Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Magnetic Polarity

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: 22:12 - 23:03 (00:51)
Source: Annenberg/CPB Resources - Earth Revealed - 3. Earth's Interior
Keywords: "James Sadd", "magnetic polarity", magnetism, "magnetic reversal", "magnetic north pole", paleomagnetism, "magnetic south pole"

Our transcription: When a rock is magnetized, its magnetic field is aligned to the magnetic North Pole of the Earth.
This is similar to the way a compass needle points to magnetic north.
This alignment, called "magnetic polarity" is also permanent in magnetized rocks.
In the early 1900s, geophysicists studying lava flows in France made a startling discovery.
The lavas and the big soils underneath them were both permanently magnetized, and their magnetic polarity was identical in orientation.
But that orientation was exactly opposite that of the Earth; that is, the magnetic north pole of the rocks pointed toward the magnetic south pole of the Earth.
This observation was the first clear evidence that the magnetic field of the Earth completely reverses itself.

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)