COASTS


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LINKS
http://www.miracosta.cc.ca.us/home/cmetzler/field_trip/top.html
http://dsc.discovery.com/games/surfing/surfing.html
http://seawifs.gsfc.nasa.gov:80/OCEAN_PLANET/HTML/peril_buoys.html

PARTS OF A BEACH
1.berm-dry portion that builds in summer
2. dune-supplies sand to the beaches during storms
3. swash zone-where waves crash back and forth
4. berm crest-marks the high tide line

DEPOSITIONAL BEACH FEATURES (sandy beaches--sand comes from rivers, bedrock, shells)
1. tombolo-sand bar attached to an island from shore
2. spit-sandy bar that sticks out into the water
3. barrier beach- long thin beach

EROSIONAL BEACH FEATURES (in bedrock)
1. sea cave-from wearing away along fractures in sea cliffs
2. Sea arch--natural bridge
3. sea stack-when an arch collapses leaving a block of rock in the water

WAVES
1. form from wind
2. approach the shoreline at an angle
3. as they come in towards shore they refract to become almost parallel with the shore due to the fact that part of the wave in deeper water moves faster than the part in shallow water (creates a longshore current)
4. break due to the decrease in wavelength, increase in wave height, elliptical motion of orbitals, and decrease in speed at wave base
5. wave size depends on the fetch, duration, and speed of the wind as well as the presence of storms/sea state

SAND MOVEMENT
1. generally sand moves in a zag zag motion due to the swashing back and forth of the waves and the current that moves parallel to the shore called the longshore current.
2. In places where there are headlands and bays, wave energy is concentrated on the headlands due to the refraction of the waves, causing the calmer bays to fill in with sand (pocket beach forms).

HUMAN DEVELOPMENT
sea walls--protect homes but reflect the energy of the wave causing increased wave heights, erosion at the base of the wall and loss of a beach
jetty--interferes with the longshore current causing sand to build up on one side but erode on the other.
breakwater--create calm harbors but eventually the harbors could fill in with too much sand and require dredging