Deltas

Deltas only form when the rate of deposition exceeds the rate that sediment is removed from the river.

Flocculation is when fresh water meets salts water which produces an electric charge, making sediment coagulate (come together).

The conditions usually needed for Deltas to form...

1. The sediment load to be very large (like in the Mississippi and the Nile)

2. The coastal area that the river empties it's load into has to have a small tidal range and weak currents eg the Gulf of Mexico or the Mediterranean sea.

Cross Section of Delta composition:

Finer Silts and clays are deposited at an angle as they build upwards, building up the foreset beds.

The finest clays are carried the furthest in the river's suspension.

The coarser sands and silts are deposited first.

Type	Example	Characteristics	Reasons for
Arcuate	Nile	-Arcuate is Latin for ‘curved’ -As deposition in the main channel occurs, many distributaries break away from it, causing the river to braid -Have rounded, convex outer margins aka curved shorelines -Their drainage pattern is dendritic (whatever that means...)	-Longshore drift keeps the seaward side smooth
Bird’s foot	Mississippi	-Tend to have one or a few major distributaries near their mouths -Have a broad shallow shelf which deepens abruptly -Named because they grow tall and thin like a bird’s toe	-The receiving basin has currents, which carry sediment away as soon as it reaches the river mouth
Cuspate	Ebro (Spain) I think it looks like a happy dolphin	-Cuspate means a projecting point between 2 arcs -It happens where material carried down the river is spread evenly on either side of the river	-They are pointed like a ‘tooth’ -They’re shaped by gentle, regular but opposing sea currents or longshore drift