Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Magnetic Reversals

Skip navigational links
Dictionaries: Our Mapping Systems   The USGS and Science Education   USGS Fact Sheets   Topics   Keywords   Data Dictionary   Metadata Dictionary   Computer Terminology   Digital Formats  
InfoBank Terms: Activity ID   activity overview   crew   digital data   formal metadata   lines   metadata   NGDC   port stops   project/theme   region   ship   stations   time   virtual globe   year  
Data Types: bathymetry   biological   geochemical   gravity   ground penetrating radar   imaging   LIDAR   logs   magnetics   metering equipment   navigation   samples   seismic   total station   definitions disclaimer  
Data Formats: ARC coverage   E00   FGDC metadata   gridded/image   imaging   material   scattered/swath   Shapefile   vector/polygon  
Comment: 24:38 - 25:38 (01:00)
Source: Annenberg/CPB Resources - Earth Revealed - 3. Earth's Interior
Keywords: "Scott Bogue", magnetism, "magnetic reversal", "rock coring", "lava flow", "Mojave Desert", paleomagnetism

Our transcription: Scientists generally agree that the Earth's magnetic field reverses itself on the average of once every 500,000 years.
Widespread evidence suggests that the last reversal occurred 700,000 years ago, but there is also some evidence that as many as a dozen reversals may have occurred since that time.
We know that in general terms during a magnetic reversal, the field intensity decreases to 10 or 20 percent of its normal value, so at some point as the Earth were entering a reversal, there would be a decrease in field intensity.
We know by comparing the magnetic field strength today to measurements of the magnetic field 160 years ago that the Earth's magnetic field is currently decreasing in strength.
It's decreased about five percent since 1832, so some have claimed that the Earth's magnetic field may be entering a reversal right now.

Geology School Keywords
Skip footer navigational links

Coastal and Marine Science Centers:  Pacific   St. Petersburg   Woods Hole  
InfoBank   Coastal and Marine Geology Program   Geologic Information   Ask-A-Geologist   USGS Disclaimer  

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:25:26 PDT 2013  (chd)