Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Spits and Bars

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: 10:43 - 12:04 (01:21)
Source: Annenberg/CPB Resources - Earth Revealed 24, Waves, Beaches and Coasts
Keywords: "Thomas Hartnett", sand-spit, bar, sand, bay, "long-shore current", coastline, beach, sand-spit, breakwater, dredge, transportation, deposition

Our transcription: Sand-spits and bay-mouth bars are common products of long-shore currents.
What happens is that the sand is being carried along the coastline, the beach sand, and when the coastline reaches, say, a right angle turn, an abrupt bend, the beach will tend to be carried still by that long-shore current straight along the coastline.
So that the beach will start building out in creating an extension of the beach that will not necessarily follow the bend of the coastline.
In this case, a sand-spit has formed off the end of this breakwater.
This wave tank shows how the sand-spit built up.
The waves strike the breakwater at an angle and bend around it into the harbor.
When sand is added, the waves carry it into the harbor where it builds up into a spit behind the breakwater.
To prevent the harbor from being sealed off, and the beach beyond from being deprived of sand, engineers installed a dredge to pump the sand back into the long-shore current, by picking it up in the harbor and dumping it further down the coast.

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/22.01.11.html
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:27:54 PDT 2013  (chd)