Coastal Processes ~
erosion, transport & deposition
12.1
CA
NC
Erosion
http://geobytesgcse.blogspot.com/2007/08/coastal-processes-erosion-transport-and.html
Erosional processes
• Abrasion = continuous tumbling reduces rock
to sand grains
• Solution = salt dissolves some of the rock
• Scouring = wave swirls at base of cliff &
loosens rock
Erosion
• Erosional processes in action
• http://www.bbc.co.uk/schools/gcsebitesize/ge
ography/coastal/coastalprocessesrev3.shtml
Erosional Features
•
•
•
•
•
Sea cliff
Sea cave
Sea arch
Sea stack
Terrace
Sea cliff
Navassa Island, Caribbean Sea
• Forms when waves erode rock
http://coastal.er.usgs.gov/navassa/photos/ep/hike/CliffE.jpg
Sea cave
Short Sands Beach, Oregon
• Hole eroded at base of cliff
http://web.cecs.pdx.edu/~walpole/pics/kayak/falcon/cave3.jpg
Sea arch
Hawaii
• Sea cuts through headland
http://upload.wikimedia.org/wikipedia/commons/e/eb/SeaArchHawaii.jpg
Sea stack
County Mayo, Ireland
Isolated column
of rock
http://ts1.mm.bing.net/images/thumbnail.aspx?q=1023555809064&i
d=45685568345e0ba48cec1d6807ea14ba&url=http%3a%2f%2fwww.v
isualphotos.com%2fphoto%2f2x4004071%2fdoonbristy_sea_stack_do
wnpatrick_head_ballycastle_1813001.jpg
Sea terraces
Haiti
• Flat platforms at water height
http://www.amishkin.com/wp-content/uploads/2010/03/P1000346-Large.jpg
Features
Transport
• Material eroded by the sea is moved along the
beaches.
Longshore drift
• Longshore drift illustration
• http://www.bbc.co.uk/schools/gcsebitesize/ge
ography/coastal/coastalprocessesrev4.shtml
• Waves approach beach at angle
• Sand moves in zig zag motion
• Creates longshore current
• Current keeps sand moving until it hits a
change or structure, then it drops out.
Longshore drift diagram
http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchamb
ers/GeoBytes%20GCSE%20Blog%20Resources/Images/Coasts/Longsho
re_Drift.jpg
Deposition
• Sand deposits form where amount of rock
moving toward shore is greater than amount
moving away.
Depositional Features
•
•
•
•
Beach
Lagoon
Tombolo
Barrier island
Beach
Emerald Isle, NC
http://www.tripadvisor.com/LocationPhotos-g49113-Emerald_Isle_North_Carolina.html
Lagoon
Vegetation is red; water is blue (satellite image)
Tombolo
Bar that extends
out into ocean,
but remains
connected to
mainland.
web.macam.ac.il
web.macam.ac.il
Barrier Island
http://www.frf.usace.army.mil/outerbanksaerialfligh
t/Index.htm
Barrier Islands
•
•
•
•
Occur on east coast of USA
Isolated dunes become islands
Parallel to shore
Associated features:
– Sound (also called bay or lagoon)
– Tidal inlets
– Tidal flats
– Estuaries
HUMAN EFFECTS ON COASTLINES
Homework
• Read pages 342 - 347
Output
• Draw a block diagram of the east coast and
include the features of the beaches.
• Draw a block diagram of the west coast and
include the features of the beaches.