Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Conclusion

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: 25:39 - 27:00 (01:21)
Source: Annenberg/CPB Resources - Earth Revealed - 10. Geologic Time
Keywords: "James Sadd", radioisotope, "relative age dating", "absolute age dating", mineral, superposition, horizontality, "cross-cutting relationship", "radiometric age dating", geologist, "rock formation", "geologic structure"

Our transcription: Minerals which contain radioactive isotopes act like tiny clocks inside of rocks, clocks which are reset when a rock is formed or metamorphosed.
Before geologists learned to measure the absolute ages of rocks using radioactive isotopes, they could only establish relative ages using the common sense logic of superposition, original horizontality, and cross-cutting relationships.
They knew that one rock formed before another, but never how old the rocks actually were.
The reliability and accuracy of radiometric age dating is truly impressive.
The results of over half a century of radiometric age dating studies are entirely consistent with the relative age relationships developed by early geologists.
So the science of geology has given us two ways to understand Earth history.
First, we determine the relative age of rock formations and geologic structures and then use these ages to construct a historic sequence of events through time.
Then, by applying radiometric age dating techniques, we determine the absolute timing of these events and measure the rates of geologic change as well.
So not only does our study of geologic time allow us to understand Earth's past, it gives us a historic framework and the tools for predicting the planet's future.

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/09.01.30.html
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:26:16 PDT 2013  (chd)