Deltas
A delta= a feature of deposition- located at the mouth of a river as it enters a sea or lake.
Deposition occurs as the velocity + sediment-carrying capacity of the river= decrease on entering the lake or sea= bed load + suspended material are dumped.
Flocculation= occurs as fresh water mixes with seawater + clay particles coagulate due to chemical reaction= clay settles on the river bed.
Deltas form = rate of deposition excveeds the rate of sediment removal.
In order for a delta to form the following conditions are likely to be met:·
1) The sediment load of the river is very large, as in the Mississippi and Nile rivers
2)The coastal are into which the river empties its load = small tidal range + weak currents= limited wave action and, therefore, little transportation of sediment after deposition has taken place.
E.G Gulf of Mexico and the Mediterranean Sea
Deltas are usally composed of three types of deposit:
· The larger + heavier particles = the first to be deposited as the river loses its energy= form the top set beds
· Medium graded particles= travel a little further before they are deposited as steep-angled wedges of sediment, forming the foreset beds
· The very finest particles= travel furthest into the lake before deposition and from the bottomset beds
Deltas = described according to their shape.
`Arcuate delta (Nile delta) =curving shoreline + a dendritic pattern of drainage.
Many distributaries break away from the main channel as deposition within the channel itself occurs = the river braids.
Longshore drift keeps the seaward edge of the delta relatively smooth in shape.
Bird's food delta he (Mississippi). Fingers of deposition build out into the sea along the distributaries' channels, giving the appearance from the air of a bird's claw.
A cuspate delta is pointed like a cup or tooth and is shaped by gentle, regular, but opposing, sea cuurents or longshre
Deposition occurs as the velocity + sediment-carrying capacity of the river= decrease on entering the lake or sea= bed load + suspended material are dumped.
Flocculation= occurs as fresh water mixes with seawater + clay particles coagulate due to chemical reaction= clay settles on the river bed.
Deltas form = rate of deposition excveeds the rate of sediment removal.
In order for a delta to form the following conditions are likely to be met:·
1) The sediment load of the river is very large, as in the Mississippi and Nile rivers
2)The coastal are into which the river empties its load = small tidal range + weak currents= limited wave action and, therefore, little transportation of sediment after deposition has taken place.
E.G Gulf of Mexico and the Mediterranean Sea
Deltas are usally composed of three types of deposit:
· The larger + heavier particles = the first to be deposited as the river loses its energy= form the top set beds
· Medium graded particles= travel a little further before they are deposited as steep-angled wedges of sediment, forming the foreset beds
· The very finest particles= travel furthest into the lake before deposition and from the bottomset beds
Deltas = described according to their shape.
`Arcuate delta (Nile delta) =curving shoreline + a dendritic pattern of drainage.
Many distributaries break away from the main channel as deposition within the channel itself occurs = the river braids.
Longshore drift keeps the seaward edge of the delta relatively smooth in shape.
Bird's food delta he (Mississippi). Fingers of deposition build out into the sea along the distributaries' channels, giving the appearance from the air of a bird's claw.
A cuspate delta is pointed like a cup or tooth and is shaped by gentle, regular, but opposing, sea cuurents or longshre
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