Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Polarity In Rocks of the Same Age

Skip navigational links
Loading
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: 15:43 - 16:52 (01:09)
Source: Annenberg/CPB Resources - Earth Revealed - 5. The Birth of a Theory
Keywords: "Scott Bogue", paleomagnetism, "magnetic field", "magnetic reversal", USGS, polarity

Our transcription: There was much scientific debate at first because it's known that some rocks can be placed in a magnetic field pointing one way and become magnetized exactly opposite to that direction.
The fact that such rocks existed meant that it was possible that reversely magnetized rocks were simply recording normal magnetic field.
The clinching evidence came when scientists from the U. S. Geological Survey and from other places went on expeditions around the world, collected rocks of different ages, and were able to show that rocks collected from around the world of the same age always had the same polarity.
Rocks that were younger than thousand years old were normally magnetized.
Rocks older than 700 thousand years were reversely magnetized.
This global pattern of magnetic polarity recorded in the rocks is what convinced people that it was the magnetic field itself changing polarity.

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 USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://walrus.wr.usgs.gov/infobank/programs/html/school/moviepage/05.01.18.html
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:25:41 PDT 2013  (chd)