) and
Chinese
127:
726:
10.1130/0091-7613(1979)7<584:PRBCIG>2.0.CO;2
102:, and complete reversals would occur when the outer and
776:
524:
520:
518:
738:
645:"Geomagnetic Reversals from Impacts on the Earth"
109:
843:
515:
486:
445:
443:
441:
439:
777:Valet, Jean-Pierre; Valladas, Hélène (2010).
566:"Geomagnetic excursions: Knowns and unknowns"
525:Roperch, P.; Bonhommet, N.; Levi, S. (1988).
150:
639:
378:One of the first excursions studied was the
191:
160:A minority opinion, held by such figures as
809:
604:
436:
138:Outer-core inner-core opposition hypothesis
327:
589:
477:
270:Learn how and when to remove this message
810:Laj, C.; Channell, J.E.T. (2007-09-27).
155:
703:
563:
449:
130:magnetic field (the 22 or 11 year
844:
643:; Morris, Donald E. (November 1986).
219:
741:Earth and Planetary Science Letters
531:Earth and Planetary Science Letters
13:
86:
14:
863:
770:
457:Geophysical Journal International
26:, is a significant change in the
479:10.1046/j.1365-246X.1999.00810.x
224:
200:. The impact triggered a little
803:10.1016/j.quascirev.2010.09.010
732:
697:
627:10.1016/j.gloplacha.2017.04.002
110:Disorganized dynamo hypothesis
675:
633:
598:
557:
410:configuration to higher order
400:
372:
1:
817:. In Schubert, Gerald (ed.).
812:"5.10 Geomagnetic Excursions"
430:
59:
649:Geophysical Research Letters
570:Geophysical Research Letters
551:10.1016/0012-821X(88)90058-1
350:March 1989 geomagnetic storm
7:
607:Global and Planetary Change
343:
286:, increasing production of
250:the claims made and adding
10:
868:
783:Quaternary Science Reviews
761:10.1016/j.epsl.2015.09.033
414:. The field external to a
215:
151:External driver hypothesis
837:– via elsevier.com.
308:Brunhes–Matuyama reversal
192:Substantial cosmic impact
67:Brunhes–Matuyama reversal
412:multipole configurations
365:
176:, the initiation of new
753:2015E&PSL.431..256C
669:10.1029/gl013i011p01177
543:1988E&PSL..88..209R
450:Gubbins, David (1999).
328:Relationship to climate
819:Treatise on Geophysics
564:Roberts, A.P. (2008).
28:Earth's magnetic field
156:Plate tectonic-driven
18:geomagnetic excursion
852:Geomagnetic reversal
789:(27–28): 3887–3893.
591:10.1029/2008GL034719
303:Homo heidelbergensis
182:core–mantle boundary
23:geomagnetic reversal
795:2010QSRv...29.3887V
718:1979Geo.....7..584R
661:1986GeoRL..13.1177M
619:2017GPC...152..209K
582:2008GeoRL..3517307R
470:1999GeoJI.137....1C
360:Solar storm of 1859
106:are both affected.
641:Muller, Richard A.
382:, dated at around
315:geomagnetic storms
306:lived through the
235:possibly contains
92:Scientific opinion
828:978-0-444-51928-3
423:deep in the core.
280:
279:
272:
237:original research
168:by the action of
162:Richard A. Muller
859:
838:
836:
835:
816:
806:
765:
764:
736:
730:
729:
701:
695:
694:
692:
690:
679:
673:
672:
655:(1): 1177–1180.
637:
631:
630:
602:
596:
595:
593:
561:
555:
554:
537:(1–2): 209–219.
522:
513:
512:
510:
509:
498:Sciencedaily.com
490:
484:
483:
481:
447:
424:
404:
398:
388:
387:
376:
323:
322:
275:
268:
264:
261:
255:
252:inline citations
228:
227:
220:
174:subduction zones
867:
866:
862:
861:
860:
858:
857:
856:
842:
841:
833:
831:
829:
814:
773:
768:
737:
733:
712:(12): 584–587.
