Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Subduction and Accretion

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: 13:27 - 14:37 (01:10)
Source: Annenberg/CPB Resources - Earth Revealed - 7. Mountain Building
Keywords: subduction, accretion, mountain, orogeny, lithosphere, India, Asia, "ocean basin", collision, "sedimentary rock", "metamorphic rock", "igneous rock", "convergent plate margin", Madagascar, Fiji

Our transcription: Subduction of sea floor is the most common reason mountains form, but it is not the only way.
Another method is "accretion" the joining together of separate land masses.
When two masses of continental lithosphere, such as India and Asia are brought together by the complete subduction of an intervening ocean basin, the collision raises huge mountains.
Sea floor and sedimentary deposits caught in the squeeze are metamorphosed and converted in part to igneous rock.
This process glues the once separate land masses together.
The accretion of two such large bodies of lithosphere as India and Asia is not a common geological event, but there is evidence that much smaller bodies of land are frequently added to the margins of continents by subduction.
Small continental fragments, such as Madagascar and the Fiji Islands are scattered throughout the world's oceans.

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 04:25:57 PDT 2013  (chd)