702:
698:
688:
686:
680:
676:
638:
634:
603:
599:
562:
558:
523:
516:
507:
505:
492:
491:
487:
448:
437:
433:
428:
427:
405:
401:
385:
383:
377:
373:
368:
346:
330:
320:
318:
276:
265:
259:
256:
241:
229:
225:
218:
212:
194:
170:plate tectonics
158:
153:
140:
121:Earth's surface
112:
89:
87:Possible causes
62:
12:
11:
5:
865:
855:
854:
840:
839:
827:
807:
772:
771:External links
769:
767:
766:
731:
696:
674:
632:
597:
556:
514:
485:
434:
432:
429:
426:
425:
421:field strength
399:
395:Laschamp event
391:Laschamp event
380:Laschamp event
370:
369:
367:
364:
363:
362:
357:
352:
345:
342:
329:
326:
290:and levels of
278:
277:
232:
230:
223:
217:
214:
198:climate change
193:
190:
157:
154:
152:
149:
139:
136:
111:
108:
88:
85:
61:
58:
9:
6:
4:
3:
2:
864:
853:
850:
849:
847:
830:
824:
820:
813:
808:
804:
800:
796:
792:
788:
784:
780:
775:
774:
762:
758:
754:
750:
746:
742:
735:
727:
723:
719:
715:
711:
707:
700:
685:
678:
670:
666:
662:
658:
654:
650:
646:
642:
636:
628:
624:
620:
616:
612:
608:
601:
592:
587:
583:
579:
575:
571:
567:
560:
552:
548:
544:
540:
536:
532:
528:
521:
519:
503:
502:Science Daily
499:
495:
489:
480:
475:
471:
467:
463:
459:
458:
453:
446:
444:
442:
440:
435:
422:
417:
413:
409:
403:
396:
392:
381:
375:
371:
361:
358:
356:
353:
351:
348:
347:
341:
337:
335:
325:
316:
311:
309:
305:
304:
300:and possibly
299:
298:
293:
289:
285:
274:
271:
263:
253:
249:
245:
239:
238:
233:This section
231:
222:
221:
213:
210:
207:
203:
199:
189:
187:
186:impact events
183:
179:
178:mantle plumes
175:
171:
167:
163:
148:
145:
144:David Gubbins
135:
133:
129:
124:
122:
118:
107:
105:
101:
97:
93:
84:
82:
78:
73:
70:
68:
57:
54:
50:
49:
43:
41:
37:
33:
29:
25:
24:
19:
832:. Retrieved
818:
786:
782:
744:
740:
734:
709:
705:
699:
687:. Retrieved
677:
652:
648:
635:
610:
606:
600:
573:
569:
559:
534:
530:
506:. Retrieved
504:. 2012-10-16
497:
488:
464:(1): F1–F4.
461:
455:
402:
374:
338:
331:
312:
301:
297:Homo erectus
295:
288:beryllium 10
281:
266:
257:
234:
211:
195:
159:
142:The work of
141:
125:
117:liquid metal
113:
90:
74:
71:
63:
52:
47:
44:
40:geologically
35:
31:
21:
17:
15:
747:: 256–263.
613:: 209–226.
355:Polar drift
132:solar cycle
77:Lake Baikal
834:2021-02-18
689:2 November
508:2013-07-28
431:References
260:March 2010
244:improve it
104:inner core
100:outer core
60:Occurrence
53:excursions
416:multipole
292:carbon 14
248:verifying
180:from the
83:records.
48:reversals
36:excursion
32:reversals
30:. Unlike
20:, like a
846:Category
344:See also
334:ice ages
791:Bibcode
749:Bibcode
714:Bibcode
706:Geology
657:Bibcode
615:Bibcode
578:Bibcode
539:Bibcode
466:Bibcode
324:years.
242:Please
216:Effects
202:ice age
825:
576:(17).
408:dipole
166:mantle
96:dynamo
815:(PDF)
366:Notes
284:Earth
206:crust
128:solar
81:loess
34:, an
823:ISBN
691:2014
799:doi
757:doi
745:431
722:doi
665:doi
623:doi
611:152
586:doi
547:doi
474:doi
462:137
386:000
336:).
321:000
246:by
172:at
848::
797:.
787:29
785:.
781:.
755:.
743:.
720:.
708:.
663:.
653:13
651:.
647:.
621:.
609:.
584:.
574:35
572:.
568:.
545:.
535:88
533:.
529:.
517:^
500:.
496:.
472:.
460:.
454:.
438:^
384:40
319:10
123:.
69:.
51:,
16:A
805:.
801::
793::
763:.
759::
751::
728:.
724::
716::
710:7
693:.
671:.
667::
659::
629:.
625::
617::
594:.
588::
580::
553:.
549::
541::
511:.
482:.
476::
468::
273:)
267:(
262:)
258:(
240:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.